Oil for the Model T Ford

What kind of Oil does a Model T use?

When Ford started building the 1909 Model T in the fall of 1908 there were not oil grades such as we have become familiar with today. The Society of Automobile Engineers (SAE) which was formed in 1905 did not identify oil grades for several years. The industry standards for motor oil were far different from what we have today. There were oils designed for motor car “cylinder use” in other words, oil to use in the crank case. These types of oils were available in three (or more depending on the oil company) basic grades known simply as “Light”, “Medium” and “Heavy”. Here is an excerpt from a Model T service manual that was very popular at the time known as the Dykes Manual:

So we know now that Ford specified the oil grade as “Light”. But what does that mean exactly? How do we know what “Light” oil is when looking at the oil available in the auto part store or Wal Mart?

The guys who collect oil cans know the answer, because there was a period of time in the 1930’s – 1940’s when oil cans were marked with both the old “Light, Medium or Heavy” designations and the current designations. Here is an example of a “Heavy” motor oil from a Sinclair can of about 1940:

So we now know the answer. Here is a cross reference chart:

Light = SAE 20

Medium = SAE 30

Heavy = SAE 40

So we know definitively that Ford specified SAE 20 when your Model T was new. Back in those days there was no such thing as detergent oil, and multi – viscosity oil was also decades in the future. Let’s consider the advantages and disadvantages of each of these technology advances.

Detergent oil sounds like the oil has some sort of soap in it right? In the 1950’s detergent oil was being introduced to the motoring public and horror stories abounded, particularly among folks who did not know anything about motor oil. There was an old wives tale that if you used detergent motor oil in a old engine that somehow all the oil residue, dirt and sludge that had accumulated would come loose and destroy the engine.

Of course it wasn’t true.

Detergent oil suspends impurities in the oil. These impurities are too small to be captured by oil filters, and consist of such things as soot, combustion chamber by products, and dirt. These things combine to turn the oil dark over time. This is a good thing that you want to happen. When you drain detergent oil all those non – oil compounds drain out with the oil.

Oil viscosity is determined by the rate an oil can be poured through an industry standard orifice at industry specified temperatures. An oil that meets these standards for SAE 30W is branded as such. An oil that meets the standard for SAE 5W is branded as such. The “W” stands for “Winter”. Obviously a lower number flows better in winter test conditions than an oil with a higher number.

Multi Viscosity oils were developed to help reduce engine wear. Most engine wear happens when oil is cold and thick. The oil takes longer to reach wear surfaces when it is too thick to flow properly. This is a particularly serious problem for the Model T because unlike modern cars a Model T does not have an oil pump. So we do not want oil that is too thick to flow.

How does multi viscosity oil work? It sounds like the oil transforms itself when it gets warm doesn’t it? Again, this is a false statement generated by folks who don’t understand oil. Multi viscosity oil essentially stays the same when it gets warm. It does not get thinner like a straight weight oil would. This is a good thing for your Model T.

How about “Zinc” in motor oil? It was greatly reduced in most motor oils around 2007. Does this mean my Model T is going to seize up or suffer some horrible engine damage?

No it doesn’t.

ZDDP was first specified as an automotive additive for the 1955 model year. The reason was that new 1955 cars with ultra high performance engines were using stiffer valve springs to enable higher RPM which yielded higher horsepower. These cars used “flat tappet” lifters along with overhead valves. AS RPM increases, the amount of inertia generated by the camshaft parts requires stronger springs to close the valve and to keep the lifter from hopping up and down on the camshaft. The increased friction from the super strong valve springs in these 1950’s cars caused rapid wear of the camshaft and lifters. This had never been a problem in older engines, and it was never a problem in the Model T Ford.

Bottom line – do you need high ZDDP motor oil for your Model T? No.

With all this being considered, what oil is best for the Model T? Let’s consider one more thing – operating temperature where you live. If you live in a hot, desert environment such as Saudia Arabia where cool morning temperatures are 85 – 90 degrees F and afternoon temperature reaches 120 degrees F you will want to use something like 10W-40.

In areas with average temperature between 40 and 110 degrees F you will want to use 5W-30.

Operating a Model T in winter weather, with temperatures between 0 and 4 degrees F you will want to use 0W-20.

How often should the oil be changed in a Model T Ford? Again we look to the recommendations from back in the day. Here is what Dykes had to say:

So the answer should be to change oil every 1000 miles or every year, which ever comes first.


Use any brand of oil that you like. Like expensive synthetic oil? Fine, just remember that you are draining it in 1000 miles or one year from now, which pretty much eliminates any advantage of synthetic oil.

Use a grade of oil that is suitable for the temperature that you operate the car.

Your Model T holds one US gallon of oil. Over filling will result in lots of blue smoke while the engine is running.

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