03 Z-oh-6

I just picked up an 04 z06 with with 7,300 miles, bone stock, very clean. I filled up the tank right after I bought it, reset all the fuel DIC's, and I noticed the gas mileage wasn't up to par with my prior 02 Z. The big test is when I took it on the freeway, I reset the average miles per gallon DIC and it only got up to about 22mpg on the freeway. I drove the same distance with my prior 02 Z everday, and it always climbed up to ~29 MPG. City driving in the 04 is only around 12 MPG. The car has obviously been sitting more than driven with only 7K miles in 3+ years. Car runs great, no codes. Do you think I need a tune?

UPDATE: For those struggling with gas mileage like I was, GET A TUNE!!! I just had my car tuned by Charlie(RPM Motors, A&A Corvette), and it made a world of difference with gas mileage. On the 50 mile highway ride back home from the tune, I reset the DIC. Before the tune, I got ~27 MPG on the highway. I hit 32.4 MPG on the way home! Also, in the city I was averaging ~13 MPG, I now average ~17 MPG. It's not your MAF, bad oxygen sensors, etc. Charlie said my fueling was way off. It blows my mind how such a beast of a V 8 could do so well.

Z28TOZO6

Any codes? check the o2 sensors?

03 Z-oh-6

No check engine light. If the o2 sensors were bad, wouldn't it throw a code?

GONZZO

Congrats on the new Z, Have you manually checked the mpg to see if the computer reading is incorrect.

Good Luck

froggy47

Maybe someone did a bad tune on it. Most tunes will improve mileage a bit.

03 Z-oh-6

I guess the stock tune is bad then.

CH.CRAFT

I HAD A 01 Z06, AND NOW HAVE A 04 Z06 W/6800 MILES. I BOUGHT BOTH NEW AND THE GAS MILEAGE IS VERY NEAR THE SAME AS FAR AS I CAN TELL.

hotwheels57

Have you checked the obvious? Air cleaner, change oil (viscosity to heavy), change manufacturer of fuel, air pressure in tires @ 30# psi, lift you right foot...

Ryan L

Sort of a side comment, but why trade the 02 for the 04? You had a strong 02 there making great power with only a tune.

pb24dagrk

It was out of warranty and he was having lots of issues with it where it was ruining his ability to enjoy the car every day or something like that

03 Z-oh-6

I had to have the bumper re-painted on the 02, they royally screwed up, had to re-paint it again. The ended up having to re-pain the fenders to get it to match. When they put the car back together, the panels didn't line up good. They just did an overall ****ty job. I just didn't feel the same interest in the car. Plus, I got a steal on the 04, it only has 7,300 miles, excellent condition, GMPP warranty through 08(with the option to extend), early warning lo-jack....all for 34.5K. Blue book on this car is easily 41K.

Side note, my gas mileage seems to better getting better. I'm changing the oil today(Mobil 1 10w30).

Ryan L

Tact

Just out of curiosity, what does changing to 10w30 do for gas mileage? I'm changing my oil and filter today and if it will benifit I'll do the same. Temps today near 97. and here in the south it's not going to get any better.

03 Z-oh-6

I don't think it affects gas mileage. The main reason for switching to 10w30 is because it's hot here in Southern CA. It's a bit better than 5w30 in the heat. I can run 10w30 year round because it never drops below 0 degrees around here.

Tact

I just changed the oil and filter today using Mobil1 10w30 and a Mobil 1 filter. AutoZone has a sale running now and I got all 7 quarts and filter for $43, including tax. The Mobil 1 filter alone usually runs $10.

2TONE82

12 MPG in town and 22 Hwy...somun's up. I get 16 ~ 17 with my '04 in town with my right foot planted firmly to the floor between lights...don't get me wrong; I don't do that often but I am amazed at how the gas mileage seems to get better the more aggressive I drive the car...who knows, damn thing amazes me all the time. As a point of reference, my Z06/Z16 has just over 20K miles, is bone stock and gets 18 or so in town (sane driving) and I've seen 29+ on a hwy run...can't seem to break that 30 MPG barrier!

ShadowLight

When I'm driving like a jerk (aka having fun) that's about right!

03 Z-oh-6

Update in the first post.

Z28TOZO6

I had headers put on in April, and my mileage went to $h!t, like 12 miles per gallon. I had it tuned and, while not as good as it was bone stock, I am getting 20 around town, with let's call it "spirited" driving.

Usually upsetting the stock headers and intake configuration will kill the gas mileage, but I guess it can go to hell stock. The computer is supposed to read the 02 sensors and adjust accordingly. I would imagine that if the fuel management system erred it would be to the rich side to prevent detonation, causing poor mileage.

I read recently that 02 sensors are pretty bullet proof and get changed more often than necessary.

Ryan L

So what are your new HP numbers, mangsicle?