Oil differentiation between diesel and auto applications

[RedHawkRidge]

Okay, after doing extensive search of several related locations on TBN, I can't find anything addressing a pretty basic question:
It seems to me that maybe 6-8 years ago motor oil became highly specialized to the application. Specifically, the oil bottles today have a gear symbol on the front that specifies "for diesel" or "for gasoline" engines.
Am I confronting a classical marketing scam by the oil manufacturers, in which they create the notion of different products for different applications, yet they are all pretty much the same? Seems like 10 yrs or so ago, all motor oil was motor oil, whether the engine was diesel or gasoline.
So, I have a goodly stock of oil (sythetic and sythetic blend) that I bought without realizing their label said "for gasoline" -- am I committing a major boo-boo by using in my diesel CUT?
If there is a difference, what is it?
thanks,
Jim

 

[RickB]

Additive packages are vastly different between gasoline engine oils and diesel engine oils. Always look for the API service rating on the container.

http://www.api.org/~/media/files/ce...iesel/publications/mom_guide_english_2013.pdf

 

[DEWFPO]

Gasoline and diesel motor oils have always been different and for good reasons. Some diesel oils are also rated to be run in gasoline engines but I have not seen a gasoline engine oil rated for diesel service.

DEWFPO

 

[3930dave]

Motor oils have become more specialized, largely driven by pollution regs, and higher specific output production engines.

The short answer is - find out what Cx diesel oil spec your CUT was designed for. Any oil that meets that Cx (for example CF) spec, or later (ex. CI), will work as long as the viscosity meets the tractor manuf. spec. Do not use use a Sx gasoline only rated oil in a diesel engine - that is asking for trouble.

Bob is the Oil Guy is a good site to dig into the details of why oil has changed. Way back, many oils that were marketed for gasoline engines were also Cx rated, but that is not commonly done today.

To simplify, some people now use something like Rotella T6 for both diesel and gas engines. They are often advertised today as Fleet oils..... but you still have to check your relevant Cx or Sx specs....

Rgds, D.

 

[MHarryE]

The API ratings go way back. S oils are for spark ignited engines. The first API rating was SA which is okay for engines built before 1930. Sludge, sticking rings, all kinds of bad things go with old API oils. I believe SN is the latest API oil spec. With the new oils the auto makers can run higher engine temps without sludge problems. Oils like API SE are not for use in engines built after 1979.

C oils are for compression ignition engines. The major issue is that compression ignition engines have always had a soot problem and the C oils deal with that. If your gasoline vehicle engines are like mine the oil stays rather clean looking for thousands of miles while Diesel engine oil is black shortly after changing.

Emissions really became significant in diesel oil with CJ rating. Ash deposits from oil are an emissions problem so CJ oils take care of that. With older engines that isn't an issue but you might find it difficult to buy oils today that don't meet CJ because CJ is backward compatible.

 

[Gary Fowler]

I use the Shell Rotella T6 full synthetic in everything. It is rated for diesel but ok for gasoline engines. Diesel oil requires higher detergents and suspension agents to handle all the soot but those additives have no effect on a gasoline engine other than making them super clean on the inside which is a good thing.
I suspect that you could do the same thing with any brand of oil for diesel engines but don't ever use an API Sx grade of oil in your diesels . There may be an SN rating out but I think the latest I have seen on oil containers is SL, but that doesn't mean there isn't a new rating. It takes the oil companies a while to get their oils certified to meet the new requirements after it is issued.

Bottom line, use your stockpile of Sx rated oils in your gasoline engines. As for storage duration, I don't think there is a limit on how long you can keep oil on your shelf as long as you don't contaminate it. You may want to give it a good shaking up if it has been setting around for a lot of years though just in case some of the additives have settled out. I don't know that they will but it never hurts to shake things up a little.

 

[RedHawkRidge]

thanks to those responding. I've got 4 diesel powered toys, which are my "special" possessions. My practical/frugal side says "only use what is recommended and specified". But my go-the-extra-mile side says "if the manual says use X at Y frequency, then use X-prime at half the interval".
Glad to learn the facts on engine lubrication -- thanks again.
jim

 

[Copperhead]

viscosity plays into this also. True, CJ-4 diesel oils are engineered for the emissions stuff on diesels now, but there are still plenty of CI-4 oils around that work fine in pre-emission motors. But CJ-4 is fully backward compatible with previous HDEO specs. Where things will get goofy is the newer specs being developed now. Right now, called PC-11, but no one is certain if they will follow the "C" chain like the previous versions... probably not going to be a CK following the present CJ classification. It will NOT be backward compatible with previous specs. When it comes out in the next couple of years, folks are really going to have to pay attention to what they are buying.

Many diesel rated oils will work gasoline applications, as most of them meet at least API SM. I know of no diesel rated oil now that meets the API-SN standard that has been in place for a few years now. This mess will only get worse as the years progress. OEM's are demanding specific classifications for their motors and general classifications are not being recommended. Part of it is government emissions and fuel mileage concerns, some of it is the OEM's getting wild about design specifics with their motors. Like the GM dexos1 type of spec for example. One aspect of the spec is NOACK, or burn off rate. Any oil that is able to meet the spec must have a NOACK number less that 11%. There is virtually no conventional oil that can meet that low of a number. It requires at least a synthetic blend. And the specs are going to get tougher down the road.

 

[MHarryE]

http://www.api.org/~/media/files/ce...iesel/publications/mom_guide_english_2013.pdf

Here is the link to API. SN oils are to be used in all spark ignited engines built after 2010. SM oils are okay for 2010 and older.

 

[WilliamBos]

Shell Rotella T is spec'd for gas, diesel and many other applications. If you can run it in all, go for it.