Oil?

[H. Miller]

We have a Cummins ISC 330 but my question is more general in nature. Having read most of the oil discussions there remains the question.......
What is the difference between a good grade of "normal auto oil" and oil that is labeled "diesel"?

[Sixpack98]

It's the additive package. Diesel and gasoline engines require oils developed for the type of fuel they use. Now that USLD diesel has replaced high sulphur content fuels the lubricity of the fuel is lower due to the process of removing the sulphur. Diesel oils have a new standard (CJ-4) that compensate for the loss of lubricity. There are other differences such as ash control, sludge prevention, acid, metal and oxide issues.

[GaryKD]

Hi Hal,
1. I think your Cummins needs 15W-40 multi grade weight. I have never seen this in oils made for gas engines.

2. The standards the oils are made to are different. Gas engine oils are made to ILSAC GF standards. Oil for diesel engines is made to API CJ-4, CI-4 Plus, CH-4, CF-4/SL standards. Both of these oils standards are made to API (American Petroleum Institute) SM standards and comply with all earlier API standards.