Hi,

I have a '00 SS Convertible 6-speed with about 24000 miles which used to get about 20-22mpg with the mix of city and freeway I am doing.

Lately I have noticed a marked decrease in mileage, down to 16-18.

One thing I changed around the time the mileage went downhill is change tires. My old ones were GoodYear Eagle F1 275/40ZR17 (OE) and the new ones are BF Goodrich Comp T/A KDW 285/40 ZR17.

I know that the tires have a tiny bit more diameter and my speedo is not adjusted, but can this really make that much of a difference?

If not what should I check?
- spark plugs (already?)
- I looked at the air filter and it looks ok (still the stock one)
- tire pressures are ok
- the 24000 mile service is due this week.
- I am using Premium of course

Any other ideas?

Thanks

Chris

Chris

 

O2 sensors is the only suggestion I can make.

 

Would I notice that during driving?

I have a PC interface but i havent hooked it up lately. Probably time to do so.

Anyone else have a suggestion?

Thanks

Chris

 

we'll it is about fuel filter time. The fuel filter is often an over looked item that causes all sorts of problems. The only other thing i can suggest is, Is your clutch slipping? When mine started to slip gas mileage went down as time went on. If you get on it hard, the tach shouldnt surge up before the car starts to accelerate. Those are the only things i can think off

 

Fuel filter sounds like a good suggestion. Ill dig out my repair manual tomorrow to find out where it is at and Ill check it.

The clutch is not slipping even under very hard acceleration.

Thank you

Chris

 

Fuel filter is located under the driver side right in front of the rear wheel. take your time, open the gas cap before you loosen it, Forget about the scrader valve to purge the pressure, it makes no difference. Use a catch pan and let the fuel drain into the pan before you rip the filter out and you or your drive way shouldnt end up covered with fuel.

 

I'll address that tomorrow. Is the fuel filter clear so I can check it without taking it out or is it one of those 'replace it to be on the safe side' deals?

Thanks

Chris

 

The fuel filter is enclosed in some sort of hard casing, so you will have to replace it

I just did this yesterday, and it is extremely easy. Have fun!

 

Yeah it is in a little craddle, and you can not see through it. I usually saw mine open once all the fuel is out of it just to see how dirty it is.

 

I need to replace mine, where do I get a replacement?

 

how owuld i know if my clutch was slipping? i have noticed ****tier gas mileage as of late.