Standard vs Synthetic oil

[Chryco Psycho]

Most diesel oils have S? ratings on them though

[JCWCuda]

When i was Fleet Mechanic we Used the 15w-40 Rotella in everything diesel or gas and most of my Gas Engines had at least 200,000 miles on them. As metioned before what is most important is to maintain Change intervals and keep Carbs adjusted. One of the biggest killers of Oil is getting contaminated with excess Gas, That is why Fuel injected cars seem to obtain higher milage ,not as much gas washining down the oil

[dimples]

All diesel oils I have seen are rated for gas engines too.

I had a 94 318 Dakota in for a engine rebuild, a couple years ago, with 200,000 miles on it. He has changed the PENZOIL in it like clockwork, every 3000 miles.
There was between 1/4", and 1/2" of sludge in the valley, pan, and the top of the heads.valve covers..........but yet it ran 200,000 miles. It is amazing what we can do to these things, and yet they live.
My 95, has 212,000 miles, on a 318. It idles and plows more than it runs down the road, and is towing when it is running down the road.
The inside is darn near squeaky clean. Amsoil and royal purple are to blame, I guess.............Keep it changed, and they live forever.
in extremes though, synthetic is hands down superior, but the truth is, you could probably run 200,000 miles on wesson, if it was changed often....