87, 89, or 91???

remember back in the days i read a article from C&D,
it says something like if the engine design specifically for 87 octane...filling other grade of gas will just decrease the performance....


p.s. sorry for my broken english, since its not my first language :oops:

The Scion xB uses Unleaded Gasoline, Octane rating 87 (Research number Number 91) or higher as it says on the Scion Owners Manual. I use 87 (regular unleaded) on the xB. Works fine.

so the manual doesnt specifically recommend which grade?

it says 87 or higher, that's it. and the ECU is programmed to work well with 87 , so if you put higher octane, it probably won't make any difference with a stock scion engine.

it says 87 or higher, that's it. and the ECU is programmed to work well with 87

thats what i wanted to kno....cool...thanks eric :D

The gas prices here in sandiego are 87 octane $1.67 for 91 octane $1.87.

I love this car. Great mileage

i use pemex gas and my xb runs great lol

I've used 93 octane the last two tanks I put in and there is a noticable difference. About 40-50 miles more per tank: about 4 more MPG. That is over 87 Octane which I used for the first few tanks.

I haven't dont the math to find out if it's cost efficient, but it's useful to get those extra miles per tank on a long trip.

-Gage

I think that difference is just in your mind--maybe you have driven differently in the last two tanks?

Honestly, I don't think the different octance ratings will increase mileage on any particular car.

The car uses and will run best at 87 octane...any higher grade you go, you'd just be wasting money.

I think that difference is just in your mind--maybe you have driven differently in the last two tanks?

Honestly, I don't think the different octance ratings will increase mileage on any particular car.

The car uses and will run best at 87 octane...any higher grade you go, you'd just be wasting money.

Well, perhaps so, perhaps not.

Modern cars are designed to adjust themselves for various grades of fuel. Some cars specify 92 octane fuel, but will run on 87 with a reduction in efficiency.

It is possible that the Scion will run better on higher octanes, but you would have to run some comparisons to make certain. You would have to run a set route, maintain set speeds under similar conditions to get good data. Just calculating mileages from one fueling to another isn't accurate enough unless you are a very consistant driver (as in a long commute or somesuch).

George

I think that difference is just in your mind--maybe you have driven differently in the last two tanks?

Honestly, I don't think the different octance ratings will increase mileage on any particular car.

The car uses and will run best at 87 octane...any higher grade you go, you'd just be wasting money.

AGREE!!!
if the car designs for 87 then go with 87, which i think what xB suppose to run...(it's cost-efficient car remember?)
people from my accord club (av6) did the comparasion between different grade of octane...dyno tests turn out 87 gave more horsepower and torque at the wheel than 89 and 91..

I've used 93 octane the last two tanks I put in and there is a noticable difference. About 40-50 miles more per tank: about 4 more MPG. That is over 87 Octane which I used for the first few tanks.

I haven't dont the math to find out if it's cost efficient, but it's useful to get those extra miles per tank on a long trip.

-Gage

I've had SEVERAL cars, and I have noticed this on all my cars.
With the Scion tank being so small, I'd prob run Super most of the time.
$15.00 fill up, better than $42 on an Avalanche!

There are numerous articles in magazines, etc that show/inform us that the difference is pretty much none--just use what your engine needs. There was even an article in Super Street about it!

Of course, people 'think' they get better results from paying more at the pump..afterall the guys at the gas station aren't going to tell you that all you need is 87...hell, they would love to sell JUST 91 if they could. If you guys are putting Premium gas in the ECHO engine...what would you put in something "high performing"?! It's pretty much self explanatory in the owners manual..."87 or higher". Well, they can't say below 87--because that doesn't exist, and they can't say JUST 87 because higher grades will work just as well. Believe me, there is a reason why a Integra GSR/Type R lists "only Premium" in it's owners manual as opposed to an Integra LS which lists "87 and up".

The amount of octane in gasoline has nothing to do with how "explosive" it is, all octane ratings provide the same amount of oomph. The octane actually delays the speed of combustion... so the more octane in the gas the longer it takes to completely burn.

Engines are designed to work on a specific octane rating... the ignition timing is set for it. If you use a high octane on a car designed for a low octane you will decrease the performance because the burn won't happen until the piston as past the regular point of ignition. Bam -- loss of power and efficiency.

If the manual says 87, stick with 87.

I stay away from ARCO though, my car actually runs worse on it for some reason.

Darren

The amount of octane in gasoline has nothing to do with how "explosive" it is, all octane ratings provide the same amount of oomph. The octane actually delays the speed of combustion... so the more octane in the gas the longer it takes to completely burn.

Engines are designed to work on a specific octane rating... the ignition timing is set for it. If you use a high octane on a car designed for a low octane you will decrease the performance because the burn won't happen until the piston as past the regular point of ignition. Bam -- loss of power and efficiency.

If the manual says 87, stick with 87.

I stay away from ARCO though, my car actually runs worse on it for some reason.

Darren

There is a germ of truth in what you are saying, but some of the gaps need to be filled to understand the issue completely.

Octane is a hydrocarbon compound with 8 carbon atoms, hence the "Oct" prefix.
Heptane is a hydrocarbon with 7 carbon atoms, hence the "Hept" prefix.

(for petroleum engineers, yes there are more technical names for these, but let's keep it simple!)

You mix these two compounds to get standard fuels of various octane ratings. 50/50 heptane/octane gives 50 octane, 20/80 gives 80 octane, and pure octane is 100 octane.

These chemicals are rather expensive and you wouldn't want to bear the cost of running them in your car.

Fuels are tested in a test engine. The test engine is actually run by an electric motor for consistant speed. The neat thing about the test engine is that the head can be screwed down to vary the compression ratio. The engine is run on the fuel to be evaluated and the head is screwed down until the engine starts to pre-ignite or "ping". The setting is noted, and then the test is repeated with various mixtures of heptane/octane ("standard fuels") until the same point of pre-ignition is reached. The percentage of octane in the standard fuel that produces the same pinging behavior is the octane rating of the fuel.

What is pre-ignition? Simply having the fuel ignite all by itself without the intervention of the spark plug. You don't want this to happen, as the fuel burns all at once, causing very high pressures in the combustion chamber which can break things. The higher the octane rating, the more resistant it is to pre-ignition, and that is really the only difference that octane makes. High-octane fuel has a slightly smaller flame propogation speed than low-octane fuel, but not enough to make any difference in a real-world engine.

Toyota specifies that they have designed the Scion engine to run on 87 octane fuel. If that is truly the case, you will not get any advantage in running 91 octane fuel.

Nevertheless, some claim that they have better performance or mileage with 91 octane. How can that be? Well, one way this could happen is if they had a tankful of "bad" 87 octane that was actually lower in octane. The engine's computer would adjust the engine to run on the lower octane fuel, resulting in lower mileage and performance, but not doing anything permanently bad. When the person fueled up with 91 octane, the computer simply readjusted to the normal 87 octane specs and produced better performance and mileage.

Another scenario is that Toyota pushed the envelope a bit with the engine computer, which means that the engine actually does benefit from higher octane fuel. There's nothing magical about the number 87 and they might well have designed it for 87.5 or 88.

How do we tell for sure? All we need to do is to get a Scion, put fuel of a known, measured 87 octane in it, and run a set schedule on a test track. fuel the same car up with 91 octane and run exactly the same schedule on the same track. The results will be quite clear.

Another way to do it is for someone to keep long-term records of a vehicle in regular commuter service. The quirks in the data will tend to average out, so comparisons can then be made between the fuels.

For those who feel that one brand of gasoline is better than others, be aware that all the refiners freely trade gasoline back and forth with each other to meet the needs of their retailers. That "high quality" Union 76 fuel you are putting in your tank may well have come from an Arco refinery! :)

George

There is a germ of truth in what you are saying, but ......... That "high quality" Union 76 fuel you are putting in your tank may well have come from an Arco refinery! :)

George

Excellent explanation on it. So when was our assignment due on this again?

I say just keep track of your gas mileage with real calculations (not rounded calculations off the top of you head) and see for yourself but if the factory says 87 then why fight it.

There is a germ of truth in what you are saying, but ......... That "high quality" Union 76 fuel you are putting in your tank may well have come from an Arco refinery! :)

George

Excellent explanation on it. So when was our assignment due on this again?

I say just keep track of your gas mileage with real calculations (not rounded calculations off the top of you head) and see for yourself but if the factory says 87 then why fight it.

I agree, and I'm pumping 87.

I do keep a logbook in which I record maintainance and fuel use. A sudden decrease in mileage is often a precursor of more serious problems. I've only run two tankfuls through the car, with mileages of 28 (city, with my wife driving) and 26.5 (city, with mostly me driving). Not bad for a new car that advertises 30.

George

I think that difference is just in your mind--maybe you have driven differently in the last two tanks?

Honestly, I don't think the different octance ratings will increase mileage on any particular car.

The car uses and will run best at 87 octane...any higher grade you go, you'd just be wasting money.

It's definitely not in my mind, it was right there on the odometer.
As for difference in driving, I cany drive differently if I tried. And I HAVE tried. I gotta get from point A to point B as fast as possible, apparently as my foot wont let me drive any other way.

The ONLY possible reason other than grade of gas is engine breakin. I might be getting better milage as the engine breaks in. Or it may be the gas. Who knows.

And as for the "use the gas the car is made for" and "the manual says 87" - the manual says "AT LEAST 87" which means that is the LOW end of gas to use, not the TOP END. That says to me that if you are cheap, use 87 but nothing less, but the car can benefit from more.

-Gage


-Gage

It is true that you get better gas mileage with time and miles. The dealer told me that i should be able to hit the advertised 30/34 MPG after 4000 miles or so on my Scion.

I shall wait and see. I've been averaging about 28MPG on full tank freeway/city combined. In addition, i've been using Shell gas 87 Octane. Shell is promoting some new stuff in their gas that promotes better gas MPG.

I have 980 miles on my baby, and i shall see how things turn out near 4000 miles.

Its true about getting better gas mileage as you get more miles on. Right now I'm at 5500 miles total and when I filled up my tank before my most current one I got an AMAZING 33.37 MPG! I thought that was a fluke but I just filled up today and I got 33.83 MPG! I thought I drove it a bit harder and used the A/C more so I didn't think I could've topped my previous MPG but I did....in fact, I've even been doing more city driving since I have to drive about 5-6 miles to get to the freeway from my place instead of the 2 miles it took me at my previous place.

The amount of octane in gasoline has nothing to do with how "explosive" it is, all octane ratings provide the same amount of oomph. The octane actually delays the speed of combustion... so the more octane in the gas the longer it takes to completely burn.

Engines are designed to work on a specific octane rating... the ignition timing is set for it. If you use a high octane on a car designed for a low octane you will decrease the performance because the burn won't happen until the piston as past the regular point of ignition. Bam -- loss of power and efficiency.

If the manual says 87, stick with 87.

I stay away from ARCO though, my car actually runs worse on it for some reason.

Darren

There is a germ of truth in what you are saying, but some of the gaps need to be filled to understand the issue completely.

Octane is a hydrocarbon compound with 8 carbon atoms, hence the "Oct" prefix.
Heptane is a hydrocarbon with 7 carbon atoms, hence the "Hept" prefix.

(for petroleum engineers, yes there are more technical names for these, but let's keep it simple!)

You mix these two compounds to get standard fuels of various octane ratings. 50/50 heptane/octane gives 50 octane, 20/80 gives 80 octane, and pure octane is 100 octane.

These chemicals are rather expensive and you wouldn't want to bear the cost of running them in your car.

Fuels are tested in a test engine. The test engine is actually run by an electric motor for consistant speed. The neat thing about the test engine is that the head can be screwed down to vary the compression ratio. The engine is run on the fuel to be evaluated and the head is screwed down until the engine starts to pre-ignite or "ping". The setting is noted, and then the test is repeated with various mixtures of heptane/octane ("standard fuels") until the same point of pre-ignition is reached. The percentage of octane in the standard fuel that produces the same pinging behavior is the octane rating of the fuel.

What is pre-ignition? Simply having the fuel ignite all by itself without the intervention of the spark plug. You don't want this to happen, as the fuel burns all at once, causing very high pressures in the combustion chamber which can break things. The higher the octane rating, the more resistant it is to pre-ignition, and that is really the only difference that octane makes. High-octane fuel has a slightly smaller flame propogation speed than low-octane fuel, but not enough to make any difference in a real-world engine.

Toyota specifies that they have designed the Scion engine to run on 87 octane fuel. If that is truly the case, you will not get any advantage in running 91 octane fuel.

Nevertheless, some claim that they have better performance or mileage with 91 octane. How can that be? Well, one way this could happen is if they had a tankful of "bad" 87 octane that was actually lower in octane. The engine's computer would adjust the engine to run on the lower octane fuel, resulting in lower mileage and performance, but not doing anything permanently bad. When the person fueled up with 91 octane, the computer simply readjusted to the normal 87 octane specs and produced better performance and mileage.

Another scenario is that Toyota pushed the envelope a bit with the engine computer, which means that the engine actually does benefit from higher octane fuel. There's nothing magical about the number 87 and they might well have designed it for 87.5 or 88.

How do we tell for sure? All we need to do is to get a Scion, put fuel of a known, measured 87 octane in it, and run a set schedule on a test track. fuel the same car up with 91 octane and run exactly the same schedule on the same track. The results will be quite clear.

Another way to do it is for someone to keep long-term records of a vehicle in regular commuter service. The quirks in the data will tend to average out, so comparisons can then be made between the fuels.

For those who feel that one brand of gasoline is better than others, be aware that all the refiners freely trade gasoline back and forth with each other to meet the needs of their retailers. That "high quality" Union 76 fuel you are putting in your tank may well have come from an Arco refinery! :)

George

I've only put 91 in my xb since I got it, and I've only gotten 30mpg once. Since then, I've been getting numbers like 24-29mpg. Mine's an automatic, which specifies 30/34mpg. My commute is a 10 mile stretch down highway, and I've recently been keeping the speeds down to 65-70 mph to try and maintain some consistency. The last two tankfuls have netted me about 27mpg.

After reading some info on this thread, I've decided that I will try 87 octane at the next fill-up and post my results. Also, I am running stock wheels/tires/suspension with 32 psi tire pressure at all 4 corners. If I don't see an improvement after running 87 octane, I will boost pressure up to 37 and see if that makes a difference.

If I still get the same 27 mpg, I will go to the dealer and have them check the engine.

Cheers

Guys... comon...... I am confident in your essay writing abilities and facts but this is crazy.......although thank you for the info, I was actually thinking about this topic last weekend.

i'll toss my 2 cents on this subject...

i have an stock auto xB that i run about 50 miles each day, almost all freeway, little to no traffic, averaging 65-80mpg, with a short uphill climb (for those who drive 680 in the bay area, that's the sunol grade)... my first tank was straight from the dealer (unsure of the octane rating)... and averaged 30.9 mpg... (which i was already stoked about coz' i was drving my xterra on the same stretch and got 19 mpg)... i filled up with 76 supreme (91 octane) and got 35.1(!) mpg, which blew me away...

granted, my car is new, and is prolly just getting broken in which might explain some of the improvement, btwn the 1st and 2nd tank... but i never expected to actually exceed the manufacturer specs...

on my 3rd tank now, and it seems on par for the same results... i'll post if u guys want (not much else to think about when driving my box an hour a day, lol!)...

i read some ppl on this board drive 100+ miles per day... any additional insight on the subject?..

My girlfriend lives in Fremont, and I go over the 680 Sunol hill all the time(gotta get a running start!). I hit my all time high of 35.3 mpg last weekend with about 90% freeway, no traffic, no A/C, 70-80 mph. Although, it was right after my first oil change, I don't know if that helped.

My xB is stock auto, and I always use Arco 87 (cheapest and closest to my house). For regular driving, i drive about 30 miles a day in stop/go traffic, and I've never gotten less than 29.8 mpg

good article on kbb.com about when to use premium:
http://kbb.com/kb/ki.dll/ke.kb.sp?kbb.CA;;CA067&95630&395&article_ralph11;article/Ralph

87 inless you are running forced induction....then you need 91

Pemex huh, you run on nova(NO VA), or extra. Thats pretty good I like that.[/quote]

This may be a stupid ? but here it goes...

How are you guys getting this exact decimal number (ex. 33.83 MPG)? I would like to know my exact mileage next time I go to the pump.

~ Exxon 87

i use the trip computer milage divided by how many gallons i put in when i fill up... reset after fill up... :D

Gasheadz!! :shock:

I drive a 2k Civic HB, so its got the god awful sohc nonvtec D16y7 :/. Even though the motor is recommended to run 87 I still run premium. I commute everyday about 45 miles, and it is completely flat (South San Francisco -> Emeryville) During the week I hardly put any city miles on it since work is but a few blocks from the offramp and I try not to do much excess unecessary driving. After running the commute for about 4 weeks averaging 330 miles per tank on regular (until the gas light went on) I decided to give premium a try since gas prices have finally dropped down. I now can go rounghly 375mpg with premium before the light turns on. now for me that is great since the roughly 45 miles extra per tank would add up to roughly 1 saved tank of gas per 2 months(roughly). So 6 tanks a year. But figuring how it does cost me a little extra I'll say 5 tanks per year, or roughly 100 bucks (round $20 a tank). Now I could figure this to be a by product of the increase in airflow to my engine due to mild modifications, i.e. intake, exhaust, header, and that the increase in airflow would allow me to burn the higher octane more efficiently. But who knows, that is just wat I have found in my 2 month study( 4 tanks reg, 4 tanks premium). Also I have read many articles stating that octane from pump is usually lower than advertised, not by a whole lot but u know, anything makes a difference.

I'll pony myself up for this. I drive 150 miles a day for my commute. Generally not as much traffic as I leave later in the day. I'll try to drive conservatively and see what I get with 87 octane & 91 octane. Unfortunately, it is a rough science as any variation in the following can affect results:

Different gas stations
Different pumps
Different weather conditions

In any case, I'll fill up with Chevron 87 then Chevron 91. I'll try to use the same pump so when filling up the automatic stop will give me similar results in volume.

I'll probably be able to reply to this next week. My traveling is going to be all over the map this weekend, so now wouldn't be a good time.

To be honest...I doubt I will see much difference other than about $2 more in fuel costs.

I'll pony myself up for this. I drive 150 miles a day for my commute. Generally not as much traffic as I leave later in the day. I'll try to drive conservatively and see what I get with 87 octane & 91 octane. Unfortunately, it is a rough science as any variation in the following can affect results:

Different gas stations
Different pumps
Different weather conditions

In any case, I'll fill up with Chevron 87 then Chevron 91. I'll try to use the same pump so when filling up the automatic stop will give me similar results in volume.

I'll probably be able to reply to this next week. My traveling is going to be all over the map this weekend, so now wouldn't be a good time.

To be honest...I doubt I will see much difference other than about $2 more in fuel costs.

i look forward to seeing your results.....

i have been running 89 octane in mine since i got it and was wondering how it would do with other grades.....

The guy who sold me my Scion was telling me something along the lines of, if u put in a higher octane than 87, in time some kind of deposits will collect in your gas tank. I honestly can't remember what he said exactly, and even he didn't sound THAT confident about it, so i dunno. :shock:

I hear this all the time! Putting in higher octane does NOTHING for gas milelage. Higher octane is just fuel more resistant to detonation. The compression of the Scion is 10.5:1 which could call for high octane, but it's tuned for 87 octane. The only thing higher octane will do is keep your car from pinging. But the Scion doesn't have detonation problems with 87 octane, so there's no point to using higher octane unless you have extensive mods or high milelage. There's nothing anyone can say that will make high octane=higher milelage per tank. I've heard so many people make this claim which is very misinformed. My buddy is a tech at Honda, and he hears customers (mostly ricers) say that about their Civics all the time. He just laughs at them. Read up on the subject. Maybe you just think you're getting better mileage because the gas is more expensive and you're driving more conservative. Maybe the weather was better. Maybe you went up fewer inclines. Maybe you caught more green lights and drove on the freeway more. Maybe you recently installed i/h/e. Maybe you carried less people in the car. Get what I'm saying? There's too many factors for anyone to make this claim. I trust the lab studies more than what anyone says they have done on a few tanks.

as for octane and power, i noticed when i had my 96 Sable [6 cylinder] that the engine felt stronger with a higher octane fuel....i could feel the difference in acceleration between the two....

in my xB, i have been using 89 since i got it thinking i might get a [b]little[/]more power from a higher octane gas.....

i would like to try 87 but i am concerned about starting to use it now since i have been running 89 all along....

any thoughts on this would be appreciated....

as for octane and power, i noticed when i had my 96 Sable [6 cylinder] that the engine felt stronger with a higher octane fuel....i could feel the difference in acceleration between the two....

in my xB, i have been using 89 since i got it thinking i might get a [b]little[/]more power from a higher octane gas.....

i would like to try 87 but i am concerned about starting to use it now since i have been running 89 all along....

any thoughts on this would be appreciated....


How many miles are on the Sable? Older cars usually do get more power from higher octane due to the carbon deposits raising the compression. On newer cars it shouldn't make much of a difference if any.

higher octones wont make any difference on gas mileage...

some guy in our accord club dyno the car using different octanes...it shows 87 out perform higher octanes...so if the car is design to use 87 then use 87....

This could be mental but the only thing i have noticed is that when i stopped using 87 and went to 89 the engine idles smoother. At 87 it always seemed like it wanted to stale. After all at 10.5:1 compression seems aweful high to be running cheap gas. Yes I know its tuned for 87, but geez, 10.5:1. Does timing affect it that much that you dont have to run super? Especially under heavy throttle?

I do agree with Darren. Stay away from ARCO, or at least the one by my house. My cars run horrible on it.

This could be mental but the only thing i have noticed is that when i stopped using 87 and went to 89 the engine idles smoother. At 87 it always seemed like it wanted to stale. After all at 10.5:1 compression seems aweful high to be running cheap gas. Yes I know its tuned for 87, but geez, 10.5:1. Does timing affect it that much that you dont have to run super? Especially under heavy throttle?

I do agree with Darren. Stay away from ARCO, or at least the one by my house. My cars run horrible on it.


It shouldn't effect the way the engine runs because the ECU will adjust timing to make the car run exactly the same whether it has 87 or 91. My xB runs just perfect on 87.

as far as mpg, w/ the Injen intake, Tanabe axle-back exhaust, 2" Spy drop, and 17" wheels, I get just over 30 mpg doing 80 mph on a 54 mile one way commute. now that I've had the intake and exhaust modded, my mpg has gone own due to the lead that has settled in my right foot. oh, and I have a 5 speed.

I usually average 34-36 mpg when I keep it at 70 mph.

squirrel

i'll toss my 2 cents on this subject...

i have an stock auto xB that i run about 50 miles each day, almost all freeway, little to no traffic, averaging 65-80mpg, with a short uphill climb (for those who drive 680 in the bay area, that's the sunol grade)... my first tank was straight from the dealer (unsure of the octane rating)... and averaged 30.9 mpg... (which i was already stoked about coz' i was drving my xterra on the same stretch and got 19 mpg)... i filled up with 76 supreme (91 octane) and got 35.1(!) mpg, which blew me away...

granted, my car is new, and is prolly just getting broken in which might explain some of the improvement, btwn the 1st and 2nd tank... but i never expected to actually exceed the manufacturer specs...

on my 3rd tank now, and it seems on par for the same results... i'll post if u guys want (not much else to think about when driving my box an hour a day, lol!)...

i read some ppl on this board drive 100+ miles per day... any additional insight on the subject?..

hey Snuppy

keep us posted on the 76 gas mileage....

i used 76 when i first got mine and seemed to get the best mileage with it also.....

i am curious to see if you continue to get the high mileage on your xB!!

basically this is what i've learned about gas and octanes. the reason some cars specify 87 while others specify 91 is the timing that the car is set to. so basically if your car says 87 put 87 because 91 will not really have any advantages. to the people who say they get better gas mileage it could be for many different reasons. your car is breaking in, you drive less aggressively, and just too many factors. but you only need 91 if you advance the timing on your engine to prevent any engine knock (detonation) thats why race cars run 100+ octane fuel (race gas) because the engine is specifically tuned to run with that type of fuel.

alrighty... here's what i've got so far... since my last post i've filled up two more times (for a total of 3 tanks of 91 octane supreme from 76)...

347.6mi/9.902gals= 35.102mpg
346.3mi/9.891gals= 35.012mpg
350.7mi/9.992gals= 35.098mpg

just filled up with 87 octane from the same 76 station... and will do so for the next few tanks to see if there is any significant difference... i highly doubt there will be any significant change, coz' what everyone on this thread is saying makes sense... at least i can say it makes trips to the gas station a bit more "exciting"... :lol:

i should add that the weather has been craptacular lately, so that might skew things a lil' bit...

alrighty... here's what i've got so far... since my last post i've filled up two more times (for a total of 3 tanks of 91 octane supreme from 76)...

347.6mi/9.902gals= 35.102mpg
346.3mi/9.891gals= 35.012mpg
350.7mi/9.992gals= 35.098mpg

just filled up with 87 octane from the same 76 station... and will do so for the next few tanks to see if there is any significant difference... i highly doubt there will be any significant change, coz' what everyone on this thread is saying makes sense... at least i can say it makes trips to the gas station a bit more "exciting"... :lol:

i should add that the weather has been craptacular lately, so that might skew things a lil' bit...

thanks for the update Snuppy!

that is excellent mileage! are you doing mostly freeway driving as you mentioned earlier? i really have not done much freeway driving and when i do, it is going out Lancaster way and there are numerous long grades so it does not get the highest mileage on those trips...

no problemo yanges...

yah, it's almost completely freeway with virtually no slowdown or traffic to deal with... it's almost relaxing (if only i wasn't on my way to work)... i'll also add that i ride solo to and fro so that prolly helps keep the mpg on the higher end... i use my xterra on weekends (unless there's a meet) so that'll also help keep things consistent...

Ok, well here are my results (unfortunately, I don't have the gas amounts & miles driven as I lost the piece of paper...i know, my bad :cry: )

On 87 Octane: 34.5 mpg
On 91 Octane: 33.7 mpg

For this time frame, I pretty much tried to keep the revs under 4k. This allowed me to easily go the speed limit on the highway in 5th gear. I hit 70 a couple of times, but always tried to keep it 65 mph. I got stuck in traffic twice (damn San Mateo bridge), once on each grade of fuel. So the milage probably could have been better, but at least the delays were equal, both around 45 minutes. So not as nice of a manner as I would have liked to display my findings, but I would say 87 is the obvious choice. For me to loose any milage with an additional expense, no value what so ever.

I'll be interested in seeing Snuppy's results with regular.

just so i don't leave anyone hanging on this... i've been using 87 (from the same 76 station) the last few weeks, unfortunately during the xmas season, i've been carting around more ppl and cargo (xmas gifts) everyday, so really no point in comparing the mpg stats... however, considering i typically had one or two other ppl with me AND varying amounts of cargo AND sh!tty traffic jam parking lot conditions, i'm still averaging about 32.5 mpg... still pretty darn good, all things considered...

i use the trip computer milage divided by how many gallons i put in when i fill up... reset after fill up... :D

do you top off until gas leaks out or what? because those nozzles pops at different times. even if it's the same nozzle. So unless every that posts up there numbers here tops off your tank till it spills, you numbers ARE NOT ACURATE. i'm not calling you guys liars but that's how the nozzles works. so that's why some of you are getting more when switching to 91 or 87. But what actually is happening is just simply because u got more/less gas for the "fill-up" tank.

CORRECT ME IF I'M WRONG.

my 2cents

yah, ur probably right... the pop off times do differ, however, i'm pretty sure that they don't vary so much so that it'll dramatically screw with the results... my #'s are pretty consistent... and even with a variance of 2 mpg either way, i'm still impressed with what my lil box gets... (my other car is an suv that gets 20mpg at BEST)...

i'm assuming most of our mpg tests are done as quickly and painlessly as possible which means as un-scientifically as possible... if anyone wants to top off their tanks, be my guest... i dont' feel like cleaning gas off my quarterpanel & wheel... :wink:

happy holidays!..

Well considering the fact that gas is classified by its resistance to combustion (91 being the least resistant to combust) and the fact that the engine is running at a compression ratio of close to 10.5:1 Id recommend 91 octain if you are the heavy driver thinking that the xb is the fastest thing in the world. If you do not put a load on your car a lot then if u wanna save a few cents, 87. The computer cannot determine if u have 87 or 91 ect. But it will sence all the knocking from the detonation of u put 87 and decide to go full throttle up a mountain.