Gas Mileage

[viet69]

The best I have gotten is 30.5 and 654 miles on one tank full.The second best is 30.1 and 613 miles to the tank. I use the computer and do it by pencil and paper as well. Mine is a paddle shift 08 coupe.

 

[gmjunkie]

Hey, Junkie, you are running a 6sp -- right? My automatic will not turn under 2,000rpm at 80mph.

Yeah,Both my C5's are 6 sp, the 01 Z06 don't do near as good as the 03 Z-51!!The best I've ever gotten with the Z06 is around 26-28.5,Probly the way I drive it!!

 

[jhecox]

We took both C6's to FunFest, a little over a 1,000 miles with going 30 miles each way back and forth to the hotel. I reset the Wife's to see what she would get (see drives harder than I do ). Both cars will get 30 - 31 mpg on a flat and level interstate at 80 mph. She averaged 27.8 mpg on the trip with her A6.

Hecox

 

[bucket]

my first fill up with my stock LT1 92 auto was 7 mpg.......i guess my driving style was a bit agressive

and later on a road trip to nevada....23 mpg....flowing nicely with traffic...lol


Maybe you guys should buy a prius

 

[Cruzen]

Tire diameter and rear end ratio will play a part. You may have the performance ratio with low profile tires and are comparing it to others who have the standard ratio with stock profile tires.

Except for the sound, a change in exhaust system is not going to matter at the RPM's you are running. They only matter when you get in the upper RPM's. In fact in the 70's when I participated in several dyno and in car tests of exhaust systems on Chevy small blocks used in short track racing. We found that there was little gain in performance between the stock 1970 LT1 camaro exhaust and a less restrictive large tube exhaust on a small block under 4000RPM. In addition, when we tested headers and went from a 1 5/8 header tube to a 1 7/8" header tube we experienced a significant reduction in HP and torque below 5000rpm. These tests were run using a near stock 1970 LT1 (350) and a modified cross ram 302 out of a 1969 Z-28.

If you have done anything to reduce the torque of your engine, such changes will impact gas mileage.

My 1994 Vette roadster with LT-1, automatic, and 100K miles on the odometer with stock dia Nito tires at 35PSI and 3:42 rear end gets 25-26MPG on highway holding around 75MPH with air on. This drops down to 23-24 when I go up and down the mountains to Flagstaff and attempt to maintain 75MPH.

My stock C5 98 Roadster with 40K miles, automatic and performance axle ratio, Firestone run flats at 37PSI, gets 27-28 mpg with top up and air running on the reasonably flat roads between Scottsdale, AZ and Los Angeles CA. That drops down to 26-27 when I run up and down the 5000 ft mountains going from Scottsdale to Flagstaff.

The C4 gets 19-19.5 around town and the C5 gets 20-21 around town.

 

[darkstar]

Tire diameter and rear end ratio will play a part. You may have the performance ratio with low profile tires and are comparing it to others who have the standard ratio with stock profile tires.

Except for the sound, a change in exhaust system is not going to matter at the RPM's you are running. They only matter when you get in the upper RPM's. In fact in the 70's when I participated in several dyno and in car tests of exhaust systems on Chevy small blocks used in short track racing. We found that there was little gain in performance between the stock 1970 LT1 camaro exhaust and a less restrictive large tube exhaust on a small block under 4000RPM. In addition, when we tested headers and went from a 1 5/8 header tube to a 1 7/8" header tube we experienced a significant reduction in HP and torque below 5000rpm. These tests were run using a near stock 1970 LT1 (350) and a modified cross ram 302 out of a 1969 Z-28.

If you have done anything to reduce the torque of your engine, such changes will impact gas mileage.

My 1994 Vette roadster with LT-1, automatic, and 100K miles on the odometer with stock dia Nito tires at 35PSI and 3:42 rear end gets 25-26MPG on highway holding around 75MPH with air on. This drops down to 23-24 when I go up and down the mountains to Flagstaff and attempt to maintain 75MPH.

My stock C5 98 Roadster with 40K miles, automatic and performance axle ratio, Firestone run flats at 37PSI, gets 27-28 mpg with top up and air running on the reasonably flat roads between Scottsdale, AZ and Los Angeles CA. That drops down to 26-27 when I run up and down the 5000 ft mountains going from Scottsdale to Flagstaff.

The C4 gets 19-19.5 around town and the C5 gets 20-21 around town.

You make me wonder if I didn't inhibit my gas mileage somewhat by installing a Corsa Sport exhausts system and a Callaway cold air induction system.
My baby is equipped with the MN6 option (3:42 axle & GU6 shorrt throw tranny) and the GY Eagle F-1 Supercar tires.

 

[DDLS3]

Interesting.....my 08 Z51 mn6 never got better than 25 mpg on a trip to Maine a couple of weeks ago. That was a 3000+ mile round trip, same trip with my 02 got 30 mpg. Not nearly as much fun though with less horsepower though.

 

[darkstar]

Interesting.....my 08 Z51 mn6 never got better than 25 mpg on a trip to Maine a couple of weeks ago. That was a 3000+ mile round trip, same trip with my 02 got 30 mpg. Not nearly as much fun though with less horsepower though.

A least I am not the only one. As you said "not nearly as fun though".

 

[Cruzen]

You make me wonder if I didn't inhibit my gas mileage somewhat by installing a Corsa Sport exhausts system and a Callaway cold air induction system.
My baby is equipped with the MN6 option (3:42 axle & GU6 shorrt throw tranny) and the GY Eagle F-1 Supercar tires.

That may be. Take a look at the performance curves provided by the manufactures of your upgrades and pay attention to the lower RPM range. Those increases in performance they advertise usually happen in the upper RPM range. If you seldom use those upper RPM ranges then you wasted your money. On the highway in overdrive your engine is running at or below 1800RPM in sixth gear. What do their performance curves show for RPM ranges below 1800?

In some cases, not all, at these lower RPM ranges such performance upgrades as you described will actually put out less than the stock systems. That is why I usualy focus on the impact upgrades will have on the RPM range I use on a daily basis not that occassional sprint, unless that occassional sprint is more important to you than daily driveability.

 

[darkstar]

That may be. Take a look at the performance curves provided by the manufactures of your upgrades and pay attention to the lower RPM range. Those increases in performance they advertise usually happen in the upper RPM range. If you seldom use those upper RPM ranges then you wasted your money. On the highway in overdrive your engine is running at or below 1800RPM in sixth gear. What do their performance curves show for RPM ranges below 1800?

In some cases, not all, at these lower RPM ranges such performance upgrades as you described will actually put out less than the stock systems. That is why I usualy focus on the impact upgrades will have on the RPM range I use on a daily basis not that occassional sprint, unless that occassional sprint is more important to you than daily driveability.

Well you got me. I was under the impression that improving the breathability of the engine started in the low RPM range affecting both hp and torque to a small degree depending on the modification.
I will have to do some calling around and see what RPM range I have actually had an effect on. As I said I thought it was low end and up unlike a cam change or a supercharger.
Thanks for the info.

 

[Blue260]

I have an 05 Coupe with the Z51 Package. I just put on Corsa Exhaust and kept my original "H" pipe. I also installed a Air-Aid Cold Air Intake.
We just got back from the Effingham show and I only got 25 MPG. I would have thought it would have done better. I have been using 93 oc. or better gas.
Any thoughts or things I might possibly do to help get better MPG.

If its any comfort, the most I ever got from my 08' with similar mods is 28 and that was from SC to VIR in Va.

I average about 18.5 to 19 with consistency. My round trip drive to work is about 30 miles and I try to make it an enjoyable ride before I reach prison (I mean work)!

If I wanted to drive it like a senior (which I am), I would have bought a Honda.
Oh, how I'd like to revisit 1969 and 70' with my current ride!:cool

 

[cadguymark]

gas mileage will decrease as the temp gets colder, maybe that is why you got 25mpg

I took two extended trips out west this summer, mpg ranged from a low of just under 28 (on my way home and driving well above speed limit) to over 35 (yep, 35mpg) cruizing through mountains at 50-55, have LS2 with 6 spd

contrary to what people believe, gas mileage decreases as you go faster, all else remaining the same, there is no getting around the fact that air resistance in particular and rolling resistance in general increases dramatically the faster you go (non-linearly)

 

[napacruzerC5]

Don't forget that usually for a long trip even when driving "legal" speed you are also probably near or over the cargo weight rating for the vette. During my last long trip I figure between my wife and I, our two Dachshunds, travel kennel, cooler, lugguage for 10-days and various odds and ends probably close to 700 pounds. Starting off each trip with a full tank and not letting it get lower than 1/3rd tank also adds the weight which all have an effect on gas mileage. Now who's going to look through their owner's manual to see what our vettes are rated for cargo/passenger carrying weight. And I bet during the holidays our vettes could put Santa's sleigh to shame