I use low cost 10W_30. I used to use Quaker State and Pennzoil, when they were low cost, but they got expensive (same stuff, higher price, probably) , so now I use Walmart 10W-30. I have 368,000 miles on my 1985 V8 305, so the cheap oil must be OK. I always change the oil and filter every 2 to 4 thousand miles.