The advice about not using detergent oil in stovebolt engines went out of date before most of the members of this forum were born. The only thing running a ND oil will do is assure that all the dirt particles too small for the filter to strain out will get deposited somewhere inside the engine as sludge.
A full flow filter has to have filter media with pores big enough to allow enough oil to flow through it NOT to drop oil pressure below safe limits. It has to allow all the output of the oil pump to pass through the filter before getting to the bearings. One engineer I knew used to say "A full flow filter is for rocks, marbles, and other big chunks!" A bypass filter can be much more restrictive, resulting in more effective filtration, because it simply dumps the filtered oil back into the oil pan. For the best engine protection, an engine should really have both types of filters, like a lot of the over-the-road diesels do. The Frantz filter can trap particles down to 2/10 micron, or 0.0002 inches. Obviously, it must be used as a bypass filter.
Detergent oil traps and holds dirt particles in suspension that are small enough to pass through the lubrication system without doing any damage, and they are drained out at every oil change. Using ATF as a "cleaner" is a really bad idea, as it has various friction enhancers in it that should NEVER be run in an engine's lubrication system.
Jerry
