oil is oil etc. (?)

That little seal you talking about Paul doesn't mean much in itself. It's those letters on the seal that do mean something. You might want to investigate what those letters mean. Generally, if it't new oil in your old truck, it more than meets the requirement. Then again, you'd want to use the oil for a gas engine if that's what you still have in there.

Valvoline is a premium motor oil made from new petroleum stocks. It will work just as well in your '82 as it does in my new Silverado. H

Just make sure to get the highest letter rating and if I remember right it's H. If you find one higher get it. Some of the lower ones can be considered "snake oils" because they can actually hurt your engine. Stay away from brands like quakerstate and penzoil. A study showed them as having some of the highest contaminents. Valcoline is a good brand and I see that's the one you got so good for you.

official

I like to look at the back of the bottle of oil in the $1 store. One brand has a phony looking seal and the words, "MISCIBLE WITH ALL BRANDS OF OIL." That means you could mix it with any brand, but it sounds official. I can't find any Valcoline around my part of the globe.

When I used organic oil, Valvoline was my brand and 10W-40 was on the can. I even tried the Valvoline 'blend' oil, but I didn't see it was worth the $$. Because of the organics in that 'blend', it still must be changed every 3K miles. Change the filter and the oil every 3,000 miles and your engine will do ok.

Years ago I began using Mobil1 syn oil, along with Wix filters. Now I change the Wix filter every 3K miles, top off the crankcase with M1. The filter gets changed every 3K miles and at the fourth filter, I change the oil. Cost-wise it works out about the same, except I don't have to crawl under to change the oil so frequently. The M1 syn oil is better overall than the organic oil, IMO.

Dave S(Texas)

I gave up on those 20/50, 10/40, etc., when I bought my first Mercedes diesel. The recommended oil for a diesel is 15/40 which is a much higher quality oil and made for much more abuse than standard oil blends. Don't know much about the synthetics but they are generally not recommended for diesels. I now use this higher grade oil in all my vehicles, including a '73 ford F-250 (390 engine) and my 1949 Ford tractor. Wouldn't use anything else. Check it out.

The only difference between SAE 20W-50 and SAE 15W-40 is the amount of viscosity modifier added to the mix. SAE viscosity grades have nothing to do with the quality of the oil.

Agree completely about the quality of oil.

And who says that synthetics are not generally recommended for diesels. My daddy's 1992 Dodge Cummins lists oil specs for both standard and synthetic oil!