So about 3 days ago my gas mileage has been really bad, i have had a K&N cold air intake for about a year and no problems, my driving habbits are pretty steady once in a while i step on it, but if never had this problem.. I dont know if i should take it to the dealership because i believe the cold air intake voided the warranty unless im wrong. any suggestions?

How bad was your mileage(post numbers)? the intake didn't nessesarily void your waranty, look at this:

http://www.scionlife.com/forums/viewtopic.php?t=55338

well i cant give exact numbers... may be i explained it wrong as well... here's what happened, I filled up started driving and the needle on the gas meter started dropping faster than normal, then today i was stopped at a light and it started to go down very little but it went down.

You gotta have more backing than that. Also remember, your fuel tank is not shaped evenly. It doesn't drop consistently. It drops quickly at some points and very slowly at others.

calculate your gas milage and see if there really is a problem

yea... you could be on a hill and you noticed that it was dropping.. but if you on a different hill it could have rised... you know what i mean... try to gauge your mileage then you will get a better measure.. now if you're only getting like 170 miles to the tank.. then you might have a leak...because even if you take it to the dealer.. they're gonna want ot know numbers...

been using the same gas brand? any change in driving habits?

what gas brand are you using btw?

So about 3 days ago my gas mileage has been really bad, i have had a K&N cold air intake for about a year and no problems, my driving habbits are pretty steady once in a while i step on it, but if never had this problem.. I dont know if i should take it to the dealership because i believe the cold air intake voided the warranty unless im wrong. any suggestions?

Like everyone says, try to actually record this problem, see what kind of mileage you're really getting. And no, your CAI did not void your warranty. This is a myth.

Actually i alternate between shell gas and arco!! i no that arco isnt good to use but if i only have a few bucks for gas then i try to get as much as possible.. lol... my driving habits are the pretty steady! It could be the hill theory, i have now learned that the intake did not void the warranty i just thought that any mods to the engine would void it!! lol thanks for your help guys i really appreciate!!

sorry dont mean to thread jack but this has something to do with this post

i disconnected the negative part of my battery a few times and am wondering if that resets the cars ECU fuel/ratio computer. cause now i have horrible gas mileage. fillin up once a week

i have an I/H/E setup and i get at least 250-270 miles to the tank.. not the whole tank.. but to the point where i fill it up and when the light comes on..

Once again, post numbers. It might not be as bad as you thought.

Bad gas, a A/F sensor going out, just alot of stop and go traffic with a standard.....could be many things. I had an A/F sensor where I was gettting like 10 MPG cause it was going out on my car and I just put my stock air box back on when I turned it in. Than had anouther check engine light a few months later, apparently running realy rich clogged up my cat.

hey thats some good info that you're giveing out, but how about if we're going to a turbocharge kit to our tcs what kind of gas mileage are we going to get, cause if we get less than when its stock i might keep my tc stock then because since gas price is still high and i dont want to be gasing up every other day of the week, so can you tell me about this question .

you'll have to give us some real mpg numbers, not just a feeling.. need hard data on this one

ok in city i get about 21-25 mpg and on highway 25-29 mpg but how will the turbo charger change the gas mileage?

hey thats some good info that you're giveing out, but how about if we're going to a turbocharge kit to our tcs what kind of gas mileage are we going to get, cause if we get less than when its stock i might keep my tc stock then because since gas price is still high and i dont want to be gasing up every other day of the week, so can you tell me about this question .

If you're worried on gas then pass on forced induction. Once you go boost that gas has to be premium, even the TRD supercharger. In regards to gas I always have money set on out just for that so that'll be one less worry, work that in your budget man. I do have some times where I get on it here and there so gas mileage will vary.

are you sure i have to change to premiun if i go turbo because some of my friends have cars with turbo and they're running it with regular, but i think it will be worth the money so i think i can deal with it

I've taken a look at factory cars that are turbo and the recommended gas is premium. If they're running regular then they are not getting the most out of their turbo setup. Then again I don't have a turbo car so my knowledge isn't up there on the subject but heck, my friend had a ZPI stage zero and was running premium.

Your friends are knocking their engines with a lower octane gas, forcing the engine to retard timing.

Zebman, right on bro, it IS a lie and you DO need boost.
On to gas mileage. What is everyone smoking? In my Tc stock driving like a bat out of hell I was getting 330-350 miles per tank. Now with 40 height 18's that are 2 inches wider than stock I'm getting only 300-310 (which I am ____ED about btw).
I think someone jacked this thread with regards to forced induction, but the truth is with a turbo and the right management system (computer) for tuning you can lean that b*tch out, retard the timing below 3k rpms and get 35 mpg if you want to!

if i have to change my gas and than dont i have to change my fuel injector, because the stock fuel injector are already used to the regular gas and if i do change to premiun gas wouldnt the injector be clug up because the high the gas rating the thicker it is right? but thats what i'm thinking...

chai, buddy, not even close. octane has to do with combustion under compression. The more octane your gas has, the less chance it will combust under pressure, usually before spark, which results in engine knocking. Since FI runs higher compression, you need more octane to prevent premature combustion. you would get different injectors typically to pump in MORE gas, whatever octane that gas may be. check this out:
http://auto.howstuffworks.com/question90.htm

that was some good info bozuzu, this might be dumb but can you change to premiun gas while running on the stock motor and will it cause any problem

you can but it's a waste of money. The only reason you'd need it is for a higher compression motor. Expensive cars typically have higher tolerances, meaning they're machined to perfection, and higher horsepower, which is due in part to having higher compression, which is why expensive cars typically require 90+ octane. The only real danger is running too low of an octane, not too high. The argument has been made also that you might loose power and efficiency because you won't be burning all of the hydrocarbons in a cycle (by using a higher octane than necessary).

What is the normal range for the tC on a single tank of gas? I decided to start tracking my miles per tank with the trip counter and my last couple of readings were around 350 to a full tank. The most recent reading was 300 miles to 12 gallons, which is 25MPG. Guess that's pretty average, but I just wondered what anyone else is getting.

yeah rodc I posted that earlier, on stock wheels and tires I was getting 350 usually, now with 40 height 18s (quite a bit larger diamter) I'm getting 310. If I milked it and drove it like an old lady I'd prolly get 320, but of course with the TRD suspension and hotchkis sways and rt-615 tires that's impossible. . .

The best way to estimate your gas mileage: Fill up your gas tank to the point of the first shut off at the pump, do not force more gas in there. Reset your mileage. Return to the same gas station when you are on E. Fill up to the exact same shut of point. Record the number of gallons. Now divide the amount of miles driven by the amount gallons you just filled your gas tank with.

Also, a lot of variables may be causing for you have low gas mileage. First thing I would check is whether you are running rich. Pull out your spark plugs, they should be a light brown color or so, if they are black then you are indeed running too rich. Go to Toyota and have them check your sensors.

how would the spark plug look like if its running too lean

chai, if it were running too lean it would be a gift from god, and unfortunately that's not a possibility. The irony of VVT and emission control devices is they always default to destroy the environment mode when not working properly. :eyebrow:

how would the spark plug look like if its running too lean

You plugs would be white. Running lean is just as bad if not worse than running rich. The leaner you run the hotter your engine is, you can get piston,cylinder damage, etc.

Read this, great article to read spark plugs. While the article is for bikes, the same concepts apply to cars. Click links for pics.
http://www.dansmc.com/sparkplugs1.htm

what's awesome there is that while my post what mostly accurate, Menace steps up and actually answers the question. Nice article.

can any 1 tell me y my car is using more gas than it normaly do? ok just the other day i gased up my car full and its been two days and now my gas is on the 3/4 full tank mark and my mileage is reading at 71 miles but before this happen my mileage would be around 90-115 miles when it hit that mark and thats with my exhaust on too (0nly part i add to my car). But everything runs great on the car and the gas is only the thing thats killing me right now and i ask everybody i know who work on car and they told me that i might be running to rich but i checked my spark plug and they seem fine to me so can anybody out there please help tell me whats wrong with my car.

Could be the gas, could be excessive idling or more aggressive driving on the last fill. See if the problem is consistent (more than one gas tank), if it is, then check your plugs. Your plugs wouldn't show it right away.

it could just be your gauge... not an actual engine problem..

How would it be the gauge?

You can never say anything about MPG without at least two complete fills, mileage readings, and exact gallons pumped from either the pump or the receipt.

This assumes NO "topping off"!

i was just woundering if i change gas will it help with the gas milage cause i talked with some techs and they said changing frum regular 87 to med. 89 or pre.93 might help the car with the gas milage but not 100% sure if it does so can anybody tell me it changing gas can help with the gas mileage?

damn man...you guys are getting some good mileage...i'm getting about 22 or so miles per gallon...and i mostly drive freeway miles

Hello everyone, well I also been getting horrible gas milage, every since I took out the cold air intake I been getting like 27miles per 1/4 of a tank which translates to 108miles per tank. I already check for leaks and there are none and all my hoses are connected. I took it to the dealer but they said to check it, it was going to be $100.00 weather I fix it or not. :tap: So they checked the car and took my money and told me that it was the 0xigen sensors and it was going to be $800.00 to fix it. :tap: Now I don’t think that’s the problem anyone has any ideas?. there is also a weird Vibration When the car is decreasing speed. Thank you all for your time.

well taker do u have any aftermarket parts on ur car cause that might also b a problem cause i have a HKS HiPerformance exhaust on my car and it sucks alot of gas cuz i think the own bfor me didnt keep tha car up to maintance cuz when i bought tha car i drove it for a few weeks then i had to change the oil to it and it was dark as hell and then i knew that the deal and old owner didnt even touch the car so i had to diagnose the problem myself and firuge out that since i have the exhaust on its running to lean and thats why i had to buy an cold air intake just to make the car run better but it help the car not to run lean now but its still eating alot of gas and i'm still figuring out how to fix this and if i do i'll let u guys know how to fix this gas problem.

Thank you Chai, and now that you mention it, when I had the Cold air intake, the car use the breath a lot better and use to sounded great and when I switched back to stock it feels that its not breathing at all. Well it looks like I’m putting the cold air intake back. I just wanted to keep the car stock in the engine department, my car is way 2 attractive as is and I don’t want to give the cops a reason to give me a ticket. But what I do have and I’m planning on putting in, is the S-pipe and the mid-section pipe. Do you think that this would help without the intake. Thank you sir.

stop punching it ....

well taker, its like working with one hand if u upgrade one thing u'll have to upgrade the other part too cuz it all work together but thats my opion and if u want to put tha s-pioe on go ahead but before u do anything u'll have to do sum research on what it'll happen and what it can effect, so do sum research on it and c what happen

power mods aren't the only thing that affects gas mileage. changing the suspension, changing the alignment (for example my car is aligned to perform better not for optimum tire wear and economy), bigger/heavier wheels/tires, dirty air filter, bad/old motor oil, etc, etc..all will affect gas mileage to some extent.

thats some true statement, but let me ask a qusetion if ur going to change gas frum regular to preinum do u have to change tha FI (fuel injector) or use the same one that came with tha car?

thats some true statement, but let me ask a qusetion if ur going to change gas frum regular to preinum do u have to change tha FI (fuel injector) or use the same one that came with tha car?

Why do you want premium gas? Unless your going F/I (forced induction) or running a built motor (I'm not even sure if you would need premium for a built motor?) but on our cars regular to premium won't make a difference other than you paying more at the pump for nothing.

no tha only reason i'm asking is b cuz i'm planning on turbocharging my tc and i heard that if anyone upgrade anything u'll have to change ur gas, but i think it'll help cuz its kinda thinner and i'll give a better outgoing performance number.

For choosing what octane the tC uses, basic 87 octane is preferred. for FI cars in general 91 (and up) octane is needed.

Driving habits do affect your gas mileage. I know because the first week of driving the tC i was doing 18MPG because I was so use to my 300zx TT. Now I "don't" push the gas too much and now I get at least 25MPG. The heavier foot you have, the more you will use up gas.

Have your car do the closest mileage maintenance, keep using the same octane gas from the same gas station, record the total mileage per fill up along with total gallons of gas filled. Use those numbers to find your miles per gallon. Come back to us and someone will tell you if it does have a problem.

Yes, the previous owner could have messed up the car before you bought it, so do as much as you can to make sure all parts are in proper working order. This has a high price, but what do you expect from a used car.

Oh and back to the Forced Induction question, if you're trying to save as much money as you can by using the cheapest fuel possible, FI is not for you. Period.

I hope this helps.

no tha only reason i'm asking is b cuz i'm planning on turbocharging my tc and i heard that if anyone upgrade anything u'll have to change ur gas, but i think it'll help cuz its kinda thinner and i'll give a better outgoing performance number.

Well yeah like I was saying if you plan on going turbo or sc then you will need to run premium and I believe you may have to get bigger injectors. But until you go F/I stick with regular octane it's not going to affect the cars performance, even if it did it wouldn't be a noticeable difference.