What Kind/Brand of Oil?

[Manolito]

I used Castrol 20W-50 GTX for 30 years in cars and motorcycles. No problems. Three cars went over 250k miles each. Then I got a a couple of 5 qt jugs that looked like 90W. I tried it in one '97 BMW and the Volvo and they both sounded awful on cold start. I sent a sample in to BP (owner of Castrol) and they tested it and reported that it was "within blending specifications". I asked if their specification is simply "will pour out of the jug".

Switched to Mobile 1. Problem - I cannot keep it in the engines. I have changed valve cover gaskets in both '97 328 BMWs. Changed valve cover gasket twice in the '91 Volvo. All three still leak. One of the '97s leaks badly. Tonight the wife came in complaining that her 2004 330 BMW smokes and stinks. You guessed it - leaking valve cover gasket.

This is ridiculous. I have to switch to a different oil. The '97s and the '91 can go back to dino oil, but the 2004 has to be synthetic.

What do you folks use?

[JhwShark]

I don't think I'd put 90w in my car/engine...maybe in a differential.

but to your ? I use what you used to use and I have always used it over 30 years in all my cars without any issues. Even the MGB. I do not have cars that require synthetic's.
I did use penzoil on my first car -- VW bug, then the engine blew and I put in Koblensmith/Porsche engine parts and started the Castrol. No more engine issues.

Some people use Mobile 1

Jon

[Yurick]

Can you go back to whatever you used to use before all the leaking started to see it it still leaks?

[Manolito]

Yes. Unless I can find something better, I will probably go back to GTX in the three older cars and Castrol Syntex in the 330. I will probably replace the valve cover gaskets again when I change the oil.

[coolbear1]

I had the same problem with the Mobil 1 synthetic. I used it one time and It was like I put blood thinner in my engine, and it started to bleed to death. I thought it was just me. Never had a problem with GTX though.

Consider this, when you convert a car A/C refrigerant from R-12 they recomend changing the oil to the POE synthetic oil because the R-134a refrigerant does not readily mix with mineral oil, when you do change the oil, they always recomend changing black rubber O rings in your hose fitting connectors to the green O rings. It is not because of the refrigerant, it is because the POE synthetic oil attacks rubber.
The green neoprene O rings are able to resist the agressive nature of the synthetic oil.
Kinda makes you think doesn't it, like maybe the synthetic motor oil people aren't telling the whole story.