I am just about ready for my first fill up, does the xB run better on regular gas or would I get a major improvement if I used premium gas? Has anyone noticed a big difference? At the meet on Saturday a couple of people had mentioned that the xB doesnt really start getting great gas milage until I've got a few thousand miles on it (I am just over 200 miles)

Thanks for the info!

Cheers
Rob

 

I have always use regular

 

I wouldn't waste your money on premium, I mean we have a whole 108 ponies on tap...I have had zero problems on regular unleaded and I get it from QT...

 

Just run regular you dont need the extra octane !!!! our little motors are low compression and you would just be wastin your hard earned $$$$$$.
As for mileage mine got progressively better as it broke in ,engines today have extremely tight tolerances and take much longer to loosen up that is why you dont really have a "Break In" period where you have to change the oil after 500 miles
wingsaseagles

 

stick with regular...gas is expensive enough as it is
mine gets around 32 mpg on avg with reg....

 

damn...i always thought it'd be better to use the higher octane. that's what i've been using. huh, time to switch!

 

I'd use regular. I've been averaging 33/34 mpg in my box. I even had a high of 37 once.

 

Just wait till your rolling 18's. . that gas mileage goes away. Best I have gotten is 31ish. but I average about 27-29ish.

I just use regualr gas too...

 

oh yea I'm sure that my mileage will go down once I get them...lol I still can't find ones that I have to have though.

 

use 87 only with that engine. All higher octain is, is harder to burn fuel. It can have many negative effects on a vehicle that is made to run on 85/87 octain.

 

I would only run what is in your manual, 87, unless you have done some upgrades and those upgrades require the use of 89 or above. I used to run 91 in my focus after I had my bottom end bored and had a full race top end. but before that was the case, if I ran anything above 91, I constantly detonated sparkplugs, Autozone loved me.

 

You mean anything below 91.?

 

Ya, ooops, my bad. Anything under 91 I meant.

 

The "octane" rating of fuel is esentially it's resistance to pre-detonation. The higher the number, the more refined it is and the greater resistance to detonation it has.

Detonation or "knocking" arises from the production of an explosion wave in the combustion chamber. This is due to rapid ignition and combustion. A portion of the unburnt air/fuel mixture becomes compressed prematurely, which in turn rapidly increases in temperature until it ignites uncontrollably and almost instantaneously. The shock wave produced has a characteristic of a metallic sound and can vary in magnitude. It can range from a mild form, occurring only at relatively low speed and wide throttle positions (typically known as "pining") to such violent effects that the engine is no longer running in a controlled manner and power output dies.

Now that we know the definition of detonation we need to comprehend that if the temperature of an air/fuel mixture is raised to high, the mixture will eventually explode spontaneously. This is known as spontaneous ignition temperature. But, before this explosion there is an interval called ignition time-lag. If the piston approaching tdc of the combustion stroke takes longer than this period before the spark plug ignites there will be a premature explosion. The longer the time-lag the less chance of spontaneous there is of spontaneous ignition. If the air/fuel mixture is fired at the correct "timed" point and a good flame is achieved power loss through detonation is still possible. The burnt mixture behind the flame front will be at a high temperature and pressure, which will cause compression of the unburnt gas ahead of the spontaneous ignition point. The flame front must move right through the unburnt charge before the end of the ignition time-lag period if not this can lead to overheating and excessive mechanical stressing.

With any fuel the brake thermal efficiency 1 will decrease if the compression ratio is increased. A properly chosen fuel can help diminish detonation. The advances in modern day fuels have extended their ignition time-lag periods and have decreased the spontaneous ignition temperatures, which allows for the use of a higher compression ratio (safely up to 11:1) to be used in the combustion process under complete control. There are also special fuels made especially for racing applications that allow compression ratios so high that the limit is actually dependent upon mechanical aspects of the cylinder head design.

 

damn. reading ^^ is like reading math....I just can't understand it lol. I think i get the gist of it though. thanks for the explanation!

 

So just use 87.

The only thing I wouldn't use is Circle K, 7-11, places like that. I have noticed minor amounts of pinging after using those places. I think that gas prices are close enough between stations that you can use mobil or chevron, shell, or qt. Oddly enough, qt has sone decent gas.