best non-synthetic oil?

[publicenemy137]

Wondering which is the best oil out there. I know mobil-one synthetic is the best, so I am referring to non-synthetic oils. I don't want to hear "Oh this is the oil I use", just concrete evidence and facts why this certain oil is the best so I know what to use next time. I currently use Castrol GTX 10w-30 oil, I heard Castrol GTX oil is really good. I heard Quaker State was not so good, it doesn't have many additives and such.

[Akira13126]

I used to use GTX in my 1994 Geo, my mothers 1996 Subaru (driven hard on mail route) and her 1998 Mustang for the past few years. Never had a problem with it.

[publicenemy137]

damn no oil experts here?

[MagicRat]

Lets assume that 'best' means the most effective at reducing friction and fighting engine wear.

As we all know, the petroleum base stock that makes up about 85% of the engine oil is much the same for all brands. It's the additive package (15% of the volume) which includes anti-wear additives, viscosity index improvers, acid-neutralising compounds, etc, that makes the difference in the oil.

Patrick Bedard at Car & Driver wrote an article about this a few years ago and found the best oils were those specifically intended for diesel engines.

You know the ratings on the side of the botle? An 'S' rating means 'spark' ignition engines (gasoline) and the 'C' means compression ignition, like diesels.

Oils which were rated for gas or diesel engines (ie SJ/CD, or similar) are NOT the best. The best ones just show the compression ignition rating CC and /or CD, and do NOT have a 'S' rating.

This is because the best anti-wear additives will eventually contaminate the catalytic converter and render it ineffective IF the engine starts to burn a bit of oil. Oil manufacturers do not want to piss off the EPA or car owners by screwing up cats, so they use a slightly less effective anti-wear additive package in gas engined cars.

The problem is almost all diesel oils are rated 15W-40, which is a bit too thick for most gasoline engined cars.
What you want is 10w-30 or 10w-40 oil rated only for diesels (with no 'S' rating of any kind), but this is nearly impossible to find (I've looked).

I use 15w-40 in my air-cooled motorcycles exclusively. I also use it in my old cars in the summertime. They have higher mileage engines that are a little looser inside and really benefit from the slightly thicker oil.
I use gasoline-rated oils for all my other vehicles.

[publicenemy137]

so what brand is best then?

[fredjacksonsan]

Oil experts? Check out:

www.bobistheoilguy.com

Almost too much information there. Basically, any oil that has the highest "S" rating should be good quality. I used to use Castrol, but found it got a little sticky towards the end of the oil change interval. After that I used Valvoline for many years.

I've also tried the cheapo stuff at WalMart (89c a quart, can't beat it!) in an older car (18 yrs, over 140K miles)with no problems.

The info from the website indicates that most oils today are very very good. Shell Rotella and Havoline tend to come up in discussions quite often.

On my new vehicles I've switched to Amsoil synthetic, and go for 7500 miles between changes. If you have an older car you shouldn't go from dino to synthetic, as you'll probably get some leaks.

Hope that helps....

[fredjacksonsan]

Oh yeah, and the Quaker State thing...I did have a car, back in the 80's that I use QS on, and it did get some gunk on the dipstick. I've never used it since.