These were such great reads, thought you guys may like em. Evidence-based recommendations carry much more weight with me than conventional wisdom and standard rhetoric.

Synthetic oil comparison:
http://neptune.spacebears.com/cars/stories/oil-life.html

Mobil 1 results:
http://neptune.spacebears.com/cars/stories/mobil1.html

On my old engine, I changed oil with regular 10w30 every 3k. I switched to high mileage oil with seal additives around 80k. All I can say is that engine still runs like a champ, b/c I never took it apart to inspect bearings or cylinder walls.

On the new built engine, I'm running mobil 1 15w50. Based on this study, I'm going to go between 9k to 10k between oil changes, with the caveat that I'll do an oil analysis at 5k. If it all checks out, 9-10k will be my new interval. Oil analysis is cheaper than adding more mobil 1, and the diagnostic info should be enlightening.

Thanks. Those were both good reads. I found the wear metals particularly interesting. I've ran the Mobil 1 5000 miles for years. Now I'm considering doubling that-with a filter change at 5000 and a top off.

Nice find, I have wondered about syn oil for a while. Is there any truth to switching right from conventional to syn about leaks? Also, if my car is slightly burning oil now, would the synthetic oil be consumed faster than conventional?

Originally posted by 740 turbo brick
Nice find, I have wondered about syn oil for a while. Is there any truth to switching right from conventional to syn about leaks? Also, if my car is slightly burning oil now, would the synthetic oil be consumed faster than conventional?

The only engines that I've ever had issues with synthetic causing leaks or leaking more on were my old air cooled VW/Porsche engines. I had to jump from a 10w30 to 15w50 to keep things from leaking (more) on those. I have actually noticed that certain synthetics seem to have different properties when it comes to consumption. my Subaru's always consume some oil, it's just an odd quirk of boxer engines. I have found that different brands of oil have different consumption rates in the subarus. mobil 1 5w30 I have to top off half a quart every 1500 miles, where as castrol syntec I only top off half a quart every 3000 miles.

Generally speaking synthetic is much "thinner" and will leak quicker than conventional oil.

Originally posted by Nemo
Generally speaking synthetic is much "thinner" and will leak quicker than conventional oil.

No, it really isn't. viscostity is viscosity. Viscosity ratings are determined by newtonian fluid laws and don't change. Synthetic is much more accurate to it's viscosity rating and is refined with longer carbon chains which is why it doesn't break down anywhere near as quickly as conventional oil. the reason it seeps out of engines like my aircooled VW/Porsche engines has to do with the thermal expansion/contraction of the engine itself and the different thermal properties of the synthetic oil.

what some people may have issues with is the detergents in different brands of oil cleaning out gunk and gumming that has built up in seals and gaskets. once that gunk is gone it can open up a nice freash leak. synthetics are better at distributing detergents.

Wow! Thanks. Perhaps it just opened new leaks in my Jeep because when I switched to Mobil 1 I had to top it off twice as much as before over the same milage. It sure does apper much thinner. It seems to reduce drag on the motor too. Is that just because it's more efficient?

Originally posted by Nemo
Thanks. Those were both good reads. I found the wear metals particularly interesting. I've ran the Mobil 1 5000 miles for years. Now I'm considering doubling that-with a filter change at 5000 and a top off.

Just a note, Mobil Clean 5000 is not synthetic oil; it's Mobil's conventional counterpart to Mobil 1.

Great info EZ!

I switched to Max Life at 254k, I can DEFINITELY tell a positive difference in the oil burnoff and the like.