Have done tons of research and am deciding to go synthetic. It's a 2000 Cherokee with 127k , previous owner said he replaced the oil pan and valve cover gasket. Still has a small leak I'm guessing from the rear main. I have read all over forums that Mobil 1 10-30 full synthetic is the way to go. I don't think it will be a huge deal unless I discover even more leaks in which case I would switch back to dyno oil. What do you guys think? Any suggestions? If you are running synthetic, what brand and when did you switch, any leaks or problems from switching?

 

I like mobil 1.

Synthetic isn't going to stop or slow the leak, tho.

 

I had a leaky rear main on my '98, changed it, ran castrol syntec through it after the seal replacement and the rear main leaked. Changed back to conventional gtx and it didn't leak. Proof enough for me on an older engine. I feel that if you start early on in mileage on a "newer" engine you are fine. Starting synthetic on an engine over 100k miles I wouldn't recommend it, neither would I recommend going to it on an older engine with larger tolerances for wear parts. Just my experience and opinion. By the way, I run syntec in my car for years and nothing leaks. It's a 2000 Grand Prix GTP.

 

I know, im not trying to stop or slow it down. Just really looking for better engine protection.

 

Synthetic oils are higher performing oils, but they have their purpose. They are meant for higher tolerances engines. You are supposed to prolong the oil change intervals, if you are willing to risk it. I change my oil every 5K no matter what oil I use. If you use a high(er) grade conventional oil there should be no difference. Remember oil does a few things, prevent wear, cushion recripricating components, clean the carbon deposits from ignigion. A good oil will have a good additive package or detergent. Oils aren't what they used to be. Castrol, Valvoline, Mobile are good choices. I would stay away from Penzoil, just my .02.

 

I don't plan on going past 3k miles even if it is synthetic. Only reason I'm considering going synthetic is because Wal-Mart has in on sale for $25. I'll probably be going back to conventional after 3k miles. Maybe it'll clean up my engine too.

 

But if it doesn't create any problems like leaks, ticking, or piston slap, would it be safe to stay synthetic? it would still be 10w30.

 

If u r switching to synthetic, why not 0W30 or at least 5W30? Has your research been mostly from reading opinions or reading facts?

http://www.supramania.com/aehaas/

 

Honestly it's been mostly just opinions I read on forums. I was thinking going 5-30 but it's getting warmer where I live so decided with 10-30. I really don't know what's best for my jeep, I've been a Pennzoil guy for years but everyone says to stay away from that.

 

Read the link I post......then u will understand how much more important the 1st number number is. 0W30 and straight 30 r the same vis at operating temp. However, 0W30 will flow quicker to the top of the motor than 5W30 or 10W30 or 30 will flow to the top, at any temp below operating temp. Again, read the link and get motor oil facts, not opinions.

 

In most applications changing oil every 3000 miles is a waste of oil... And perpetuated by oil companies to sell more oil.

 

Very good link to read. No opinions or speculations.

Mobil 1 10w30 is a fine oil.

 

I run Rotella T6 5w40.
Synthetic oil has smaller oil molecules..and can make more fluid leak out then if you were using regular dyno oil.

I wouldn't recommend going from dyno to synthetic for 3k, then back to dyno.
Stick with what you already have, or move to synthetic, and stay there.

 

I don't wanna read all that stuff!

Just tell me what is your opinion of the best oil for a 4.0 with 200000 miles. And without knowing what p.o. used.

 

What salad said.

And djb383 said.

I use 15-40 Rotella T3 in all of mine.