Diesel works good. My 79 CJ's 258 was frozen when I first picked it up. I fill it full of diesel and let it sit for about 4 days. Then finally broke it loose. After turning it over by hand for awhile and then by starter I drained some of the nastiest and funky looking junk I have ever seen out of the engine. Fresh oil and filter and she started. Ran it for about 3 weekends and did it over again. Now the oil pressure in my CJ is junk after getting it up and running for awhile it drops to about 5-10 psi. I have a high volume pump to swap into it, just not done it yet.