Interesting about those 5.7s and 6.2s. I have had both and because I have decades at wrenching I knew to run Delo 15-40 and both ran outstanding. Most people ran plain gas motor oil in the 5.7 and some still do it in other diesels and they trash the engine as the gas oil is NOT formulated to handle the high combustion temps of the diesel. BTW, the 5.7 was NOT a gas conversion as many believe with differnt heads.. The only thing it shared was the same bore and stroke as the 350 Olds gas engine. It was a totally different block, it said on the side 350D not X or other letters. Had different heads, different pistons and cam and no distributor but an injector pump which is the same as the 6.2 and 6.5. My friend is a retired diesel mechanic. I have a friend at church thats a diesel machanic and good one at that. Wrong oil will crystalize when it gets too hot and then not liquid. The rest is easy to figure out. Its not the weight in oil thats so important but the TEMP which it can handle along with ash or soot control. Change it like any other rig. 3K the most and it will run a long time. Texas Refinery Moly oil can go 20k or more if you change the filter evry 4-5K and replace that quart with the same stuff. But use either the one I recommended or Chevron Delo 15-40 or Shell Rotella T 15-40. I think you idea is smart. A balanced 6.2 with the injectors for the J series will run quite well and get good mileage. There are performance injectors for them also. Don't turbo it unless you run only 4 lbs of boost. The heads don't take to the turbo too well otherwise they run very well. The 6.5s had different heads and could handle them. I had a 6.2L in my Surburban Silverado and should not have sold it last year. It was in MINT condition. It was an 88 with rear a/c and everything worked including the 4 wheel drive. Check out
www.lovercraftbiofuels.com. Its not bio diesel they sell but kits to convert even large engines to run on salad oil from United Grocers, Costco or wherever you get it in bulk and NO additives needed with their kit. For a used engine I would recommend from experience Texas Refinery Moly Pro Spec III. I use it in my rig and in the Burb I had and it makes them run super quiet and stops almost all wear. Thats why I use it. Also gets top higher RPMS faster and faster cold starts. They've been around since about 1921. Long time. Unfortunately most folks did not know how to care for a diesel properly. I have owned several diesels and love them. Just 10 cents of info and I hope this helps you and others out. There is an aquaintance of mine that has one in a full size blazer and gets 30 hwy with it. About 24 city. Has 33" tires and 3.73 gears. A little tall on the tires. I would run 31's the most. His is turboed. Check out hydrogentap.com and hydrogen boost on the net. You can run diesels on it or at least boost it and gets more power and more mpgs. H.
