Hey guys, just got back from getting my 3rd oil change in my 2011. I've got 15k on it, and have been getting changes every 5k with tires rotation too. Anyway, the first two times I went to the dealer, and they had no problem putting full synthetic 5w-30 Mobil1 in it.

I took it to a closer, local mechanic today, and he went on and on and on, about he wouldn't put that weight in my Jeep, b/c the manufacture's spec was 5w-20. Finally, I convinced him it was ok, but later, its kinda gotten me thinking. Am I hurting the engine by putting 5w-30 in it?

Seems kinda ridiculous to me, but was he right? Thanks.

 

No harm done.

 

No harm here, I put 10w-30 and 5w-30 in mine before when I couldn't find 5w-20.

 

Possibly the 20W spec by Chrysler helps their Corporate Fuel Economy just a little?

Seems strange to run 20W in hot weather.

 

There are lots of opinions that a 30+ weight is OK in you engine. Don't see any signs that it’s bad so I guess it must be OK, right? Chrysler recommends 5w20 because they’re trying to get better numbers to make the EPA happy. Etc.

So far I haven’t seen anyone show actual oil analysis on their engine using 5w20 then 5w30 then maybe back to the 5w20 and then the 5w30 showing no additional/less wear. Which is better?

If you want to experiment with different weights of oil you may want to analyze you oil with a 5w20 then shift to 5w30 and see what the oil analysis reports, or just get an analysis after running 5w30 and if all of the numbers look good then it really is OK, or stick with the opinions and say your Jeep runs fine with a 5w30...

 

30K on my 2007 JKU using mobil 1 synthetic 5w30 and haven't had any problems. No knocking, no oil consumption, nothing out of the ordinary. Just one happy Jeep

 

What's the advantage of using 5w-30

 

Thicker oil. Safer on hot jeep engines. Makes sense because of the thin cylinder walls. It is after all a maxed out 3.3. My concern is blow by on thin walls. 30 weight would help to alleviate this IMO.

 

Not to hijack but what about in the winter, any issues with 10w30 in the colder climates w/the 3.8? Gonna be changing the oil this weekend before the cold arrives...

 

I would use 5W-something in the winter. The lower "W"inter viscosity oil will get moving quicker on cold starts.