Pontiac G8 2008-2010 - Gas Miliage on GT

I am in the market of trying to find a daily driver that will get me better MPG from my supercharged Tahoe and my 800 RWHP Trans AM.

I have always loved these cars and I am trying to see what the real world MPG is on these cars.

My truck gets 13 mpg and the trans am gets 9 to 10 mpg in town. So I am guessing it has to get better than these.

Thanks.

mine varies from 19-22mpg and i do 80mph all the time..lol

mine varies from 19-22mpg and i do 80mph all the time..lol

I hope they get better than that running 70mph. I am picking up a new to me GT this weekend and I drive 120 miles daily!
Over on the G8 board guys claim mid 20 mpgs

Took a friend to the Air Port yesterday. 2 hour round trip and reset just when I left. Got home and averaged 26.2 with an average speed of 67 MPH for the trip. That's with my mods in sig. Not bad for a 4k lb family car that runs 12.5s.
Tate

Thanks. Thats exactly what I wanted to hear.

Know I guess the decision is, Grey or Stryker Blue.

The goal of the car is to make a wicked cool daily that I can take on some amazing road trips in.

I average about 19, but I beat on my car like crazy.

Yeah, I am in the 19-21 range with 60% highway, 40% city.

I drive 50 miles a day round trip. Usually 50/50 highway/city. I've been getting 18.0-18.5 without trying. Hope this helps.....

I've been averaging 16-18 with mostly around town (spirited) driving. On highway trips I was getting 25+ before my CAI and tune. Hoping I gained a little there, but I haven't had a chance to check it yet. A tune makes all the difference in the world on how these cars drive though.

19-20 mpg in mixed driving. Highway I usually get 26 mpg on 70mph cruise control. Mods in sig. You don't have to lose mileage with a cam setup if the combo is right and tune dialed in.

Mileage usually looks like this with 50/50 city/hwy... for comparison I used to get 18-19 mpg on the same circuit in factory trim.

http://i610.photobucket.com/albums/tt181/johnbell2/gas-mileage-with-cam-setup.jpg

19-20 mpg in mixed driving. Highway I usually get 26 mpg on 70mph cruise control. Mods in sig. You don't have to lose mileage with a cam setup if the combo is right and tune dialed in.


Very few mods will make you lose gas mileage if you can resist the temptation to drive faster. If you can't resist, gas mileage could suffer quite a bit ;)

Very few mods will make you lose gas mileage if you can resist the temptation to drive faster. If you can't resist, gas mileage could suffer quite a bit ;)

I hear that! I've seen my share of 14-15 mpg tanks :D

I get about 16-18 MPG and I drive 90% rural highway (60 mph) and rural Istate (78 mph). Kind of hilly.

Stock I got about 20-21 driving around.

19-20 mpg in mixed driving. Highway I usually get 26 mpg on 70mph cruise control. Mods in sig. You don't have to lose mileage with a cam setup if the combo is right and tune dialed in.

Mileage usually looks like this with 50/50 city/hwy... for comparison I used to get 18-19 mpg on the same circuit in factory trim.

http://i610.photobucket.com/albums/tt181/johnbell2/gas-mileage-with-cam-setup.jpg

What are the specs on your cam?

mine varies from 19-22mpg and i do 80mph all the time..lol

I got a nitrous kit with your name all over it

What are the specs on your cam?

The usual - 218/230 0.600/0.600 115+3 - nothing fancy.

I just got 24mpg on a highway trip with the wife, 2 year old and 3 month old, and trunk full of luggage and stuff in the interior too doing around 70mph.

Oh and if you get Styker Blue, Ill be so jealous!!! These cars look awesome in that colour.

You probably already know, but the L76 in the G8 GT has AFM (Active Fuel Management). So at highway cruising nspeeds, (65MPH and less I believe) it will shut off 4 cylinders.

The car is rated at about 15 city/24 highway by most reviews. I have a friend who has one, he swears up and down the aisle that he gets 27MPG going 70MPH in stock form.

The usual - 218/230 0.600/0.600 115+3 - nothing fancy.

The wide lsa is a big reason for such decent mileage for a cammed vehicle. Wouldnt happen to have a sound clip would you? Thats a good cam for a maggy :D

The wide lsa is a big reason for such decent mileage for a cammed vehicle. Wouldnt happen to have a sound clip would you? Thats a good cam for a maggy :D

Dyno sheet, the bottom line is stock tune with CAI installed. Full stock baseline was 294 rwhp / 313 rwtq:

http://i610.photobucket.com/albums/tt181/johnbell2/JB-G8-GT.jpg

Sound clip of cold start:

http://www.youtube.com/watch?v=XxsX96BjBdY

This car is my daily driver. Mods resulted in +113 rwhp / +77 rwtq from stock baseline. Worst case I get the same mileage as I did stock under normal driving conditions, most of the time I get +1 mpg vs. factory. We have lots of hills in Austin, AFM would cut out so much it was little help in the mileage department. Between that and the reliability concerns it's not missed.

Dyno sheet, the bottom line is stock tune with CAI installed. Full stock baseline was 294 rwhp / 313 rwtq:

A stock G8 GT with 361HP only puts down 294RWHP? That's about the same as a stock LS1.

This is good news for my race against one of my friends who owns a G8 Gt!

A stock G8 GT with 361HP only puts down 294RWHP? That's about the same as a stock LS1.

This is good news for my race against one of my friends who owns a G8 Gt!

Mine was an 09.5 - extra pup cats so factory SAE was 355 not 361.

The 6L80E eats up ~60 hp. My dyno numbers were in line with that.

with my mods i averaged 28 at 72mph. at 45 i averaged 41mpgs

with my mods i averaged 28 at 72mph. at 45 i averaged 41mpgs

41 MPG in a 6.0 liter 4,100 lb car? Is that what the computer is telling you? Or did you do the math yourself...miles driven divided by gallons it takes to fill up?

thats what the computer said. remember with the dod on. it runs on 4 cylinders. just under like 10% throttle

Yeah... I don't believe that. The computer tends to not be good at calculating MPG over short terms. The accuracy is debatable even over the long term.

The DIC has always been in lock step with my hand calcs. Always. I check it at every fill-up. Hasn't deviated in over two years of ownership. You can play tricks with it in the first 10 miles or so after fill-up but it always settles down to reality after that. I'd never show a DIC reading that went through less than an eighth of a tank. That's just funnin'.

People always say they got "the freak" (never mind that our engines are SAE certified but let's not ruin people's fish stories). I guess I got "the freak" when it comes to DIC accuracy on gas mileage ;)

in stock trim it was nothing for me to get 29-33mg over 400 mile trip to texas or back since the tune its went down to 23-25 i'm gonna check a few things when i get home cause what i'm getting now is not good

Even when I was extremely light footed and stock 23-24 is the best reliable number I ever saw. Driving from west to east on a down sloping part of the country I got in the high 20's one time. The GXP gears probably don't help.

After a 360 mile trip mine got 24mpg. This is an actual calculated mpg, not using what the dash showed me. I am happy.

Here is mine. It's a 100% stock G8 GT

http://www.mpgtune.com/fillupHistory.php?carId=4837