[2FastLX]

I switched to Mobile 1 tri-synthetic oil after 135,000 miles and never developed one leak. But then again it never had any leaks before I switched. But I agree with Medic. If you have a leak already it will probably get worse.

There is also a slight performance gain to be had with synthetic oils. I saw an article where they gained 8rwhp by switching all the fluids to synthetic. That's not a lot, but every little bit helps.

Another benefit is the cleaning power of the Mobile 1 oil. I religeously changed my oil every 3000 miles with the petroleum based oil. When I pulled my valve covers there was a slight film of sludge. I switched to Mobile 1 and ran for around 5 more oil changes or so (at 4000-5000 miles between each oil change) then had to pull my heads to replace the head gaskets. To my amazement when I pulled the valve covers they looked like a brand new set of heads. Not a spec of sludge to be found anywhere. Even the lifter valley looked like a freshly cleaned block. I was very impressed and now swear by this stuff. It may be more expensive, but to me it's one of the best things you can do for your engine...high mileage or not.

Another thing that I think may have helped though is I was running the K&N oil filters. The oil seemed to stay clean longer when I swicthed to them.