Thread: Horrible gas mileage for my 06 GXP

OK so new update...


Just filled up today and after the recent changes since the last tank (correct tire pressure, 91 octane, and easy driving with the occasional first gear pull, the display said my tank averaged 15.1mpg. THis was a huge improvement from the last tank at 13.6. So the car read 15.1mpg and the distance from the last reset was 257miles. It said I had 39 miles left in the tank.

I put in a little over 16 gallons, then did the math to see what my true mpg was. I came up with 15.63mpg for this tank. So the display is off as I figured. Either way, I still increased my mpg about 1.5 miles. Not great but an improvement.

Next will be the intake and maybe exhaust to help. Yes a tune as well. Still disappointed, but what can you do with the DOD and it being a V8?

That's still crazy. Seems kinda low All I have is a CAI and basic tune up stuff and I average 19.2 over the last two weeks. I do run 93 octane but it shouldn't make that huge of a difference. Have u pulled ur plugs to check gaps and all

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marines...is yours a GTP or GXP?

It is not uncommon for the 5.3 V8's to do horrible in the city. it's like driving around a half ton truck. it ain't gonna do good til you get it rolling. Most i have EVER got in the city was 19mpg (usually around 15mpg) and most highway was just right at 30mpg. I use Royal Purple oils, keep tires inflated, have a Hogan 3" Catless DP and full 3" into dual 3" catback, CAI...untuned...

My GXP has been averaging 19.5-20.5 for a month now and I can get it to 22 being really nice to it on the highway. I drive 70%highway 30%city

Mines a gxp.

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i can do about 19 city if i drive like an old lady...really carefully...

but 35 highway? man...you using jet assisted packs on the decklid running downhill or something? that's nuts...

I'll take a picture of my DIC in the morning. I reset it after I got back from Thanksgiving. And all I do around here is city traffic on base. Higest speed I go during week is 35 and that's if there's no traffic

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Thought if humor y'all

Number miles driven since last oil change
uploadfromtaptalk1354721948661.jpg

This is avg speed since last oil change
uploadfromtaptalk1354721960608.jpg

Avg fuel economy since last oil change
uploadfromtaptalk1354721974390.jpg


I reset my trip A and everything every time I change oil

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my stocker only avergaes 17 now

if your avg speed is only 25 mph, likely thats why your thinking you mpg are low. thats pretty much all town driving.

in my 98 regal, if i light foot it, and i mean light foot on the gas, i can pull 18 mpg in town. as soon as i start doing faster starts from red lights and stop signs it will drop to 14-16 real fast.

Originally Posted by marines542

Thought if humor y'all

Number miles driven since last oil change
uploadfromtaptalk1354721948661.jpg

This is avg speed since last oil change
uploadfromtaptalk1354721960608.jpg

Avg fuel economy since last oil change
uploadfromtaptalk1354721974390.jpg


I reset my trip A and everything every time I change oil

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I dislike you

Originally Posted by scottydoggs

if your avg speed is only 25 mph, likely thats why your thinking you mpg are low. thats pretty much all town driving.

in my 98 regal, if i light foot it, and i mean light foot on the gas, i can pull 18 mpg in town. as soon as i start doing faster starts from red lights and stop signs it will drop to 14-16 real fast.

No I'm not worried about bad gas mileage. I actually seem to average quite a bit higher than most gxp's dunno why. But everyone else say they get like 15 city where as I get close to 20

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Originally Posted by marines542

That's still crazy. Seems kinda low All I have is a CAI and basic tune up stuff and I average 19.2 over the last two weeks. I do run 93 octane but it shouldn't make that huge of a difference. Have u pulled ur plugs to check gaps and all

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No I have not but this is my next step. I have done a bit more highway driving this tank and still only managed high 16s

Originally Posted by marines542

Thought if humor y'all

Number miles driven since last oil change
uploadfromtaptalk1354721948661.jpg

This is avg speed since last oil change
uploadfromtaptalk1354721960608.jpg

Avg fuel economy since last oil change
uploadfromtaptalk1354721974390.jpg


I reset my trip A and everything every time I change oil

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How many miles on your car?

I've got just over 46000 miles. I take good car of it. Replaced the plugs, wires, CAI installed, run 93 octane, synthetic oil, tranny pan drop and shift kit installed, and don't always drive like the cops are chasing me

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We get 24-25 on the highway if we are lucky

Dang I'll consider myself lucky then

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yeah I am still not anywhere near where all of you are. I have to check my plugs and it may be time for tune up

Im bumping this old thread...

So since 12/12, a lot has happened. Only about 5,000 more miles on the car since this thread was started, but more recently I had a lot of work done to the car. Plugs (2 were bad), wires, New tires, wheel bearings, engine mounts, a transmission service with new fluid and filter and a complete coolant flush. I also moved back to Pittsburgh from Arizona where I have been living the last 4 years and where the car was from.

I also now have access to awesome 93 octane as opposed to only 91 octane. I have been trying to baby the car since we have been back but with the winter, the car sitting for days on end while I drive my wifes land rover, the car running for 5 minutes in the mornings to warm up when I do drive it, and just to cold in general....I cannot get better than 15mpg. Now I know all the mentioned factors play a big part in this not to mention PA has hills and bends while Arizona was just flat for miles and miles.

I just had hoped that with the maintenance recently completed along with the better fuel, I would have averaged higher mileage. So...I just purchased the Diablosport Intune I1000 programmer to maybe help by shutting off the DOD and also for me to play with the factory tune. We will see.

My average is like 19.5.
Mixed Highway and City. I don't baby it, but I don't beat on it either. 120k miles on it too.