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what oil to use in a 39 120

Posted: Wed Jul 26, 2017 1:43 pm
by dak955
Hello. I am looking at possibly purchasing a 1939 120 sedan with 61,000 original miles. My question is what oil would be best to use based on a few known facts. There is no information regarding if the engine has ever been apart or what type of oil was used in the past. (I am dealing with the widow of the gentleman who owned the car and she has no knowledge of anything about the car. No files, receipts, etc.) There are no real visible external signs that the engine has been apart and the car overall looks like a realistic 61,000 mile car. There is no oil filter on the engine. No oil change stickers on the car. The few oil cans in the garage are different type and viscosity so I can't tell if any were related to the car. The car was driven about a year ago and started a few times since. Since the car appears to never have had an oil filter, am I safe in using a non-detergent oil or should I go a different route? Thanks for the help.

Re: what oil to use in a 39 120

Posted: Wed Jul 26, 2017 4:13 pm
by Dave Czirr
Given the absence of past history, I strongly recommend dropping the oil pan and cleaning it and the oil pump intake screen. The you should be able to ennoy the benefits of a modern multigrade detergent oil.

Re: what oil to use in a 39 120

Posted: Wed Jul 26, 2017 5:49 pm
by dak955
Thanks Dave. A couple of questions regarding your response. Would I only have to clean the pan and the pickup or will it be necessary to do some type of flush in case any other particles / sludge did not fall into the pan? If I get everything cleaned up as needed, what viscosity oil would be a good choice? Thanks.

Re: what oil to use in a 39 120

Posted: Thu Jul 27, 2017 4:49 am
by Dave Czirr
Of course any cleaning you do further to just the oil pan and oil pump screen will be beneficial if the rest of the engine isn't particularly clean. You might consider pulling the valve covers and seeing what you find there. I believe you noted you were in Ohio so your temperatures won't be much different than mine during the driving season, If your engine is pretty tight (without excessive wear) and hold good oil pressure I'd probably start out with a 10-30. But regardless of the oil choice, I'd view my first oil refill as a flush and change it after not too many miles.