Buck.

I drive my 993 on the weekends and do a fair amount of autocrossing. I only put 3-4k miles/year on the car. I do try to run it at least weekly enough to get the oil up to temperature. During autocrosses the oil temp does get elevated (about 9 o'clock position).

Since I don't come close to the mileage interval how often (in months) should I change the oil. I run Mobile 1 15w50. With petroleum based oils I had always heard it was six months. Does synthetics increase this interval?

Thanks!

Chris in Detroit

Owners Manual says 15k miles for oil change, but note Workshop Manual says 20k KILOMETRES which equals about 12k miles

I think even 12k miles is a long time - not sure how many / how hard you run the autocrosses, but 3-4k miles between oil changes is a pretty good schedule.

So once a year should be fine for you.

Ray Calvo

I go 6000 miles between oil/filter changes. No problems with 993 (58K miles) or old '84 Carrera (120K miles when sold)