Have a '99 c2 coupe with Z rated tires.(28,500 miles) My mpg seems to be pretty low,about 17 cty and highway combined.When I am on the express way I can see the gas gauge going down as I drive. Has anyone tried nitrofill in their tires? Any other suggestions for better mileage?

 

Keep pressing hard on the accelerator and don't worry about MPG

 

In addition to the gauge problem, do you ever drive in the rain. Bet your back end wobbles like hell with 28,500 miles on the back tires. Get on your knees and take a look at the inside half of the tires. Let us know how many steel bands you can see popping through the rubber.

 

If I drive my 99 C2 on the highway (85-90mph), I get ~23-24mpg.
In town I get ~18-19mpg.

 

I am getting 32mpg highway since installing the supercharger

 

At what speed......???

 

We use nitorgen to decrease pressure changes when racing but what do you think it's going to do for your mileage? Just curious.

 

If your tires are not worn out from the 28,500 miles on the back ones, then you are obviously running with an incorrect rear camber. This means that more of your tire is making contact to the road surface increasing drag. Are you running 36 psi front and 44 psi back?

 

My highway speed is usually around 80.I bought the car last year with 24,000 miles on it. I put new front tires on the car about 5 mos. ago .No has told me my rear tires are worn.(I had service twice, oil change,ignition replacement.)Front psi-36, rear psi-40.

 

Since I am new to 996 ownership, can I assume from these posts that if the car is correctly aligned, the rears wear on the inside shoulder?

 

Then I suspect that your rears DO NOT have 28,500 but were probably replaced before you bought the car. Increase rear pressure to 44 psi for street and highway driving and put a bottle of injector cleaner in the gas tank. Also, if you are calculating your gas mileage by the computer display....don't. Keep track of the miles driven and calculate your mileage manually when you fill up each time.

 

Yes, you are correct. The car is setup with a negative rear camber which puts the majority of pressure on the inside half of the rear tires when driving in a straight line. This allows you to be a little more aggresive when cornering as the tires will be forced to a neutral camber, putting the full width of the rubber to the pavement. It also allows for full tire contact when the backend is pushed down, such as quick acceleration.

 

Unless there IS something mechanically defective with your car/tires/pressures, etc...it would seem to me to be a function of the lead...not in the gas, but in your foot. I could drive up to, 70 mph or whatever, and cruise there and get great mileage. If I push and pull, drive aggressively up to, say 50 mph, back to 5 and up again...surely the mpg becomes gpm. So if you want better mileage, ease off and smooth it out and you'll do better...after ensuring that the car, etc. is optimized mechanically.