Poor Gas Mileage for Tahoe LT 2008

[Ed Alexander]

Hey all, I bought my 2008 Tahoe LT a year ago however I did not really drive it in the summer as it was off the road. When I put it on the road in September (Living in New York) I was getting average 12-14MPG with 89octane gasoline.. Had the A/C on most of the time as September was hot.
I decided to put in E85 to test it in the past 2 months on and off. Performance I noticed was not that good as it was harder to start my tahoe and gas went down to about 11mpg. I just let the gas run under 1/4 tank and put in 93.

Question I have is should I see a drastic change in MPG immediately or will this take a few more fillups to see results?
I tried almost everything I could to see even idling mpg which when i reset the average mpg on the dash it should 6-8mpg with the ac running.
I tried everything I read on the forums...
I have my tires at 32psi,i run recirculation,changed air filter, changed all spark plugs, i dont have anything in the truck to weigh it down.

 

[Foggy]

It will take about 50 miles for the computer to alter the fuel and timing info
between the E-85 crap and real gasoline... Just give it some time.. Remember you
still have 1/4 tank of E in there.. So on the next fill up you should be back to your
normal gas mileage

 

[Ed Alexander]

ok awesome!~ thanks

 

[avalonandl]

Your wasting $ with 93 octane. The 5.3 runs fine on 87 octane

 

[avalonandl]

Edit: e 85 really hurts your gas mileage

 

[Ed Alexander]

thats really good to know.... thanks for the advice

 

[swathdiver]

I decided to put in E85 to test it in the past 2 months on and off. Performance I noticed was not that good

By switching back and forth, you never let the E85 get up to full strength and maximum power. It takes 3-5 tanks to get up to an 80% octane level, if that's what the pumps are delivering.

Your vehicle is rated for 14 city and 20 on the highway burning gasoline. It is rated for 10 city and 15 highway burning full strength E85.

If the price is low enough, you can actually reduce your cost per mile burning E85 or a mix of gas and ethanol.

My truck gets its best mileage burning a mix that delivers an alcohol content of between 16% to 22% or so. This also delivers its lowest cost per mile to drive.

These motors love to burn it, it's like cheap race gas.

 

[Ed Alexander]

so u recommend using 87 and every 4x or so filling up with e85?

 

[SUMTOY2]

Driving in the heat with ac on will kill your mpg,especially in stop and go traffic. My 08 gets so so mileage around town. But when I go from Arizona to California I get about 475 miles to the tank.

 

[Ed Alexander]

what i am now getting is 13 mpg after figuring everything out. I took out my rear 2 seats, making sure i have 32psi tires, i put in 87 gas from BJ's.

 

[George B]

so u recommend using 87 and every 4x or so filling up with e85?

He is recommending putting a mix of 87or 89 and e85 in at each fill-up. If you get the mix right they run well and the mileage is good.

I disagree that they run fine on 87. They run ok and it won’t hurt. I feel the performance on it is subpar and prefer 89 or E85 in my 2013. If you feel it runs fine then go with it.

 

[Bill 1960]

what i am now getting is 13 mpg after figuring everything out. I took out my rear 2 seats, making sure i have 32psi tires, i put in 87 gas from BJ's.

You haven’t said what kind of driving you do. City / highway, flat/hilly, short drives or lengthy ones. Your mileage may be excellent if it’s short city drives, or terrible if you’re driving 55 mph on a flat highway.

 

[Ed Alexander]

I casually drive. So I have a combination of highway and local driving. I have been using 87 gas now for for a while and getting 13mpg steady in the summer. with A/C blasting at 60 degrees. I also just took out the 2x 3rd row seats so that may also get me a little better mileage.
At this time I AM NOT putting e85 into my tank.

 

[Ed Alexander]

For E85 I think i get better gas mileage in the fall/winter but i need to test it as I just got this truck last year.

 

[Leevon]

There is an alcohol content sensor that is finicky. Find someone with the right scan tool to do a re-calibration. There are a couple other re-sets you can do for mileage while you're in there.

 

[Fless]

There is an alcohol content sensor that is finicky. Find someone with the right scan tool to do a re-calibration. There are a couple other re-sets you can do for mileage while you're in there.

Should be a "virtual" alcohol sensor on a 2008; no physical sensor. Alcohol content is re-settable using a Tech 2, but don't do that if your ethanol content is over 10% or so.

 

[alpha_omega]

He is recommending putting a mix of 87or 89 and e85 in at each fill-up. If you get the mix right they run well and the mileage is good.

I disagree that they run fine on 87. They run ok and it won’t hurt. I feel the performance on it is subpar and prefer 89 or E85 in my 2013. If you feel it runs fine then go with it.

Is your 2013 a 5.3l? If it’s the 6.0 or 6.2l that will make a difference in whether or not it runs fine on 87.

For E85 I think i get better gas mileage in the fall/winter but i need to test it as I just got this truck last year.

-When was the last time you changed out your fuel filter? Or did the 2008’s have them built into the tank/pump?

-Have you checked/cleaned the air filter, cabin air filter, radiator/condenser fins, Mass air flow (MAF) sensor?

-Are your radiator baffles in good shape and are your skid plates installed?

 

[George B]

Is your 2013 a 5.3l? If it’s the 6.0 or 6.2l that will make a difference in whether or not it runs fine on 87.


-When was the last time you changed out your fuel filter? Or did the 2008’s have them built into the tank/pump?

-Have you checked/cleaned the air filter, cabin air filter, radiator/condenser fins, Mass air flow (MAF) sensor?

-Are your radiator baffles in good shape and are your skid plates installed?

My 2013 is a 5.3 FLEX motor.

 

[bigdog9191999]

first off i would say that your results are in the normal range.

it will take a little for it to come back around to normal after having run it as it needs to "flush" it all back out.


on average if your not saving over 20% then it is just not worth the hassle unless your using it for performance, and most stock vehicles just dont NEED it, or can make best use of it.


here is the skinny on it. on the average driven vehicle it is usually just not worth it. dont mean it is better/worse just not mathematically worth it. the benefit is high performance stuff that takes premium or above, and the results are almost magical in a boosted vehicle ( that has been tuned correctly) as most vehicles that are boosted require premium or greater, and e85 is like running a mix of race gas and alcohol (because it is a form of it) the cooling properties of alcohol are awesome and to a point you can add more boost by simply adding more fuel. which means more power. and when prem is 1/3 more than reg and race fuel 5-7$ a gallon running e85 is dirt cheap and street legal. it just requires more of it, 20% in a stock type setup and up to about 40-50% more in a very high performance setup.

 

[CaptainAmerica1]

And E85 is just so much fun!!