Motor Oil

Recently, I felt the car engine became more noisy, especially the valve lifters. So I suspected that the motor oil I am using may not did a good job. I searched on the internet and try to find a better motor oil. But suprisely, I found that many people complained about the new API SM standard. The SM standard oils are limited the usage of ZDDP, which is the anti-wear additive in the motor oil. However, the ZDDP will damage the catalytic converters so EPA asked the motor oil manufactures to eliminate it in the motor oil for gasoline engine. Most oil makers use Molly instead. Only few oil makes are still using ZDDP as the main anti-wear additive. AMSOIL, RED LINE, and MOTUL are the few available oils in US still using ZDDP. But they can not get API approval for their products because of the high ZDDP. That is why no auto parts stores carry them.

Some Porsche drivers/mechanics suggest to use Diesel CI standard 5W-40 synthetic oils on their Germain engines. The website has some pictures showing worn engine part at 35,000 miles using Mobil 1 0W-40 oils recommended by the Porsche.

I am not sure putting Diesel oil into a gasoline engine is a very good idea. But does anyone have a suggestion? Has anyone used Royal Purple before? Is it a better choice?

By the way, most synthetic oils on the current market like Mobil and Castrol are just Group 3 based oils. Mobil 1 oils used to be Group 4 based. Group 3 are highly refined petroleum and have better charactors than the regular oil base, but they are not vary much better than the ordinary motor oils in terms of protecting the engine parts. For most people, they are just waste of money and false feeling of better protections.