my religion is better than yours: Mobil1 oil zinc

Yeh, if you have ever inspected an old cam that survived the engine wearing out on mileage you will see the taper still on part of the small diameter of the lobes and the top of the lobes worn completely to match the lifter.

the earth really is flat, but only when you turn your back and no one's looking. PROVE ME WRONG.

"You can't mix conventional and synthetic or your engine will explode."

"You can't break an engine in on synthetic or it'll explode."

"You can't mix oils of different viscosity or your engine will explode."

...I broke my 258 in on a mixture of every random partial quart of oil I had sitting on the shelf in my garage. There was conventional, synthetic, Pennzoil, Castrol, Havoline, Valvoline, 5W30, 5W50, 10W30, 10W40....all mixed in there, plus a bottle of ZDDP additive. I broke it in and drove it the first 800 miles on that. It runs perfectly. It leaks from nowhere. It did not explode. Why put good oil in an engine that is breaking in? It's going to make a ton of little metal shavings no matter what and you'll be changing the oil soon anyway. Put cheap stuff in it. Great opportunity to burn up all those random quarts sitting on the shelf since 2003.

I've also put synthetic into old sludged up high mileage engines and run them for thousands of miles. No worse leaks, no oil screen clogging, no explosion, supernova, death, or armaggeddon. They just ran...as they always have...and were still gunky when I decided to rebuild them for the fun of it. No squeaky clean engine inside. I still had to boil them out and do a lot of scraping.

FSJunkie wrote: "explode."

The older engines at least in stock or mostly stock form are simply so low stress than most any oil of the proper viscosity containing enough extreme pressure additives will work as well as any other oil. It's the kind of thing where once you pass "good enough", anything better is simply overkill that results in little if any benefit. It's just a comfort margin.

Run $12 AMSOIL if you want. I don't think the engine will last significantly longer than it would on $4 Walmart oil.

Think about how many 20 year old Jeeps with 200,000+ miles on them are sill on the road out there with 4.0L's filled with cheap generic conventional oil and yet are not frying camshafts left and right. The 4.0L is more highly stressed than just about any other stock AMC engine.

You have to admit that these engines originally ran for many, many miles on the oil avaliable back in the days when they were new. I try to find modern oils that closely resemble the ye olde oils of yore. Old engines call for old oils. Oils designed specifically for those engines and engines designed specifically for those oils. That is why I like Rotella T and Penngrade1. Rotella is Diesel oil, but I believe an AMC 258 has more in common with a Cummins than a new Acura, and the oil should reflect the engine.