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EFV-8 Club Forum / General Ford Discussion / Best Motor Oil for 35/36 Flathead

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Posted By Discussion Topic: Best Motor Oil for 35/36 Flathead     36fordor 06-22-2018 @ 5:14 AM reply profile send p.m. Member Posts: 78 Joined: Oct 2009 Any consensus on best motor oil, including grade & specific brand, for 35/36 flathead? My flathead guru/mechanic, ole timer, doesn’t believe detergent oils should be used. DD931 06-22-2018 @ 6:41 AM reply profile send p.m. Member Posts: 66 Joined: Nov 2014 Your guru is living in the dark ages. From my perspective you should be using a modern oil. New engines are much more demanding than our old flatheads and lubricating oil technology has moved ahead with those designs. I have a '48 F-1. Its owners manual recommends using "Heavy Duty Motor Oil" stating "The heavy duty motor oils contain detergent compounds and tend to hold in suspension the foreign contaminants which normally would deposit on the engine parts." It goes on to say "This term shall be used to designate an oil having proved oxidation stability, bearing corrosion preventive properties, and detergent dispersive characteristics. Oils of this type are generally suitable for use in both high speed Diesel and gasoline engines under heavy-duty service conditions." Detergent oils were just coming on the market at this time and were considered in the high end of the market. Now, of course, all regular oils are detergent. Detergents in the oil prevent the formation of sludge, which I consider highly desirable. If you pull the dipstick on a modern engine the oil will not show any sludge formation. Wouldn't you like your flathead to be like that, too? Mine is! I use 20W-50 viscosity. Others will have different opinions, but don't fall into the single viscosity trap. Again, following the above logic, modern multi-viscosity oils maintain the desired viscosity over a wide range of temperatures. These were not available in the old days. Then there's the Zinc trap that old-time "gurus" fall into. This has been the subject of much heated discussion. In my opinion there is enough zinc and similar additives in modern oils to keep your flathead happy. JMHO. TomO 06-22-2018 @ 7:41 AM reply profile send p.m. Senior Posts: 7257 Joined: Oct 2009 You will get many opinions based on rumors and other biases, but DD931 said it all. Buy any good oil, drive the car at least 30 minutes every time you start it and you will not build up sludge in the engine. I use 10W-30 in my cars and lose about 1 quart every 600 miles. I believe that the thinner oil helps the engine run cooler. It is also closer to the original specifications for my flathead (30W in summer). The second number in the viscosity is the effective weight (viscosity) of the oil at operating temperatures. Tom carcrazy 06-22-2018 @ 12:03 PM reply profile send p.m. Senior Posts: 1676 Joined: Oct 2009 If you ask 100 people what is the best oil to use in an old car you will get 100 different recommendations. Here is what I use in my Flathead powered cars: Pennzoil SAE 30 Detergent Motor Oil with 8 oz. of Red Line Engine Oil Break-In Additive. This additive is the only one I know of that has the required amounts of ZDDP (Zinc, Phosphorus, and Sulphur) to minimize wear caused by the sliding friction between the camshaft lobes and the tappets and fuel pump pushrod. My reasons for using a straight 30 weight detergent oil is that less viscous oils in my early engines leak past the rear mainbearing. Detergent oils will help to reduce the build up sludge by keeping the contaminants in solution where they can either be filtered out or drained out when you change the oil. kirkstad 06-23-2018 @ 7:48 AM reply profile send p.m. New Member Posts: 192 Joined: Jul 2017 I use valvoline SAE40 detergent do to the high mileage on my 36,but when I first got my car I dropped the oil pan, and cleaned out any accumulated sludge build up,of which I had a fair amount. I didn't what the detergent oil to loosen it and send it through the engine.A rebuilt engine would not have that problem. 1934 Ford 06-25-2018 @ 10:43 AM reply profile send p.m. Senior Posts: 577 Joined: Oct 2009 In my old cars i use 20/50 detergent oil. Good year round oil that is thick enough to leak slower than lower viscosity oils. Usually my engines are not brand new high pressure models. 1934 Ford's since 1972 GK1918 06-26-2018 @ 3:44 AM reply profile send p.m. New Member Posts: 128 Joined: Aug 2016 20 - 50 Valvoline racing oil from Napa the grey bottle....I see recently a new yellow sticker zink label.. FrankM-RG5 06-26-2018 @ 3:09 PM reply profile send p.m. New Member Posts: 135 Joined: Oct 2009 I ran Mobil 1 10w-30 in an 8BA 8100 miles and sent in an oil sample and they told me to try 9000 next time. I believe any modern quality oil will be adequate or more than adequate for your engine. BTW I used less than half a quart on the whole trip.

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