Now I've heard its bad to go synthetic on old vehicles like my 89 since they were built before the days of synthetics. Is this true? Or could I switch to a high mileage synthetic and be fine?

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Read the link that slick gave you. Syns are newer technology and lube waaaay better. I hate it when people get stuck on old ways of thinking...

 

The reason people have these misconceptions are from when synhetics first came out. They have come a long way since then

 

valvoline max-life 10w30 puralator filter change @ 4k

 

Mobil 1 5w-30 and Pureone purolator filters. Consumer reports gave the pureone filter very high ratings.

bobistheoilguy.com is an excellent site.

Keeping it simple, 10W30, 5W30, and 0W30 all have the same viscosity at operating temp. The start up viscosity is the difference. The higher the number, the longer it takes to lube your engine. 90% of engine wear occurs at start-up.

I go 10,000 between changes. Several studies (independent ones) revealed that mobil 1, and other syns, lasted well past 15,000 miles. Figure in the cost of regular 3,000 mile dino changes and synthetic becomes very affordable.

I love this discussion.

 

So what I'm getting from this. If you had a 1989 renix Cherokee, you'd put synthetic in it? If so, I'm going to have oily fun tomorrow!!!

 

I just run the Castrol 10w30 GTX High Mileage with a Mopar filter. It works fine for me.

 

I got a 1990 (same engine and config as yours) Its got 300k miles on it. I run sythetic mobil 1 on it and a puralator filter. 10w-30. Its served me well so far. Nough said IMO.

 

:-):-):-) says it all

 

Hell YEAH I'd run full synthetic in it. If you find annoying oil leaks after the good stuff cleans your engine up, then start buying gaskets lol instead of complaining about hahaha!

 

Walmart brand filter, and walmart brand 10w 30..........just went over 200,000 miles today, every 7000 miles, its about $15.00 an oil change if I do it myself

 

Damn, that's cheap. I do 3k on conventional, 5k on syn, depending on driving conditions.

 

BAM!!!! hit the nail right on the head. yes synthetic finds all the old seals and will tell you where all your leaks are, but if all the seals are good, then the synthetic, or synblend is actually good for your jeep. mine runs great and i use Valvoline synblend 10w30 with and Mobile 1 filter.

 

And remember, viscosity is viscosity. If it leaks with syn, it would have leaked with rotten dinosaurs.

The ONLY possibility of syn 'causing' a leak is where sludge and gunk get washed away by the new syn. The wear and tolerance changes were already there, syn didn't cause it.

Your engine will thank you for synthetic during those 20 degree cold weather starts. It's just perfect molecules in a bottle. Science. Perfect molecules have come to help the perfect vehicle. (my wife just laughed)

 

Napa gold & castol high mileage 10w-40 since I run her hot & hard...plus its like 100* daily here
Using Castrol syn. on my next oil change, only got high mileage because it was a "deal" or "promotion" they had going on.

I to have heard that with the Napa gold you see an increase in oil pressure..I'm not sure why but my gauge shows an increase after the oil change. Anyone care to speculate on this?