Would you advise to use Mobil 1, 15W-50, on 1988 Porsche carrera or just mineral oil of the same viscosity? The car has 29,000 plus miles on it. If the answer is 'yes', then how long before I change oil?My mechanic is lukewarm about using synthetic oil. Appreciate your reply. Thanks

 

Sorry, missed this post stuck down here at the bottom. You can run 15w-50 mobil 1, but there really is no reason to in your engine. The engine came from the factory, and probably has used dino oil all of it's life. You would gain absolutely nothing by changing to synthetic. Castrol 20w-50 is a perfect weight for your car.

The other problem is, most synthetics go about 10-15k miles between oil changes. Even with a synthetic, you should still change your oil at minimum once a year, but I recommend every 6 months. If you are only driving the car 4k miles a year, then that is a lot of wasted money in synthetic oil when you go to change it out in 6 months to a year.

 

I agree with the post. I would add a caveat that if your car is not designed or been tested for synthetics is would be a risky choice.

Regular oils protect up to alower temperature (415-425 Deg).The synethics protect to about 475 deg. The issue is if the oil temp gets above those temperatures the synthlose lubricty very quickly. Strangely the natural oils start to break down at lower temperature but continue to provide some oil lubrication above 475 deg. They begin to create varnish. This is why you are beginning to see blends of both oils.

Syn tend not to provide lubrication longer and provide better friction protection. They are better oils! Theproblem expecially in a air cooled car is you most likely have "hot" spots that make syn a bad choice. The Porsches are oil cooled all most as much as air or water cooled.

I would recomend you stay with the manufactuers recommendation. If you are interested in syn go to the dealer and have him pull out a service bulletin. If they are allowed by the manufacturer than you have a choice. Most air cooled engines do not allow syn becasue of the hot spots I mentioned.

Interresting my 996 has oil change (not filter) recommendations every 15,000 miles or once a year. The new 997 has 20,000 miles or every two years whichever comes first.

Good luck,

Lee