I am the Director of Maintenance for a large trucking co. and go to a lot of different schools and classes on motor oils. so here goes......the heavier the oil the hotter it runs, the lighter oils can run up to 100 degrees cooler. Non detergent oil is designed so the first time the oil gets hot, a paraffin separates from it when the engine cools down, and lays in the bottom of the oil pan. every time you shut down the engine, say overnight the dirt and metal particles fall out of the oil and stick to the paraffin, hence you used to have to take off the oil pan every year and wash out the crud from the bottom of the pan. If your Crosley has an oil filter, then run a multi-weight detergent oil, preferably a 20w-50. Crosley needs a heavy oil to displace wide clearances in the internal engine parts. 20w-50 oil is a 20 weight oil at all times, it's just that when it gets hot it pours at the same rate a straight 50 weight oil would at the same temperature. that gives you cooler running temperatures, with the benefits of a heavy weight oil. An oil filter cannot remove Teflon, because Teflon is in a liquid state when added to the oil, an oil filter will only remove dirt and particles larger than 5 micron.

What type of motor oil to you all use? 30W was original...but....modern technology is here....

I would use 10-30w or if oil pressure was a little low, 20-50w..Regular detergent ..Like Amalie, Valvoline, Pennsoil...Maybe some one has had good results with synthetic? I only use Mobil 1 in lawn and garden tractors [was left over from my pulling tractor in which I think it lost power]but it works good there.

I use 20W-50W Valvoline Racing oil. I find the extra weight at the high end not only gives me better oil pressure but it doesn't seem to leak out those marginal seals and cam cover gaskets as quick. Since I don't get the Crosleys out below about 40 degrees most years the 20W is also not a problem. Jim...

I use the top 10W30s in my two CCs. But you don't have to buy the expensive namebrand oils as long as the label has the SJ seal. Now, the air-cooled Waukesha-built 2-cylinder engines are a different story. I use at least a 50W or preferably a 60W racing oil in my '42 sedan, as the clearances are looser in air-cooled engines to allow for expansion and contraction. I get this oil from good auto-parts stores. And I'll change it more often, because of the extra blow-by and resultant contamination. Incidentally, Waukesha (pronounced WALK-a-shaw) is still in business, but they make only large stationary engines now, for big generators and pumps and the like.