would you go between changes in a XK8?

 

This has been discussed many times on several forums. The answer is an emotional one based on your own research. Oil analysis would seem to indicate that a synthetic has a useful life far beyond the 3, 5, 10k mile recommended change intervals.

My own opinion, unencumbered by information or knowledge, is that a full synthetic is good for at least 10K miles and probably more.

 

but it seems that these motors (in a 97) and how they appear to me to be tempermental that I should go no more then 3-5k on oil changes.

 

Not knowing if mine has always had mobil 1 ran in it and now at 73k should I use a High Mileage formula Mobile 1?

 

In a perfect scenario synthetics should last longer before breaking down, but in a passengar it really doesn't make that much difference. Contamination is the number one factor breaking down oil. Therefore whether you're using a synthetic (really a misuse of term) or conventional dino oil regular oil changes are necessary. I would still change either dino or synthetics at 5K miles. Plus in a passengar the oil filter is the weak link. I wouldn't want to run the same oil filter for more than 5K miles on any car.

In a race car it's a whole different story. The number one enemy of oil in an race car is heat. This is where synthetics make a big difference. NASCAR motors run at 9,000 RPM with pushrods constantly for hours, Indycars at 12,000 RPM and F1 cars at a riduculous 18,000 RPM (300 revs a second), so the demands for a motor oil are quite different compared to street conditions. Oil companies are clever in using what's good for the track is good for the street marketing.

I would bet that if you did an analysis between regular Mobil 1 and the "high mileage" version, there is no difference.

 

Go to http://www.blackstone-labs.com and have them send you a sample kit.

Change your oil and 1/2 through the draining collect a sample. Send it to the lab and have them look at it. They'll send you a report and will tell you how many more miles you should go on the next change (the one that would be in your engine when you get the report). $18. for a report.

My 2000 XK8 has had Valvoline 5w30 dino oil since its first oil change. Your bearing ride on the oil film not metal to metal. The older the oil is the more dirt for the bearings to ride on.

Oil filters are just paper and can hold only so much. I change oil and filter every 3000 miles, even Mobil 1 used in one of my other cars. Oil is cheap..engines and their parts and labor are not.

 

lots of good info guys. I started using synthetic in my car when I got it used. It sounded really good when the guy was telling me that this car has tighter tolerances in the engine and a synthetic will protect it better, if BS, it was good. Ok, got me to start using it. I change it every 4-5k. Been happy, won't go back.

The most memorable advice i've heard from car enthusiasts is 'keep feeding it the same diet it has always had'. If it was dino oil, keep going dino (but perhaps go the higher mileage dino in the later years). If you start synthetic, keep using it. Now, that made sense.