No matter how carefully I drive, my avg. mpg is 14 in city! 18 on highway. How are some of you guys getting over 20mpg???

What the heck is wrong with my Vette?!?????

 

Maybe it's not the Vette.....

 

I get 19 around town and about 28 on the HWY according to the DIC.

 

you have an a4?

 

Did you reset it??

 

Any mods, what is your mileage, have you performed the routine maintenance? Also the oxygenated gas that is used in some states in the winter will reduce your MPG and if you don't keep your tires properly inflated in the colder weather that could increase rolling resiance and decrease your MPG.

 

Assuming NO MODS (other than external to the engine and/or drive train):

First question:

Are you relying on the DIC (computer)?

If so, do you remember to reset it?

If not, you'll get a skewed indication of mileage.

I would suggest you try computing the mileage by 'manual' means.

Next, are you computing the milage by 'manual' means?

If so, and the numbers are as you indicate, there is something not correct with either:

-your driving methods, and/or

-the mechanics of your engine (or engine train), and/or

-the way computations are made.

 

Doc

I had a 98 MN6 also and got very good MPG figures. The 18 combo city highway sounds about right. The secret for me in getting excellent highway MPG was to get in to 6th as early as possible and be easy on the tap. I have seen as great at 31 and as lousy as 16 on the highway. (We all have to play hard sometimes!! ) The very best MPG that I have seen was obtained on I-95 here in CT. It was one of those rare times in the spring when the traffic was stacked on the highway but every one was doing 60 MPH in just about bumper to bumper traffic. Very steady constant pace!

The Ls1 is a very strong engine and as long as I can keep the RPM's above 1500, I'm in 6th. Granted, being in that gear will not allow you to accelerate very fast but it will keep the car going without a sweat and you MPG will be way up there! If you need to get the lead out, drop her in second!

You will see slightly lower MPG figures as the temperature approaches or drops below around freezing. The air is colder and denser and needs more fuel to keep the same AF ratio. Some cold weather states mandate oxygenated fuels and or add alcohol to the fuel to minimize exhaust emissions. These do not help fuel economey!!

I drove my 98 to Mass once and it was near zero out when I left home. I was NOT able to get the MPG above 22 and I was driving with economey in mind !

Stop and Go traffic kills the fuel milage in the C4 and C5!. I work on a Navy base and the TOP speed limit on the base is 25. Lots of traffic and stop and go is the norm!!! If I fill up my car and reset the meter on the 98 or Z06 and go on to the base, I will see at best 12 MPG

Another factor is Mods and your state of tune. If someone adds mods to increase HP/TQ, some of those mods will require your PCM to be tuned to maximumize the Mods effectiveness and to recalibrate the A/F Ratio for efficiency!

I added Stainlessworks LT headers, high flow CAT's, 3" midsection with an "X" pipe and the Stainlessworks 3" high flow mufflers. My "EXCELLENT" MPG that I was averaging on the Z was 29-30 highway plumeted to a best of 25-26.

The car runs EXCELLENT!!! Gobs more HP/TQ. The sad fact is all I need to do is to get it professionally tuned to get my MPG back to or even maybe exceed the old 29-30 and the tune may even get out a few more HP/Tq as icing on the cake!

I have to make my mind up as to purchasing tuning software and trying to do it myself or having someone do it for me.

Decissions,,, Decissions!! The car is in somewhat of a winter storrage, so ,,, I have time to figure it out.

Please explain the following;

How many miles on your car?
Do you have any Mods?
What kind of fuel and octane level of do you use????
When was the car tuned last and what was done?
Please read amd post all of your CODES that are in memory.

Is your car running smoothly?

How and where do you drive the car???

Maybe I can figure out something for you.

Bill

 

I have never gotten more than 14 mpg on my z06...usually 12.8. My 00 FRC averaged about 14.6.

 

I'd say you have a problem. 18mpg on the hwy seems way low to m? With all my mods I still get 30-32mpg on the highway. I adverage 20mpg and that's with 80% in-town driving and stop grand prix's at that.

 

Are your numbers from the DIC display or from your calculations at the pump? In other words... have you verified that the problem is not the DIC calculations.

My milage number numbers are very low... with good reason

My accelerator basically has 2 positions... On and Off

 

i'm right with you DrValidus. i actually average lower than you, 12 city. i thought there was something wrong with the car too but as Bill Curlee stated, our state does indeed use oxygenated gasoline and it does affect our fuel efficency.

and as for highway driving, i also averaging 18mpg. but i'm sure you'll agree with me on this, highway driving anywhere around the NYC area is not equivalent to interstate highway driving. highway driving means the car maintains a constant speed (70mph?) for an extended period of time - unlike NYC hwy driving where we'll hit 70 then have to slow down because some idiot is cruising at 45mph in the left lane! or there's an accident/broken down car every 5 miles. on a good note, just yesterday i made a trip upstate and averaged mid-20's so i wouldn't worry too much about it.

 

Lack of information here. Its kind of like telling your doctor you don't feel good over the phone and having him diagnose what the problem is. Many factors can cause bad gas mileage. Maybe you have 4:11 gears? We don't know

 

O2 probe will fail safe to rich mixture when it goes out.

 

very helpful

 

Sounds like something is not right. I get 15-18 in the city, but on the highway, it is more like 28-32. If you haven't reset your average MPG lately, try that and then see what it says.

 

I have a 2004 coupe auto and get 22mph in town and 27 mph on the interstate driving 80mph on a road trip. And this is according to the dic. I always use 91 octane or above.

 

[QUOTE=bearman95]I have a 2004 coupe auto and get 22mph in town and 27 mph on the interstate driving 80mph on a road trip. And this is according to the dic. I always use 91 octane or above.[/QUOTE

 

There's nothing wrong with your car. It's where you live that's the problem. You live in NYC where there's a light at every corner and there a giant parking lot called the LIE (Long Island Expressway).
You're getting the same kind of mieage I was getting until I moved.

Once I moved out of NYC, my mileage increased to where it should be and my auto insurance dropped by half!

I'm getting 22-27 with my MN6. I find the DIC to be about 10% off. I divide the miles traveled by the gallons filled.

 

I get 20 in the city and 30+ highway with an A4