I am not sure why you would deviate from the viscosity specified by the people that designed the engine. Many moons ago, it was common to use a slightly thicker oil on vehicles that were burning oil due to worn rings.

Some people use 5w30 or 10w30.

How many miles does it have on it? Is it smoking it burning oil? Are there unusual noises?

Discussing brand is irrelevant because everybody has their favorite brand with everyone claiming they have absolute proof that theirs is the best.

 

I want to switch oils to be thicker because for one i am one of the people that loses a quart or 2 between oil changes which i change every 5000 miles. I have 167,600 miles on it currently and no noticeable leaks. Besides my rear axle seals. I thought about doing the 10w30 if anything but would like to use the same oil on all my vehicles. Unless this 15w40 diesel oil seems to extreme.

 

I am not sure what is gained by using the same oil in a motorcycle as an automobile but whatever. To be honest I am more questioning your use of that oil in a motorcycle than I am in your Jeep.

Have a look at your timing cover. Many people such as me experienced problems with the oil shaping through the cheap porous metal of the timing cover. I had a 2007 before I traded it in on my 2014.

I started out having to add one quart of oil ever 500 miles but it progressed to one quart every 250 miles. Every time I would fill up with gas I would check the oil and most of the time would add a quart.

 

If you put that molasses diesel oil in it, you may do some damage. Which that said, a lot of people had issues with their 3.8s wearing prematurely and burning oil. One of the more popular theories is that Chrysler originally designed this engine to run on 10w30 (designed in 1988, first put into production in 3.8 form in late 1990) . The eventual switch to 5w20 was in an effort to meet CAFE standards, but wasn’t the best suit for the engine. Sometimes manufacturers don’t have the vehicle’s and/or customer’s best interests in mind. If something meets requirements and is “good enough”, they’ll go with it.

 

Chrysler originally designed this engine to run on 10w30 (designed in 1988, first put into production in 3.8 form in late 1990) . The eventual switch to 5w20 was in an effort to meet CAFE standards, but wasn’t the best suit for the engine. Sometimes manufacturers don’t have the vehicle’s and/or customer’s best interests in mind. If something meets requirements and is “good enough”, they’ll go with it.

Yes, exactly, full synthetic 10w30

 

If you live in the snow belt 5w-30 is fine.In the sunbelt (no snow) a 10w-30 would be fine.Even 10w is good to 0 degrees F.The 3.8 isnt picky like maybe a turbo motor would be.