Topic: Synthetic Oil

[BlackYJ]

I took a look at the page in the FAQ page about GL-3 and GL-5, but I was hoping to get some first hand experience with synthetics

I have never ran synthetics, but I am looking to change over to them in my engine and my tranny.  I live up here in Alberta, so I don't have access to all the same oils you guys do in the US.

So for the engine, 4.0L (i know this is a 4 banger site, but I did have a 4 banger for a long time), what is the recommendation?  I had seen the usuals, like Mobil 1, I can also get Royal Purple and Amsoil.  I will be running 5w30

For the tranny, AX-15?  Again not a lot of choices, RP is available and then your usuals like Quaker State, Pennzoil, etc.  Looking for a 75 or 80w90 GL-5.

Thanks in advance

[lanulos89]

if you have a sorta high millage jeep, and have been running non synthetic, keep it that way IMO.  All my experience with switching over to synthetics, it make the engine start to leak and stuff, now synthetic tranny fluid i have no idea about.

[superman1456]

here is a great test put on by hesco about a special synthetic oil i hope this helps you with what you lookin for good luck
http://jeepers.biz/forum/forum_posts.asp?TID=82&PN=1

[chardrc]

we use mobile 1 on our 97 and 06 4liter motors.. but not on my 2.5l because of its oil leaking problem

[chrisfranklin]

I use synthetic oil in my Jeep - actually 0W20 Mobil, currently - and like it very well (actually had to buy this "0" Weight oil by mail).  I've used other weights of Mobil/Castrol synthetic (5w30, 10w30, 10w40) in my Jeep and two other vehicles (two Fords), all with no problems, even when vehicles had higher miles.  

However, have also seen a vehicle's oil pan gasket leak after somebody changed from regular to synthetic oil.  I guess I risked leaks in mine when I switched, but actually didn't seem to have a problem after I did.  

I'd probably give the Amsoil or Royal Purple a go myself, too.  
Think those can be had in 5w30.  

Think if you have a higher mileage jeep there is going to be a higher risk of gasket problems and leaks if you switch from regular to synthetic engine oil; however, I think that an oil leak in such a situation is not necessarily certain - actually the risk, overall, may be quite low.

Use the Mobil Synthetic transmission fluid, too.  Haven't changed it in 4 years, so probably around time I do - but, it has lasted/worked well.  Have heard good things about the Redline synth transmission fluid and their MT-90 product.

[Jesse-James]

I just switched in mine. (95 with about 94K) Put in Mobil 1 10W30 and after about 2 weeks of driving it, I've noticed a lot less lifter noise at startup. Glad I switched.

[BlackYJ]

I know there is a myth about switching ot synthetic and it starting to leak, by why, there are both still the same weight and viscosities, synthetic is not thinner.

My engine has about 210,000 km on it and I am getting some noise in the valve train.  I guess my reason for switching is just to help the engine out more.  I burn a little oil, but nothing major.