Drove round trip from Dallas to Austin and back yesterday to watch my son and his UT-Austin club college baseball team play a double-header against U of Kansas (won both games and he played well, thanks for asking). Total trip was 460 miles, and I averaged 71 mph. At that speed, I got 25 mpg.

My C5 automatic is set up as follows: L/T headers, mild cam, AFR 210 heads, CAI. 405 rwhp/400 rw ft/lbs.

Does 25 mpg sound about right (given the speed at which I was travelling)? A bit too low? I didn't hammer the throttle, ever, and drove 230 miles non-stop (without even passing a traffic light) each direction for the entire trip (gassed up in Austin about a half mile from the baseball stadium). I enjoyed a slight tail wind on the south-bound leg, the wind turned calm on the return leg, and I drove in temperatures ranging between the upper 40's down to the low 30's. So wind and temerpature should not have been negative factors.

Just curious.

I have read where others say their C5s have achieved mpg in the upper 20's to low 30's, but it was unclear the speeds at which they were travelling when they achieved their reported mpg. [For full disclosure, in order to average 71 mph, I had to actually drive at or above 80 for much of the time (yep, stretches of I-35 have a posted 75 mph, and my V1 pulled sentry duty the whole way).]

I'm getting ready to install 3.42 gears and a stall converter. I want to give my tuner (True Street in McKinney, TX) this feedback so he can address identified issues, if any, while he is tuning my transmission.

 

This is all I seem to be getting lately.
When she was younger she could regularly hit 28 - 30 per tank but the last 2 years have been 23 - 25 on the same route at the same speeds.

 

Sounds about the same as my bolt-on Z06. Have to do 60-65 to get those 28-30mpg figures.

 

I seemed to lose about 2-3 mpg in the past few years as well, my guess is the fuel blends.

 

I suspected as much.

To me, crawling cross-country on an interstate at 60 mph is kinda contrary to the purpose of owning a Vette. I mean, what's the fun in that? If observing the scenery was my objective, I would ride in an SUV and poke along in the right-hand lane behind the 18 wheelers.

Besides, Vettes aren't particularly comfortable to drive over long distances. My 64-year-old legs cramped up several times on the return trip, and there just aren't too many ways to stretch out. So extending that misery by poking along isn't my bag.

The Lizzard

 

I get a bit closer to 30 or so out on the highway like that.

 

I get around 30 mpg in my stock 2003 A4 on highway trips. I was talking to some knowledgeable folks about putting LT headers and a cam on my Corvette. They said the headers would help with MPG, but that a cam could lessen MPG. Just a thought.

 

what size is your cam? im surprised it PUTS along that well with the stock stall speed.

 

Comp cams 224-230.

I know about as much about cam technologies as I do about molecular physics (I can spell it but not much more).

 

I typically get around the 30 mark, stock. But I have noticed a drop off this winter some, it has to be the fuel blend causing it.

 

I calculated 24mpg (computer showed 27) all highway from Dallas to Arkansas, and thats with 470+ whp in my Z06

 

my 01 Vette/stock/auto. gets 28 at 70mph in warm weather. mpg goes down in cold weather, and with ethanol in the gas it goes even lower in the cold.

 

See that's what I'm thinking as well. We have ethanol and my mpg goes down in the winter. Way down.

 

MPG always goes down in winter time. Over the summer (according to the DIC, which is never 100% accurate) I was getting 34MPG going 75-80 down the highway. Now I'm barely hitting 30's.

 

I wonder why fuel efficiency decreases in colder temperature. It would seem that the opposite would occur, since colder weather would mean denser air, which would mean more efficient combustion, more power and thus less need to mash on the go pedal. Curious.

I never, never, ever rely on trip computers to calculate mpg. Miles driven divided by gallons used is the ONLY way to accurately calculate that measure of fuel efficiency.

Average miles per hour, as calculated on our trip computers, is also fatally flawed. Miles driven divided by hours driven is the only meaningful calculation. (Duh!)

 

I lost about 4 mpg in my 4 runner 2-3 mpg in the vet.Burning E-gas means burning and wasting crops
.Burning and wasting money.
FRED

 

For an A4, yes, that sounds reasonable. Mine is an auto also, and I get 25-27 mpg with it at that speed - no performance mods other than a Blackwing.

 

I get just over 30 mpg on the highway with my 2000 A4. I'm sure that will change with age and additional miles.

 

Thanks, VJ.

I am getting a sense that the "I get 30" crowd is either coasting downhill with the engine shut off or putting along at 55 mph in the slow lane, or perhaps both, and in any event relying on their (notoriously optimistic) trip computer data rather than calculating the real mpg.

I always calculate (in my head) the mpg I got from each and every tankfull of gas. Why? Because a sudden decline in mpg is an early warning signal of trouble, and the earlier discovered, the less onerous the remedy.

Following that train of thought, though, I need to have a reasonable starting point. Sad to say but I rarely drive my Vette exclusively on the highway for sufficient miles to record/monitor highway fuel efficiency. So when I do, I want to have a benchmark against which to measure my results.

Sounds like 25 to 27 mpg (when averaging over 70 mph) is that benchmark.

Regards,

The Lizzard

 

I'm getting about 25ish on the highway, but way below 20 in the city. I can't figure out if I can improve that. Any way I can do this by shutting down some cylinders?