Fleet oil analysis showed a HUGE difference between 15w-40 and 10w-30 in our Cummins ISX engines

After 6 months of testing 6 trucks at our depot outside Nashville, the wear metals dropped by nearly 40% on the 10w-30 fleet. Has anyone else seen that big of a swing in their own oil samples?

3 comments

3 Comments

the_holly20d ago

Old timers gonna old time, right?

skylerrobinson26d ago

Well I have to admit, I was one of those guys that thought 15w-40 was the only way to go for heavy duty diesels. But your numbers are hard to argue with. A 40% drop in wear metals is nothing to sneeze at, especially over a 6 month test with 6 trucks. I ran my own small fleet of three older Cummins engines and never bothered with 10w-30 because I figured the thicker oil was safer for high mileage. After seeing your results, I started switching a couple of my trucks over this summer and the first oil sample came back with noticeably lower iron and copper levels. It completely changed my mind on what I thought I knew about oil viscosity in these engines. I think a lot of us old school guys just need to accept that modern oils are better than we give them credit for.

hannahm3926d ago

My buddy runs a towing company with a whole fleet of older Fords, and he was dead set on 15w-40 for years. Swore by it, said thinner oil would wreck his 7.3L engines. I sent him a link to this thread and he laughed it off at first. Then one of his trucks started knocking in the winter and a mechanic buddy told him to try the 10w-30 just to see. He did one oil change on that truck and the next cold start was way smoother. Now he's slowly switching his whole fleet over and says the oil analysis is showing way less wear than before. It's wild how much difference it makes when you actually test stuff instead of just going with what you heard from the old timers.