What Engine Oil do you Recommend !

[John Lynn]

Hi

I have a 1920 Oakland 34C Cabriolet Roadster running a six cylinder engine.

Would be interested in your comments on what is the best oil type / grade to put into the vehicle. I have had a lot of conflicting " advice ". Some some a heavy grade and other say lighter grade. 

Thoughts please

[TerryB]

Do you know when the last time the engine was rebuilt?  That can help in giving you an answer.  Most old cars used heavier oil as the manufacturing tolerances were a lot bigger than they are in newer designs.

[JFranklin]

Please both opinions and use a multi-viscosity oil, 10-40 or 20-40. All oils today are better than what grandpa was using.

[Spinneyhill]

What is the history of the car? Has it been used much or sat for years? Has the engine done a lot or a few miles since rebuild?

 

The usual advice is to remove the sump and clean it out. It may be full of sludge and dirt. If it hasn't run in a long while, the engine could be dirty inside due to the lower quality oil way back when.

 

Use a multi-grade with the lowest first number (before the W) in the viscosity you choose, For example, 5W-40. The 5 indicates the oil behaviour when cold and indicates it will be able to be pumped and splashed around like an oil in the SAE 5 band. This allows for oiling quickly after cold start so reducing wear. The second number is the SAE viscosity band when it is hot. Personally I would use a 5W-30 if the engine is low miles or a 5W-40 if higher in miles.

 

Is there a recommendation for oil in the handbook? There are approximate correlations for oil descriptions and SAE grade, which were first published about 1924.

 

 

Edited September 24, 2018 by Spinneyhill (see edit history)

[John Lynn]

Engine was rebuilt / reconditioned approx 10 years ago but not run until  3 years ago when it was fully restored and road worthy. Has had very low use.

I now use it on a regular basis for rally runs and general use ( most weekends ). Does not burn any oil and runs really well. Originally had 25W/70 oil used by previous owner but have been advised that 20/40 is ok.

[ng8264723]

Somethings with zinc!

[Spinneyhill]

Rather than 20W-40, go to a 5W-40. There will be far less wear on startup because thinner oil moves more easily that thick oil, so you will have earlier full lubrication with 5W than 20W.

 

Of course, your car is years ahead of zinc in oil for flat tappets. However, you can seek the maximum benefit available using a diesel oil of API rating CI-4 (or CJ-4).

 

Please read Richard Widman's paper at http://www.widman.biz/Corvair/English/Links/Oil.html. You will learn a lot about viscosity and zinc.

[JFranklin]

Your car (1920's,) was built with much looser tolerances than a modern car that uses thin oils. I wouldn't use anything less than 10-30 oil

[Spinneyhill]

7 hours ago, JFranklin said:

I wouldn't use anything less than 10-30 oil

The point is, when an oil is cold it behaves as a much higher viscosity. See the graphs in Widman's paper. An SAE 30 oil might have a viscosity 10 or 20 times the SAE 30 rating at cold start. A 5W oil will have a viscosity that is much closer to SAE 30 at cold start. Remember viscosity falls markedly as an oil warms. For example, here is a graph from Widman's paper. Notice that the SAE 10W-30 has a viscosity when cold of about half that of an SAE 30 oil. Notice also the very high viscosity of the 20W-50 oil when cold; it will be hard to pump around or to get to splash bearings etc. adequately. A 5W-30 oil will behave as an even lower viscosity oil when cold, but not below SAE 30.

[JFranklin]

From your chart I would choose SAE 10-30. When the car was new it used an oil close of 30 wt or 20 wt. You certainly want a cushion effect from oil when starting a cold engine. At 120 degrees F they all are acting at approximately the same viscosity. The bearing surfaces, if real close, needs an oil that can be introduced into the tight tolerances thus modern 5-30 & 0-30 oils. Any oil today is better than when the car was new.

Edited September 26, 2018 by JFranklin (see edit history)

[MikeMike]

On 9/24/2018 at 2:46 AM, John Lynn said:

Hi

I have a 1920 Oakland 34C Cabriolet Roadster running a six cylinder engine.

Would be interested in your comments on what is the best oil type / grade to put into the vehicle. I have had a lot of conflicting " advice ". Some some a heavy grade and other say lighter grade. 

Thoughts please

 

Lower viscosity = higher flow rate.

Lower oil pressure = higher flow rate.

Higher flow rate = better lubrication. 

 

Better still, ask, say Castrol, what oil they recommend.

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