C4 - What gas mileage to expect?

[robert kirk]

KOPBET.......... i have no idea how many miles were on the old o2 sensors, the car had 88 on it and they looked ori. when i first got it it would read 22 or 23 avg. after the tune, plugs, wires,opti,iac valve, icm,injectors, the avg droped to under 20. i posted on the forum and got several answers on what the problem could be. the o2 sensors seemed to be the common point. after putting in new ones the avg steadly rose and leveled off at about 24 avg. I drove the car hard last weekend to and from dallas and got excellent milage. there were places on the way home that i ran well above 100 for extended periods [60 miles at one point] and the instant milage never droped under 20 when leveled off. overall i was very pleased whith how well the lt1 preformed. robert

 

[KOPBET]

What does your instant MPG read while you're on the road? Have you reset your Average MPG to start at zero again? I apologize if this is a stupid question. Just trying to cover all possibilities.

Reads from 0 at drive off to high 40s at coast, otherwise it depends on workload obviously. Mostly in the low to mid 20s though. I think I was successful at resetting MPG to zero, at least I know I reset the trip odo and gas.

KOPBET.

 

[KOPBET]

Thanks to all who have replied so far.


KOPBET.

 

[KOPBET]

KOPBET.......... i have no idea how many miles were on the old o2 sensors, the car had 88 on it and they looked ori. when i first got it it would read 22 or 23 avg. after the tune, plugs, wires,opti,iac valve, icm,injectors, the avg droped to under 20. i posted on the forum and got several answers on what the problem could be. the o2 sensors seemed to be the common point. after putting in new ones the avg steadly rose and leveled off at about 24 avg. I drove the car hard last weekend to and from dallas and got excellent milage. there were places on the way home that i ran well above 100 for extended periods [60 miles at one point] and the instant milage never droped under 20 when leveled off. overall i was very pleased whith how well the lt1 preformed. robert

Robert, that's pretty amazing to get 20 at that speed. Are the O2s hard to get to? :eek

 

[jmccloud]

Sanity check

I'd get on a marked highway (Interstate) to get measured miles then check the odometer for 10 miles or so.
Then check speed (60 sec per mile at 60, etc.)
Don't mean to be insulting, but the C4's have a computer adjustable speedometer and odometer. If either of these is off, the mileage calculation will be off. Then you can get the actual mileage by dividing the now accurate odometer miles by the gallons put into the tank.
It's a lot cheaper to get the computer speed and odometer adjusted than to replace O2 sensors.
To replace them, the pipes need to be hot and a really strong wrench is needed. I use an air hammer socket (forgot the size) with a slot milled in the 1/2" drive opening (to fit the wire through) and still must strain a lot to pop the old one loose. They ain't cheap to buy either.
Check the easy to fix cheep stuff first.
John

 

[SPANISHVETTS]

9 city, 19 highway
To me stock is something that you roundup on a ranch, buy on Wall Street, or put in soup. It has nothing to do with the lump under the clamshell of my Vette.

I get crappy mileage, but I drive like a @#ole. Home to the track is 11 miles. 1mile out of the community, 4miles of 2lane farm road, and 6Miles of high-speed 4 lane. By the time I hit the good road I am so P´$$ at the bad drivers around me that I boot it and cover the last bit in about 3 Min. Also, this time of the year I never get into closed loop so that adds to the low mileage.

Over here we can drive faster than back in the USA. On the AutoPista (Turnpike) I run with the fast guys at +/-115MPH. At these speeds I am averaging 19.5 MPG. I would love to get better mileage on the road. The BMWs and P cars that are on the road with me do not get any better gas mileage than the Vette and their tanks aren’t as big, so at the end of the day I am usually ahead by about one gas stop.

I just filled up today. 22.5 Gal. $88. How would you guys feel if it cost you $4 per gallon for go juice.

When I started this reply it was not political, but things change. Let’s go kick some Ass. May God bless all Americans who stand in harms way, especially those who drive Vettes, including my son, who I hope flies better than he drives.

God bless America, to hell with MPG.

Sorry to hijack your thread, come visit my track and every thing will be alright.

 

[KOPBET]

9 city, 19 highway
To me stock is something that you roundup on a ranch, buy on Wall Street, or put in soup. It has nothing to do with the lump under the clamshell of my Vette.

I get crappy mileage, but I drive like a @#ole. Home to the track is 11 miles. 1mile out of the community, 4miles of 2lane farm road, and 6Miles of high-speed 4 lane. By the time I hit the good road I am so P´$$ at the bad drivers around me that I boot it and cover the last bit in about 3 Min. Also, this time of the year I never get into closed loop so that adds to the low mileage.

Over here we can drive faster than back in the USA. On the AutoPista (Turnpike) I run with the fast guys at +/-115MPH. At these speeds I am averaging 19.5 MPG. I would love to get better mileage on the road. The BMWs and P cars that are on the road with me do not get any better gas mileage than the Vette and their tanks aren’t as big, so at the end of the day I am usually ahead by about one gas stop.

I just filled up today. 22.5 Gal. $88. How would you guys feel if it cost you $4 per gallon for go juice.

When I started this reply it was not political, but things change. Let’s go kick some Ass. May God bless all Americans who stand in harms way, especially those who drive Vettes, including my son, who I hope flies better than he drives.

God bless America, to hell with MPG.

Sorry to hijack your thread, come visit my track and every thing will be alright.

Rant on brother! To me stock also is what I put into decent advice from people who know a lot more about this stuff than I do. I can also take it or leave it. I'm sorry you get screwed at the pump but I'm sure you can afford it. 115 on the Turner Turnpike will get me 30 days.

Wish I could come visit your track but my vette can't swim. It can fly though. Just hard to find gas stops along the way.

God bless America and your son.

KOPBET.

 

[KOPBET]

Re: Sanity check

I'd get on a marked highway (Interstate) to get measured miles then check the odometer for 10 miles or so.
Then check speed (60 sec per mile at 60, etc.)
Don't mean to be insulting, but the C4's have a computer adjustable speedometer and odometer. If either of these is off, the mileage calculation will be off. Then you can get the actual mileage by dividing the now accurate odometer miles by the gallons put into the tank.
It's a lot cheaper to get the computer speed and odometer adjusted than to replace O2 sensors.
To replace them, the pipes need to be hot and a really strong wrench is needed. I use an air hammer socket (forgot the size) with a slot milled in the 1/2" drive opening (to fit the wire through) and still must strain a lot to pop the old one loose. They ain't cheap to buy either.
Check the easy to fix cheep stuff first.
John

Your'e not insulting. However I did say in an earlier post that I have not yet calculated actual gas mileage. I was simply looking for MPGs from others who have a hell of a lot more seat time than I do so I would know what to expect from a first time C4 and, what might be wrong if mine is way out of whack.
Good advice about the easy stuff first; makes sense. Just need to know what that other, easy stuff is.
Thanks jmccloud.

KOPBET.

 

[Mad-Mic]

Kopbet,

are you resetting your trip guages after every refill? if so you won't get an accurate reading till after 100 miles. till then it'll very like your instant mpg.

my avg is

city 20 mpg with alot of hard romping
hwy 26-28 mpg

87 stock coupe auto 2.59 gear

 

[KOPBET]

Kopbet,

are you resetting your trip guages after every refill? if so you won't get an accurate reading till after 100 miles. till then it'll very like your instant mpg.

my avg is

city 20 mpg with alot of hard romping
hwy 26-28 mpg

87 stock coupe auto 2.59 gear

Actually, the dealer purchased from filled tank and reset. Drove 280 miles or so and filled again. This is just my second tank full. Avg. MPG has hovered around 13-13.5. Vettelt193 suggested in an earlier post disconnecting the battery for a few minutes to reset the 'puter. Did that tonight and then topped gas off. This for sure reset all the MPG stuff. MPG now has already hit 15 after just 10 miles of city driving and had not done that before. I'll have to keep an eye on after 100 or so.

I noticed your gears are 2.59. Mine are 3.07. I guess this could have a big impact on mpg?

Thanks,

KOPBET.

 

[Vettelt193]

If you don't have a heavy foot, the difference between 3.07 and the standard rear shouldn't be different in town. The biggest change is on the highway. Now, if you have a heavy foot.... whole different story

glad to hear the computer re-set seems to be working... fill us in with updates if you have time

 

[RedHookGal]

The first night I got the car, two weeks ago, I ran it out on the highway for about 150 miles. Averaging about 65 mph over that time, and running it up to 100+ a few times, I got 26mpg.

Since then it has been almost all NYC driving, and even here I am still getting 16mpg as of this morning.

All in all a very pleasant surprise - I never expected 16 in this town out of a Chev 350. My '87 Chev 10 pick-up with the throttle body injection only gets 13-14, and it has a 305 plant.

Kathy

 

[KOPBET]

Thanks to all.

Thanks to all that replied.

This car is not a daily driver so I will need to get more miles on it this weekend and see how it goes after a hundred or so miles. After only 26 miles on this tankfull, the avg. MPG is up to 16 and has never reached this level B4 so I'll keep my flags, err.. fingers crossed.

KOPBET.

 

[Mad-Mic]

I noticed your gears are 2.59. Mine are 3.07. I guess this could have a big impact on mpg?

Thanks,

KOPBET.

not really a big impact on mpg probably not even noticable. just noticable from a dead stop romp at 65 mph i'm at about 1700 rpm i think.

 

[JohnnyC]

I average 16 mpg right now mostly city and stop and go highway(for the past year been at 14-15 mpg)... probably get close to +25 when crusing on highway. But rarely get long trips like that.

My favorite is to watch the instant miles per gallon go really high when punching it a little and then coasting... i got to 108 mpg one time! If only that could really be true.

I get many, many more "s"miles per gallon.

John

 

[Alex D]

I used to have a 96 LT4 Vert and with that car I used to get up to 27 mpg on the highway and interstate and around 17-19 in town........now I have the LT1 auto coupe with the perf. axle and I get about 24 mpg on the interstate and 17-20 mpg in town......this is all based on the dash display which seem sto be fairly accurate

 

[86-ZZ3]

How does the computer calculate fuel consumption? Does it use X number of pulses a second multiplied by the amount of fuel per pulse (I assume this is a programmed number based on assume fuel pressure and fuel injector capacity), and distance travelled in the given time?

 

[Towu4free]

lt1...bad mileage

i read most of these posts and im very confused. i have reset my mpg avg alot to see if i got anything diff but my car avgs around 15mpg...this is a 50/50 mix between highway and back roads...granite im on the throttle maybe once a trip but ive tried being easy and it only jumped to about 16 avg....is there something wrong with the car or...is is modified? let me give you a little info on it and see what you guys think.. i bought it about a month ago and they guys wife apparently was a corvette nut or something anyway i got it home and decided to clean the throttlebody...well upon cleaning it i noticed it had an AIRFOIL, and has had the throttle body coolant bypass done on it...i done a tune up on it plus fuel pump and regulator and now the car runs good...VERY good it actually does what feels like a double shift when its to the floor it goes past the 6K rpm mark too....what do you guys think? is it modified? thanks

p.s my gears are 3.08 i believe..the performance ratio