I just read a cat oil spec sheet and they do not recommend mulit weight oils in p/c engines, Does anybody know the WHY of this ? I have been using Rotella 15-40 with no problems. I am not in the excavating business and the machines see light use on my own property.
We've been running 15w-40 in D-8s for 30 years the oil is the least of our problems. Bob
What do you mean by P/C engines?
I think he is referring to older Cats with the pre-cumbustion chamber style heads. My thoughts without looking up Cat's recommendations are the spec's were written back when multi'viscosity oils were not recommended for any diesels. Now days about the only diesel that I know of that still recommend straight weight oils are the older 2-stroke Detroits.
Was the spec sheet specifically recommending against multi weight or was it just an old spec sheet from when multi weight wasn't really popular? Detroit came out with a document that is much more up to date that tells you not to use multi weight in 2 cycle engines even after it became robust and reliable. But like the others, I am not aware of anything in a PC Cat engine that is different than any other engine. Old Detroits are a lot different.
I know the original question was about a Cat p/c engine but as the question also relates to straight weight oil and I had mentioned the Detroits here is the latest I was able to find about the Detroits which are now covered under the MTU line, it is dated 2015. Go to page 20 for the two stroke 53, 71,92 and 149 engines info: https://www.mtu-online.com/fileadmi...specifications/neu_01_04_2015/A001061_36E.pdf
Some models run a cooler clutch off the engine reservoir. Any wet clutch or wet brake will shear the viscosity modifier (the polymer that makes multi-weight). This will lower the viscosity of the oil, reducing the protection of the oil.