I've noticed that Mobil's new conventional oil is rated SM-CF. I guess the CF means it is compatable with light duty diesel engines.
Someone correct me if the information I heard is incorrect. Someone told me that using oil rated CF in my gas engine may not necessarily be good. They didn't give me detail as to why they thought this however.
Have an of you heard that CF is not all that great for your as engine? Or, does it serve a benefit?

 

Lets look at the ratings and and see what they exactly mean. For your gas engine, all oils will start with an "S". This means Spark ignition. All diesel rated oils are marked by "C", meaning Compression ignition. Generally, oils for gas engines are light oils that have viscosity modifiers that enable the oil to be relatively thin at cold temps and will only thin to the respective viscosity rating at hot temp. The HDEO or diesel rated oils are generally heavy oils that have viscosity reducers that enable them to perform similiarly to the light oils.The rating of CF is an old rating and the current rating for current production is CI+. The difference is mostly to do with soot control, emmissions compliance, and better fuel efficiency for diesel engines. You can use a dual rated oil like the Mobil in your gas engine and older diesel engines. It cannot be used in the 6.0 Ford diesel. Hope this helps.

 

That being said, Mobil 5000 (conventional) is rated SM/CF..
Both together. So am I gaining a benefit by using this in my V6 gas engines or should I stick with a non-CF which is basically everything else on the market, ie..Castrol, Val, Penn, are all just SM rated.

 

Actually, that's what I thought too but it's not the case.

From API's website:

 

JSCHIRA,

Yes, I already know what the ratings mean...my question is simple..
Here, allow me to restate:

That being said, Mobil 5000 (conventional) is rated SM/CF..
Both together. So am I gaining a benefit by using this in my V6 gas engines or should I stick with a non-CF which is basically everything else on the market, ie..Castrol, Val, Penn, are all just SM rated.

All I'm askins is, for my V6 gas ensinge, which would be preferable: oil rated SF/CF which is the Mobil 5000 conventional, or SM rated everything else such as Castrol, Valvoline et...???

 

You aren't really gaining anything but your not hurting it either.

 

Why then isn't everything CF rated, and how come only Mobil conventional and how does Mobil sell their conventional oil at such a cheap price???

 

And my post was not directed at your comment. Read it again.

With respect to your specific questions, the "S" and "C" oil specifications overlap to some degree. So an oil meeting the "SJ" spec, for example, might also meet the "CG" spec as well.

So, why do some oils carry only the "S" rating while other carry both an "S" rating and a "C" rating? API charges to license its rating system. Also, if the oil is going to carry dual ratings, it has to be tested against both specs. Both cost $$$$.

There is no way an SM oil is going to meeting the modern CI+ rating, the specs are too far apart. So, the best that the oil blender can do is to meet a way out of date CF rating. Most oil blenders are going to figure it is not worth the money to get the CF rating, because no one is going to buy a CF oil for a modern diesel. For some reason, Mobil believes there is a good enough market for CF oils, it chose to dual-rate.

Buy the cheapest "S"-rated oil that Toyo recommends. If it also has a "C" rating on it too, that is of no benefit or no harm to you.

BTW - Don't over think your oil choices. It's not that complicated. Unless of course, you have nothing better to do.

Personally, I bought about 10 cases of Shell and Exxon at $0.59/qt. when PepBoys had it on sale. Got a bunch of QS and PZ at $0.89/qt. too.

 

grbr95, I would use whichever oil you can find in reliable supply and price. If you like to stick with one brand, then pick one you can get from a local supply by the case. Or one that you know you can get most anywhere.

And actually there is a niche for the CF rated oil. It's suitable for most off road farm and construction equipment. So a SM/CF rated oil is a good inexpensive multi-duty oil for a farmer or contractor who wants to simplify things with one oil.