What kind of engine oil do you suggest for a '39 P8 (original flat six)??. The car has an oil filter assembly. I live in Oshawa, Ontario Canada (Love to drive my Plymouth in a GM town!) and the car will only be driven from May to the end of Oct. It is stored indoors during the winter months with a full tank of stabilized fuel and is started, brought up to operating temperature and rolled at least once a month. Thanks.
This topic will probably bring forth many opinions.
My opinion is that modern multi-viscosity motor oils are fine for the old L-head 6 Plymouth motor, especially if the engine has been recently rebuilt.
Some will say that oil with detergent will loosen old gunk and that will lead to early engine failure. Since all multi-viscosity oil has detergent in it, this would leave you with a single weight oil. The problem with single weight oil is that if it has high enough viscosity to provide protection when hot it will be too thick to provide protection during the first few seconds after starting when most of the wear happens.
So my feeling is that if you are worried about gunk in the engine, drop the pan, pull the valve covers and clean it out. You can get almost everything except the galleries that way. If your galleries are full of gunk then you are driving on borrowed time anyway. Once it is as clean as you can get it inside, run modern oil which is far better than the old single viscosity stuff.
Depending on my mood and what is on sale at the local auto supply I run 10w-30, 20w-40 or 20w-50 in my PD engine. Starting with engines later in the 1933 production run and on up through the end of L-head engines the oil pressure relief system shuts off oil to the bypass filter when the pressure is too low. So with engines late-1933 and up you can more safely run the 10w-30 or 10w-40 than I. If it is summer and I have long tours (1 or more hours where I expect 50+ MPH speeds) the idle pressure on my engine with my oil pump mounted oil pressure relief valve running 10w-30 is a bit low for my liking. But your 1939 with its improved oil pressure relief should, with decent bearings and oil pump, have good pressure with the thin stuff.
If my memory is working correctly, I believe there was a lenghty topic on the "Old POC Board" about engine oill.....detergent vs non-detergent...
Some of the postings held that the use of detergent oil in old engines would lead to nothing but ruin and darnation, while others felt that detergent oils were the best thing since sliced bread. I have been using detergent oil in every motorized piece of equipment I have owned since the mid nineteen fiifty's, the only exception being engines that have BABBIT BEARINGS....... I was told a long time ago that detergent oil will erode babbit bearings.
The early versions of multi viscosity oils did not hold up well, they tended to break down very quickly, then you only had 10 or 20 w oil which went right through the engine, I had this problem with the 48 Merc engine in my 36 Ford in 1954, however when I switched to Union Oil "Royal Triton" I never had any more problems . I have used Castrol 10/40 or 20/50 for over thirty years with no problems.
Most people are not aware just how important oil is to an engine. In reality, an engine only needs about one quart of oil for lubrication, the balance of the oil is one of the main sources of cooling for the engine. Modern multi-viscosity oils are designed to "hold onto heated surfaces" then carry the heat away where it can be cooled in the pan.
An interesting test/demonstration is to use an electric hot plate which is set at a medium/high tempreture. Drop some non-detergent oil (MS) on the heated plate, it will go up in smoke, as you move through the various grades of oil you will see them "go up in smoke and/or run from the heat", SE/SF grade oils will just sit on the hot plate.....Bill
Dear Fine,
for Engines without full flow oil filters, a highly detergent oil seems not best. It keeps some of the dirt particles floating in the oil, they will not be filtered out in every oil round and are fed back to the Babbitt bearings, causing heavier wear than on full flow oil filter engines.
So, following my informations, it may be better to let dirt particles sedimentate to the oil pan rather then keeping them floating round per round.
On our annual oldtimer car fair I found Millers Oils Company. They offer a wide range of Classic oil specialities for old engines. They recommended me a low detergent oil for my recently rebuilt P23 engine with the original layout shunt oil Filter System (vs. full flow). I compensate the dirt particles circulation by changing the oil and to cleaning up the pan every year. Anyhow oil should be changed once a year on our beauties.
Seems as millers oil have experienced advice for every oldtimer engine configuration, see
http://www.millersoils.co.uk
Their prices are higher than for mass oils, but I think it is worth it!
Good luck! Go.
It is interesting to note that this very same topic is being beat to death over on the Early Ford V8 Forum (EFV8) . You would think that the contributors to the topic have just changed there names. The common censensous seems to be...... don't confuse me with facts, I already have my mind made up. It is very true that in the good ole days single weight 30/40 oil in the summer was the norm, whereas 10w mixed with karosene was recommended in the winter months. Ask your self.... how many of those old cars ever saw 40,000 miles before they needed rebuilding? If a rebuild was in order it could be done for less than $100. Now we are dealing with engines that cost in excess of $4,000. to rebuild, after spending that kind of money I am going to use the best of everything to protect my investment and insure I don't have to have my car hauled home on the hook....Bill
I am sure MOPAR engineers recommended the use of the best available lubricants contemporary to the vehicles they were producing. Since engine oil has done nothing over the years but improve in lubricating properties, anti foaming properties, viscosity stabilizaton, and usefull life, seems to me they would recommend the best available were they to make a new version of the venerable flathead powerplant today.
Currently using 10W-40 Valvoline in a rebuilt p28 engine. 2500 miles, no problems. idles at 25/30lbs, shows 45/50lbs at driving speed. Thinking of changing to synthetic at next change.
I rebuilt my 57's flattie a few years back. I have used 10-30 Mobil synthetic exclusively since break-in. I have had no problems with the synthetic. I pulled the tappet covers to reset the lash and the engine is spotless inside. The motor has about 15K on it.
A possible option is Penrite oils (an Australian company). I use their (lightly detergent) engine oil in my '31 Buick 8-57, and their tranny lube too---because I couldn't find what I wanted any where else in reasonably small quantities. My old 8 banger sounds like a new engine. It is specially designed for old engines and for a wide range in temperature. You might want to check it out.
http://www.penrite.com Check on lubes for pre-1970 cars, especially their "Shelsley" oil.
If your car is a daily driver and you put a good number of miles on it, Penrite stuff may be a bit pricey. But if it's a show car and you don't put over about 1k miles on it in a year (read: change the oil and filter once or twice a year), it may make sense for you.