I just bought a 94 cherokee sport and did an oil change with Valvoline MaxLife synthetic b/c my xj has almost 250k on the engine. I recently heard though that running synthetic in older engines is not a good idea and that I should run regular oil. I'd like to hear peoples input on this.

 

The synthetic will cause old seals to leak, but the way i see it, they were going bad anyway. I ran synthetic in my 90 because i got the oil for free. After awhile it started leaking and all the seals i changed were brittle/rotting and pretty much shot anyway. There are a lot of different thoughts about synthetic but i don't think there is anything wrong with it as long as your engine is well maintained.

 

Most of my seals are newer anyways b/c they were replaced before I bought it. So if thats the only negative about synthetic then I think I'll stick with it.

 

That's the only thing i've seen personally, there are a lot of people who swear by diesel oil for the 4.0s also. Just do your research before you commit to anything. The synthetic may not be worth the cost in these old engines. There are tons of posts about oil in the forum.

 

Alright, thanks man. I guess I'll just keep gathering info till I come to what I think is an educated decision.

 

Yeah its tough to find good facts about it, i just tried to read up enough to be able to form my own opinion and make sure i wasn't going to destroy my motor. IMO synthetic oil isn't worth the cost in engines that weren't designed for it, but that's just me.

 

You make a pretty valid point there. It makes complete logical sense. It was good enough to convince me to use regular oil from now on. Thanks again for your help. Now I just got to figure which brand is the best for my engine.

 

Synthetic oil doesnt cause leakes. synthetic cleans so much better it cleans all the gook and junk that was hiding any leaks may start. Good synthetic oils have conditioners to help with that by conditioning seals to help prevent that. If it leaks you had a leak to start with, sludge was keeping it from leaking.
I swapped my 88 over and it was very neglected i swapped over to Synthetic and i have no leakes.
I swapped a freinds 90 something mustang over to Amsoil as well and he had a small leak that Stopped.
I have 237k on a 97 4 runner no leaks.

 

http://www.firstfives.org/faq/oil/oilartcl.html

 

vavoline maxlife is a synthetic blend of reg and synthetic oil my good friend read about oils on the web until he got so much info. just bought 2nd xj in july 2000 with 102k on it this what he recommened to me because it conditions the seals the engine seems to like it so I am going to stay with it by the way check your oil every so often withitin yours you might be surprized how long it stays clean you might be able to 4000 miles between oil changes but do YOUR research and decide for yourself just my 2cents

 

You did it right man! I did that before and now my 94 cherokee sport is better than before.

 

I've always used mobile 1 synthetic with no problems. Never had a leak in any of the cars. My old 93 toyota Camry had almost 300,000 miles and ran like a champ until I sold it and the new owner crashed it.

 

technically speaking the only benefit of synthetic oil is that it has a longer useful life under both normal and severe conditions - it does not break down as quickly as dino oil. The same additives and conditioners you can find in synthetic oils you can also find in dino oils.

IMO it's not worth it as much in older vehicles. The older the vehicle, the more quickly the oil gets dirty in my experience. I would rather change my oil more frequently to remove that crap then to let it circulate for 10,000+ miles just because the oil is good for it. It may be cost effective for newer engines that are designed for extended service intervals (10k to 15k)to use synthetic oil, but not really for our engines which have a service interval of 6k to 7.5k. It simply is not worth the cost to throwing away oil that is only half way through it's usable life.

If you do like the idea of synthetic oil i recommend a synthetic blend - which combines the best of both worlds - lower cost with extended service life.

What is more important is the cold weight and viscosity. a 0w or 5w oil will make startups easier, but reach the same viscosity at operating temp. ["5w-30" = "cold weight-viscosity"]
The lower the viscosity number, the more easily it flows (note-you don't want to make it TOO low or you won't build enough pressure)

Just my 0.02

 

I just love how everyone becomes an expert in oil, try going with real tests and real eingneers that test oils.

 

you mean like this: http://www.bobistheoilguy.com/cms/in...d=84&Itemid=92