A good question. Yes, there is a difference. You want a commercial grade oil. The round circle on the container gives the API rating. There are 2 classes, S and C (service and commercial) they will be shown with another letter that indicates what level of additives it contains, in alphabetical order, the higher the letter, the more current the rating. sA, sB, sC, sD, sE, sF and so on. There is a new one coming, I think it is sL. To further confuse, Commercial oils do the same thing with a "C" prefix- cA,cB,cC, and so on. These contain additives and detergents for diesel engines. The most commonly found oils for diesel service are single weight, 20, 30, and the multiviscosity 15W-40. These will show both S and C ratings like SJ/CH. Most 10W-30 oils you find on the shelf at Walmart and other common suppliers is S rated for gas engines. I had to go to a Chevron oil jobber to get Delo 400 10W-30. This is not to say you wont find it immediately, but if you check the API label you will find most 10w-30 oils are SJ rated and very few carry SJ/CF. 15W/40 is excellent oil but in smaller engines it is a bit heavy. I used it in my 24 HP Case and it did not generally get hot enough to get the oil flowing really good. I think it is intended for diesels that run for hours or days without shutdown, rather than short light duty runs that most of our homeowner tractors see.
