C4 Mileage... Revisited

[C4Tom]

I know, I know... been discussed many times.

I went to Kings Island in Cincy last Friday. I filled up the Vette, reset the fuel stats and headed southeast down I-74. By the time I arrived, the 'avg mpg' was 30.8 mpg!!!

Heading home I got on the interstate and reset the stats once again. By the time I got home the average was only 26.6 mpg. :cry

I suppose I was a bit heavier on the pedal heading home. I was just amazed to pull almost 31 mpg on the way down. I know that the avg has many factors and can differ greatly unless it has been taking the readings for many miles. (I've been told that Cincinnati sucks... so maybe the Vette was being pulled towards Cincy causing the high mileage )

Just letting ya know.

 

[DAVZKAR]

Is that a stick or auto, what gear ratio? The best I get is 26 on mostly highway. Mine has 2:59 gears with auto trans.

 

[C4Tom]

Sorry, should have stated the specs.

LT1, auto, 2.59 gear.

If I stay out of it... driving around normally(city & highway), I get about 24 mpg average.

 

[DAVZKAR]

If I find the time I am going to the performance ratio, 3:07.

 

[Vettefan87]

I want to get 3.23's, whenever I can find the differential, and the gears.

 

[WhalePirot]

Are those numbers from the ECM or computed like the old days? Back when mine worked, I wondered if they were accurate.

 

[Vettefan87]

I have found that mine is pretty accurate if you reset it after each time you fill up.

 

[Txbobcat]

I just finished a 2000 mile trip in my 92 Conveert with 6 speed and pulled 29.9 on the whole trip normally 72 mph some traffic and some heavy rains a few hours with the top up and ac on. I was very hppy with it

 

[jmccloud]

Mileage

My '95 Auto (2.5? gears) will do 30mpg on a trip, but more like 26 if the A/C is on. I live 10 miles outside of 'town' and get 20+/- 2 mpg depending on how much traffic is in town and whether the A/C is on. Also, extended driving (more than 12 miles or so) in one trip really improve the mileage. Short hops (5-10 miles then stop for an hour) really knock the mileage down.
The computer's mileage calculation is within 5% of a 'manual' calculation and the odometer is within 2% of roadway markings. Some miles on the interstate are a lot shorter than others but they average out over 20+ miles.

 

[Hrtbeat1]

My '90 2.59 auto used to get 26-29, both displayed and calculated. I used to have a 57 mile drive to work daily (50 of it interstate) so I was always keeping track of the mileage.


I swapped out the 2.59 with a D44 and 3.45 a while back. The first real road trip I took was going to BG for Cruisefest. I averaged 24.7 MPG for the 552 miles there, avg speed for the whole trip was 63.7 MPH (with an hour slowdown in Nashville!) On the way back I took a different route 610 miles avg speed 74.3, avg MPG 22.8. I could have gotten better if I would have kept t to around 70-75. I'll give up the little change in MPG for the acceleration I get with the 3.45's though.

 

[C4Tom]

Are those numbers from the ECM or computed like the old days? Back when mine worked, I wondered if they were accurate.

This was the reading from the ECM. I have verified it before and it is real close to being right on.

Note: I had the air off going there and on during the trip home. Didn't realize the big difference with A/C on. I had the cruise control set for 78 on the way down with A/C off and got nearly 31 mpg. Yet I had the CC set on 75 with A/C on and got 26 mpg going home.

Another thing I found when driving long distance, My car gets better mileage at different speeds. I've found that going 67 mph will increase mpg for short highway jaunts and speeds near 80 for long drives will give me better mpg.

 

[DJ's LT1]

My 96 auto has the 3:07 gear ratio and never gets above 25mpg. I guess this is still pretty good considering that the A/C is always on. It's ALWAYS HOT here in South Texas!!!!!

 

[SPANISHVETTS]

I guess that I should kiss Frankie’s back side for the job he did dialing in the 383. Thunder (auto with 3.08s) does 25+ MPG at 100 MPH with the AC blowing.
On the down side, in town or on short runs it drinks gas like a bigblock.

 

[cjs2]

Best I did was 28 + (2.59). Around town usually do between 18 - 20. Sure beats my SUV's (Suburban @ 10 - 12 MPG and Explorer 15 MPG) $2.25 a gallon for reg here!!!

 

[WhalePirot]

in town or on short runs it drinks gas like a bigblock.

Oh, gee. How thick is that soft gray metal in your right shoe?

I am interested in the mileage with the 406. My gut feeling is it's not too bad, but I have no long trips to calculate. With the ECM change, I lost my readout, which I watched quite a lot, as I do in my other cars.

I suspect that properly tuned, the aerodynamics dictate mileage more than the mods, underscored by Thunder's numbers. Also, those thottle changes and extra drain from A/C, take quite a toll from the steady state throttle position (as we see with the hybrid cars).

 

[John Robinson]

Milage

C4Tom I also have a 93 coupe LT1 auto with 2:59 gears. The best I have ever gotten is 25.5 cruising at 60MPH for 444 miles. My questions are how many miles do you have on your car and when was the last time you changed the plugs. Also have you changed the wires. My car has 76K on it and is still running the orginal wires and plugs.

 

[geekinavette]

I know, I know... been discussed many times.

I went to Kings Island in Cincy last Friday. I filled up the Vette, reset the fuel stats and headed southeast down I-74. By the time I arrived, the 'avg mpg' was 30.8 mpg!!!

Heading home I got on the interstate and reset the stats once again. By the time I got home the average was only 26.6 mpg. :cry

I suppose I was a bit heavier on the pedal heading home. I was just amazed to pull almost 31 mpg on the way down. I know that the avg has many factors and can differ greatly unless it has been taking the readings for many miles. (I've been told that Cincinnati sucks... so maybe the Vette was being pulled towards Cincy causing the high mileage )

Just letting ya know.

Downhill one way uphill the other? :L

Bill

 

[LT4man]

I get 30+ mpg at 75 mph. If I go slower, the mpg goes down. All has to do with where the torque curve is located. The cam decides that. LT1s have less aggressive cam than LT4s. Torque curve is different and peak torque is at a different point.

My around town mileage is much lower. I do have a tendency to use a lower gear and keep the rpms up. I like the sound of my exhaust. Small trade-off.

Save The Wave!

 

[C4Tom]

C4Tom I also have a 93 coupe LT1 auto with 2:59 gears. The best I have ever gotten is 25.5 cruising at 60MPH for 444 miles. My questions are how many miles do you have on your car and when was the last time you changed the plugs. Also have you changed the wires. My car has 76K on it and is still running the orginal wires and plugs.

Hey John,

My Vette just recently turned over 72K. I had the plugs and wires changed last summer. I also run a bottle of injector cleaner thru it every other month. You are probably due for a tune-up about now.

 

[John Robinson]

Plugs & Wires

Hey John,

My Vette just recently turned over 72K. I had the plugs and wires changed last summer. I also run a bottle of injector cleaner thru it every other month. You are probably due for a tune-up about now.

Tom

I think I will tackle that job next. I have not been able to do much work on my car because of health reasons. I have had the 3rd and 4th surgical procedures on my heart since May. Today I tackled fixing the Dimmer switch. As you know we are in a frigid time right now in Indiana. After successfully proving I can still work on my car I have started to plan the plugs, wires, Front rotors and brakes. But I may have to wait for a little warmer weather to work on those things.:J