[speeder]

I’m a big fan of putting some ATF or Marvel’s Mystery Oil in the crankcase and taking it on a few hundred mile high speed road trip before changing the oil on old engines. It tends to do a great job cleaning and unsticking the oil control rings, (bottom rings on pistons), but draining it really good and long from the bottom is essential, IMO. If I really suspected sludge or other heavy dirt in the engine, I’d invest in an oil pan gasket and remove the pan as well to inspect.

Sucking the oil out through the top is only ok if it’s always been changed on time or sooner.