Gas Mileage

cheshirecat · Post by **cheshirecat** » Tue Dec 05, 2006 9:56 am

The gas mileage in the soob has taken a piss poor turn. I'm about to fill up and I've gone 200 miles with average->occasionally hard driving. Any ideas on why this might have occured? I can think of a few possibilities but let me know what you guys think....

Post by **complacent** » Tue Dec 05, 2006 10:36 am

Oxygenated Gasoline... It sucks the big one here, every winter

cheshirecat · Post by **cheshirecat** » Tue Dec 05, 2006 10:52 am

explain

Mr Kleen · Post by **Mr Kleen** » Tue Dec 05, 2006 11:05 am

there is a different gas blend during the winter months. they add oxygen to help with emissions, but it just ends up diluting the gas and you burn more. the google will have more info if everybody else is as lazy as I am...

Post by **complacent** » Tue Dec 05, 2006 11:07 am

here

and

here

and

here

and

here

Basically, they "water down" the gasoline in the wintertime, using O2 to do it. The "reduced emissions" comes at a MPG hit. The regulatory groups involved claim a "1 to 3 %" reduction in mileage... IRL it is much worse than that.

sirwilliam · Post by **sirwilliam** » Tue Dec 05, 2006 12:07 pm

cheshirecat wrote:The gas mileage in the soob has taken a piss poor turn. I'm about to fill up and I've gone 200 miles with average->occasionally hard driving. Any ideas on why this might have occured? I can think of a few possibilities but let me know what you guys think....

Aside from the "Winter Gas", have you tweaked the tune on your car recently?

Post by **Sabre** » Tue Dec 05, 2006 12:15 pm

Yep, Oxygenated gasoline sucks, esp. with turbo cars. One other thing to think about is that the colder air expands a good bit more in your engine, so you have to use a little bit more fuel to keep your AFR's. Depends on how your car is setup though wether it will compensate like that.

sirwilliam · Post by **sirwilliam** » Tue Dec 05, 2006 12:29 pm

Sabre wrote:Yep, Oxygenated gasoline sucks, esp. with turbo cars. One other thing to think about is that the colder air expands a good bit more in your engine, so you have to use a little bit more fuel to keep your AFR's. Depends on how your car is setup though wether it will compensate like that.

23 degress at 5AM and my boost cut on me

do not like that at all. Never did that on my other tunes

Libra Monkee · Post by **Libra Monkee** » Tue Dec 05, 2006 3:01 pm

Is there any fuel additive that can be used to offset the amount of suckage caused by the ethanol?

Post by **Sabre** » Tue Dec 05, 2006 3:03 pm

Will: Yep, time to turn down that boost! I'm guessing you wpiked bad b/c of the cold air.

Chuck: Not sure!

Libra Monkee · Post by **Libra Monkee** » Tue Dec 05, 2006 3:23 pm

Crap, time to get the chemistry set. Once methanol bonds to ethanol they cancel each other out, right?

Mr Kleen · Post by **Mr Kleen** » Tue Dec 05, 2006 3:51 pm

octane booster?

Cereb Daithi · Post by **Cereb Daithi** » Tue Dec 05, 2006 4:31 pm

i think that there really are times i do sort of enjoy not having a turbo

Mr Kleen · Post by **Mr Kleen** » Tue Dec 05, 2006 4:40 pm

more power, more problems

Post by **Sabre** » Tue Dec 05, 2006 5:13 pm

Mr Kleen wrote:more power, more problems

lol, ain't that the truth!!!!!!

cheshirecat · Post by **cheshirecat** » Wed Dec 06, 2006 10:29 am

or just more money....

zaxrex · Post by **zaxrex** » Wed Dec 06, 2006 10:23 pm

The crux of the problem comes out to energy density and stoich point of your fuel.

Both methanol and ethanol have lower specific energies (but higher octane ratings). That means that you have to add more fuel to get the car to see 14:1 because the alcohols run about 10:1 stoich and has less energy than regular gas.

If you have the ability to tune your car, you can run fuel leaner due to the knock resistance of the alcohol aditive, but that will increase the operating temp of the engine. In the cold weather, that won't be a problem because the radiator will be working at higher efficiency and you will probably have the heater on.

sirwilliam · Post by **sirwilliam** » Thu Dec 07, 2006 7:35 am

zaxrex wrote: If you have the ability to tune your car, you can run fuel leaner due to the knock resistance of the alcohol aditive, but that will increase the operating temp of the engine. In the cold weather, that won't be a problem because the radiator will be working at higher efficiency and you will probably have the heater on.

"Uh, honey...looks like I am going to have to upgrade to a FMIC and upgrade my radiator to keep up w/ the new gasoline."

chicken n waffles · Post by **chicken n waffles** » Thu Dec 07, 2006 7:57 am

i'm still on the tank on which i received a tune last weekend (read: been stomping on it every chance i get), and i've noticed that not only has my mileage NOT decreased, but in fact i'm going to get about 40 miles MORE on this tank than a regular tank consisting of the occasional spirited acceleration mixed with granny driving.

Mr Kleen · Post by **Mr Kleen** » Thu Dec 07, 2006 8:51 am

chicken n waffles wrote:i'm still on the tank on which i received a tune last weekend (read: been stomping on it every chance i get), and i've noticed that not only has my mileage NOT decreased, but in fact i'm going to get about 40 miles MORE on this tank than a regular tank consisting of the occasional spirited acceleration mixed with granny driving.

see, they WANT to be driven hard!

chicken n waffles · Post by **chicken n waffles** » Thu Dec 07, 2006 9:37 am

subaru wants me to die, apparently.

well, if i gotta go, it might as well be with the only girl i know who isn't a whiny, blood-sucking demon.

Mr Kleen · Post by **Mr Kleen** » Thu Dec 07, 2006 9:47 am

chicken n waffles wrote:well, if i gotta go, it might as well be with the only girl i know who isn't a whiny, blood-sucking demon.

QFT

avriette · Post by **avriette** » Thu Dec 07, 2006 1:19 pm

cheshirecat wrote:The gas mileage in the soob has taken a piss poor turn. I'm about to fill up and I've gone 200 miles with average->occasionally hard driving. Any ideas on why this might have occured? I can think of a few possibilities but let me know what you guys think....

bad o2 sensors, clogged cat, leaks in various manifolds and piping, dirty or deformed spark plugs, clogged fuel filter, clogged air filter... that's probably too drastic for it to be alignment, but subtle alignment changes can also affect mileage. are your tires properly inflated?

Is the car otherwise acting normally? No new sounds or smells? No misses? I notice it's gotten really cold in the last couple days, pretty quickly. How long has it been doing this?

We typically are close to empty at 260. The light comes on around 220-240, and we know we've got another 30 miles or so to go before the car quits.

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