GF-4 vs. SM

[Brons2]

While bored on a road trip to Colorado, I actually took a trip to Wal-Mart just to check out motor oil. As predicted on this forum, I found the GF-4 rated Mobil Drive clean. This oil had an SL rating.

I also found the "synthetic blend" Motorcraft 5w30 that was SM rated. However, this oil had a GF-3 rating on it.

What are the differences between the two new ratings, and which is better? Will there be a dino soon that has both? Or is this even desirable, e.g., the API Starburst oils not necessarily being the best for wear? I eagerly await the experts

 

[TallPaul]

So far as I have seen the SM does not look like a good deal: Click Here

 

[Brons2]

Yeah but the loss of an A3 rating does not speak any insight to my original question. It could be possible that perhaps in your case Valvoline just didn't want to go through the trouble of certifying for A3 compliance again after the SM reformulation. There are a relatively small market for cars that require A3 rated oil, and I would surmise that many of their owners would prefer to use full synthetics. I suggest for your dilemma to get VOA's for both.

Now back to the original question!

 

[Brons2]

Here's a link that I found on another thread:

http://www.lubereport.com/e_article000229004.cfm

Interesting read. It says that SM is basically the API's companion spec to the ILSAC GF-4 spec. Difference being that API is used worldwide whereas ILSAC is not used in some areas.

 

[Brons2]

Another interesting read:

http://www.chevron.com/prodserv/BaseOils/gf4_faq.shtml

The part that struck me the most:

There is no engine test that measures emission system stability, but the OEM's have data showing that sulfur and phosphorus are poisons for catalytic converters and must be limited. Thus, in GF-4 oils sulfur is limited to 0.5%, maximum, in 0W- and 5W- engine oils and 0.7%, maximum in 10W- engine oils. Phosphorus is limited to 0.08%. This restricts the amount of zinc dialkyldithiophosphate, the workhorse anti-oxidant and anti-wear agent, which can be used in engine oils, which in turn, may restrict the amount of Group I oil in GF-4 blends.

It seems that the reason that better base stocks are being used is because the GF-4 spec reduces the amount of additives that can be used. It seems to me that it's somewhat of a tradeoff, and a better option would be an oil with the good basestocks and a robust add pack.

I guess this is why they say diesel oil is no good for cars. nevertheless, I would not hesitate to use it.

This site is a wealth of information!

 

[Gene K]

I believe the Motorcraft Blend I looked at had "meets proposed GF-4" on the back in fine print.

Gene