I've gone from getting 300 miles out of a tank to a lousy 200. While I drive short distances, and it has been cold, this seems to be a new development.

Suggestions for my mechanic?

Spark plugs?

 

Hey there, I'm sure some of the model specific guys will chime in shortly, but in the meantime.......

What sort of mileage are you at?

If you're mileage is way up there assuming around 100k for a 14 year old car, it could be time to look at the 02 sensors, failing sensors will give false readings and you'll be running rich.

Any jerky / jumpy / hesitant periods at all?

Or it could just be down to the cold weather, the car taking longer to get up to temp, heated rear screens / heated seats etc etc all using more power which has to come from somewhere.

Typically I can be down around 4-5 mpg around this time of year.

 

No dramatic jerkiness. I had the sparkplugs replaced and my mechanic said it really needed it after he examined the old ones. It takes we weeks to get through a tank of gas since I drive short trips mostly, so I don't know if it will help. And the weather has become much warmer.

The only thing I noticed before, and still do, is a 1 second rhythm. You have to listen carefully or simply touch a finger to the sheetmetal.

I'm wondering if I should try Engine Restore and Lubricant ( Restore USA - Engine Restorer ) that other people swear by for their Nikasil motors. Since mine is a 2002, I suspect Nikasil was abandoned at that point, and I'm waiting to hear if that is advisable.

Thank you very much for your suggestions.

 

Restore won't hurt anything, so if you don't mind a little money for a solution in a can before you find the real issue, go for it. Some real data like fuel trims, etc off your OBDII port would be useful for the group in order to help you.

 

I'll gather that data in two weeks when my parts arrive from Gaudin Jaguar for my upcoming maintenance (oil cooling lines to/from front radiator + power steering line/cooler) and upgrades (R Pack larger front rollbar and bushings).
Thanks!

 

Check your thermostat has not failed open. If it has, the engine will not be able warm up properly and it will not go into closed loop.
Regards,
White Bear

 

If you're driving primarily short trips as you stated, there's your main culprit. Try to do at least a couple of long highway stretches and see if your mpg improves significantly....