Detergent Oil or Non-Detergent?

[Bobs_AA]

Originally I believe the engines used non-detergent oil, because they had no oil filters, in hopes that the dirt would settle out? Correct or not?
Should non-detergent still be used if no after market filter was added?
Your thoughts and recomendations.
Thanks in advance.

[E.Moore]

Yes, you are correct that non detergent oil allows dirt to settle to the bottom of the oil pan after the engine is cut off and the oil cools down. There is always turbulence at the oil pick up when the engine is restarted and the oil becomes hot and some of the dirt returns to the oil flow every time the engine is run.

The old non detergent oil had and still has practically no additives to protect internal combustion moving parts from wear, particularly when the engine is first started.

It was the only lubricant that was available. After WW2 the development of high compression & high horsepower engines required additives to keep the camshaft & lifters from quickly wearing out. Valve springs had become much larger and the greater tension of the valve springs against rocker arms and lifters against cam lobes had to be protected with anti wear additives. Detergents were added to cut down on sludge formation.

The American Petroleum Institute placed performance designations on the different grades of oil, starting with SA for non detergent oil used in engines prior to 1930.

SM is the current API designation, which contains no zinc or phosphates, that used to protect against rapid wear of the cam & lifters. Use of current motor oil will cause your flat tappet Model A / AA engine, or any flat tappet engine up to 1992 to wear out quickly.

Engine manufacturers had very high warranty returns of O2 sensors and Catalytic converters, causing check engine lights to come on. Auto Manufacturers lost millions of dollars in Lemon Law arbitration buy backs due to the repeated comebacks of the check engine light, due to zinc & phosphate coating the O2 sensors and Catalytic converters, and had the oil manufacturers eliminate the zinc & phosphate to rectify the issue. As a result, roller tappet lifters were and are currently the answer to that problem.

Oil used in the Model A / AA should have an API designation of SJ or earlier. Diesel oil carries API SJ & SM. I asked a SHell oil engineer how the diesel oil can carry both designations, and he said that a synthetic replacement of the zinc & phosphate is being used to prevent rapid wear of the cam & lifters in flat tapped engines.

I always add a small bottle of break in lubricant to my oil change of Shell Rotello 15/40 or 10/30 Diesel oil and I don't have to worry whether there is enough anti wear protection. The break in lubricant is full of zinc & phosphate and will add the high levels of both to the oil change.

Proceed at your own risk when it comes to modern oil in antique engines.

Three pages of useful API information at http://www.burkeoil.com/pdf/oilguide.pdf

[30TownSedan]

I have always used nothing but non-detergent.

[tiredtruckrestorer]

I also agree that a good diesel oil is the way to go. I always use this in a new engine. In an older engine though, the detergent can pickup dirt and circulate it throughout the engine. Unless I remove the pan and throughly clean it and the valve chamber out, I just use a non-detergent oil with an additive like Lucas to add the wear protection back.

Keith

[fordman88]

i love rotela 15/40 ut was affraid ir mite be to thick. im guessing this is not the case then. also was wondering if anyone has ever ran a engine flush through right before changing their oil. i wanted to do that to make sure there wasnt any gunk hiding anywhere but didnt wana do any harm in the prosses.

[E.Moore]

I've used engine flush before and stirred up more than it was worth. The engine flush can cause loosened sludge to stop up the oil pump screen, resulting in a real mess, and the problem would be that it is discovered too late.