Oil confusion

Herrmann_Sherman · Post by **Herrmann_Sherman** » Tue Jul 10, 2012 2:41 pm

Dear members, I´m very confused about the viscosity.
Some say that SAE 20W-50 is ok and others say for a Willys is SAE30 only recommendend.
So what shall I use for my M38

Actually I´ve taken Castrol Classic XL SAE 20W-50 .....

Post by **wesk** » Tue Jul 10, 2012 9:08 pm

Using the search function would get you the 100's of posts on which oil is correct, best and etc.

To cut to the chase the problem is associating which century's jeep engine engineering technology to which century's oil engineering technology. You have an early 1900's engine design with large internal clearances that needed a heavy oil to fill them. Modern jeep engines have much closer clearances and operate at 40 or more degrees hotter coolant temps and are designed to use thinner oils.

Will your 21st century 20w50 oil hurt your engine in the long run? Probably not. Would a quality straight weight 30 or 40 weight oil hurt your engine in the long run? Definately Not.