Is Costco Kirkland diesel rated 15W40 OK in gas farm tractor? It's also "SN" (?) rated.

[sixdogs]

I bought some Kirkland (Costco) diesel rated oil for diesel tractor summer use. It's rated for that and shown in these photos.


But I just noticed it's also rated for gas engines--I think--because it has an API SN rating. Does that SN mean I can use in a gas tractor as well?

I know not to use diesel rated oil in a modern gas engine but this oil appears to be rated for gas and diesel. Is that what these ratings mean? I'm kind of an oil geek but never encountered a dually rated oil not clearly labelled as also for gas engines.

 

[MAX-24-Dean]

If it is an older gas tractor, I wouldn't have any concerns using a dual rated oil.

Why I wouldn't use oil that is rated for diesel engines in a gas engine;

Detergent additives can remove built up factory applied coatings in the cumbustion chamber that could eventually lead to blow by and incresed oil consumption.

The zinc additives in diesel oil have anti wear properties that are not typically compatable with newer gas engines, older engines I would be fine with.

Added phophorus in diesel oil can burn up a catalytic converter on a gasoline engine exhaust system,

 

[Midniteoyl]

Should be fine. The CJ/CK + SN oils are usually for mixed fleet use for off-road vehicles w/o a catalytic convertor due to the higher additives that could shorten it's life.

Edit: found this on Bob is the Oil guy:

Typically a CJ4/SN oil is an HDDEO which means the additive concentrations (mostly dispersants) are much higher. The CJ-4 (and soon to be CK-4) oils have a completely different set of engine test requirements and so the formulating approach is different. A HDDEO will typically have a DI which is 15-20% and a PCMO will be 6-9%. When an HDDEO is dual rated that means it also passes all of the required engine tests for SN - however it does not meet the "Resource conserving" requirements including fuel economy benefits and phosphorus retention. In some cases the limits on Phosphorus are also waived for CJ-4 oils so you may see one with more than 800 ppm phos still claim SN. This is not good for the catalytic converter and has been removed from the CK-4 formula (all CK-4/SN oils will have to have 800ppm phos max.)

The primary role of dual rated HDDEO is for mixed fleet use - where a fleet manager doesn't want to carry 2 oils for each engine type.
I wouldn't say that one is better/worse than the other, they are just different.

 

[Yander]

I would use it. I bought a brunch of Costco oil when it was on sale. It's as good or better than the name brand.oil probably. Just doesn't have all the marketing and brand overhead added to its cost.

 

[sixdogs]

Should be fine. The CJ/CK + SN oils are usually for mixed fleet use for off-road vehicles w/o a catalytic convertor due to the higher additives that could shorten it's life.

Edit: found this on Bob is the Oil guy:

I searched Bob The Oil Guy and didn't see that.
Good that you found it.

 

[sixdogs]

I would use it. I bought a brunch of Costco oil when it was on sale. It's as good or better than the name brand.oil probably. Just doesn't have all the marketing and brand overhead added to its cost.

After researching Costco synthetic API/gas engine oil and being familiar with the refiner's products, I switched gas cars and gas light truck to it from Mobil 1. It works and rates higher in additive package. Plus it has a little color so I can see the dipstick level after I change it.

Tractors still get 15W40 T6 Rotella and older Ford diesel truck Rotella semi-syn 15W40 because OEM calls for it.

The old Super C Farmall parade tractor gets pricy Royal Purple old car oil with higher ZDDP but now might get the Costco 15W40 with a ZDDP additive added to it. 100 miles a year.


In many decades of being an oil geek, today is a golden moment of easy choices between excellent oils and simple decisions. It was never this easy. The worst oils of today is probably much better than the best oils of not that long ago.

 

[Williy]

I read someplace the royal purple is like slick 50 it will crystalize now
the race drives sware by royal purple but they only put 500 miles or
less on a oil change

https://www.dodgetalk.com/threads/steer-clear-of-royal-purple.249570/

willy

 

[DarkBlack]

All the analysis I’ve seen of SN rated diesel oils, show phosphorus and zinc ppm’s hovering around the 800 mark, which is the government limit on gasoline oil to protect catalytic converters.
The diesel oil analysis I’ve seen that are not SN rated, all show phosphorus and zinc in the 1,000-1,100 range.
I specifically avoid the dual C*/SN rated oils for my diesels if possible, for that reason

 

[5030]

I bought some Kirkland (Costco) diesel rated oil for diesel tractor summer use. It's rated for that and shown in these photos.

View attachment 978683View attachment 978684
But I just noticed it's also rated for gas engines--I think--because it has an API SN rating. Does that SN mean I can use in a gas tractor as well?

I know not to use diesel rated oil in a modern gas engine but this oil appears to be rated for gas and diesel. Is that what these ratings mean? I'm kind of an oil geek but never encountered a dually rated oil not clearly labelled as also for gas engines.

Interesting comment as I use and have used for years now, Shell Rotella T6 in everything from my wife's ZTR to my inverter genny to all my diesel powered tractors and standby generation. Even my Ford Focus RS Turbo gets 5-40 T6 and so does my wife's Suburban LTZ. I want and use just one brand-grade of motor oil.

Far as I'm concerned a lot of oil 'myths' are just phooey.

 

[pacosperson]

I bought some Kirkland (Costco) diesel rated oil for diesel tractor summer use. It's rated for that and shown in these photos.

View attachment 978683View attachment 978684
But I just noticed it's also rated for gas engines--I think--because it has an API SN rating. Does that SN mean I can use in a gas tractor as well?

I know not to use diesel rated oil in a modern gas engine but this oil appears to be rated for gas and diesel. Is that what these ratings mean? I'm kind of an oil geek but never encountered a dually rated oil not clearly labelled as also for gas engines.

I bought some Kirkland (Costco) diesel rated oil for diesel tractor summer use. It's rated for that and shown in these photos.

View attachment 978683View attachment 978684
But I just noticed it's also rated for gas engines--I think--because it has an API SN rating. Does that SN mean I can use in a gas tractor as well?

I know not to use diesel rated oil in a modern gas engine but this oil appears to be rated for gas and diesel. Is that what these ratings mean? I'm kind of an oil geek but never encountered a dually rated oil not clearly labelled as also for gas engines.

I guess it depends on the gas engine application and usage. MANY years ago I was told diesel oils do not have the 'anti-foam' additives used in oil for gasoline engines. The gasoline engines rev much higher than diesel engines and, when used in high revving engines, diesel oil can foam up and reduce lubrication. Made sense at the time. That's why they install 'windage trays' between the crankshaft and oil pan in high revving V8's.