Diesel Motor Oil

Bob Bidonde

Bob Bidonde

Well-known member
I have a few gallons of Mobil 1 diesel oil, and I am thinking about using it in my Model A's. Are there any negative consequences to using diesel oil in a model A or Model B engine?
 
As long as the viscosity is correct it should be fine but if your engine has a lot of sludge it could loosen that up. We used diesel engine oil in our gas engines on the farm all the time with no problems.
 
This oil was originally marketed to fleets by the oil companies as a good universal motor oil that they could deploy in both their diesel engines and their gasoline engines. The fleet guys liked not having to stock multiple different engine oils. Everything used the same oil.

Then the US EPA got involved... They said that it could not be marketed as a gasoline engine oil because the higher ZDDP in it fouled the catalytic converters on the gasoline vehicles. The EPA pushed for lower ZDDP levels in all gasoline engine oils, and made them stop marketing this "diesel oil" as suitable for gas engines.

So, without changing the formulation of the oils, they stopped marketing them as diesel and gas engine oils, and started calling them just diesel oils.

We don't have cat converters on our Model A's, so the EPA does not care if we use the diesel oil in our cars. The higher ZDDP does no harm.

Back when the Model A was new, Ford said to use SAE 40 weight oil in the summer, and SAE 20 weight in the winter. I think the 15W40 diesel oil is a good modern equivalent to what Ford originally had in mind.

YMMV.
 
Oil has always been a controversial subject like religion and politics. Most articles indicate not to use diesel oil and reference catalytic converters which of course we don't have. But there are ingredients that may not be good for gas engine use. Schwalm's specified Rotunda diesel for their rebuilt engine in my coupe. I broke it in and ran with it for awhile. It bothered me so I changed to "automobile" oil. For a low-tech not-often used vehicle, it may not make much difference. Here's a link to one of many articles: https://urbsgarage.com/can-you-use-...ty,performance and increased fuel consumption.
 
Hey Bob.


That's my past job area of ​​expertise at work.


Oil specifically only manufactured for diesel engines comes from Shell. Generally most oils are suitable for both gasoline and diesel are also available.
Check the API specification on canister: It will mention C(.) and S(.) followed by one letter.

S is the specification for gasoline engines. The higher the letter in the alphabet, the better suited the oil is to modern engines. I wouldn't go higher than SH or SJ for this Ford.
Modern oils are designed for engines with extremely low oil consumption. In engines with higher oil consumption, this results in excessive combustion residue in the combustion chamber and on the piston crowns.
The SAE classification should also be considered. 20W-40 or -50 is suitable for the A.


Mobil 1 is a very modern, very good oil here in Germany. For modern engines.
 
Speaking of Mobil-1, I noticed an add in Hagerty Magazine for the first time Mobil-1 Classic Car Formula. I thought that was interesting.

My wife's (C-4) Corvette was engineered to run Mobil-1 only. I won't even let the dealership change the oil in the thing. It gets Mobil-1, and a AC Delco filter only.
 
Engine oils are designed for specific applications based upon rigorous testing by the manufacturer. Additive packages and base oil qualities are designed to meet the requirements set by the vehicle manufacturer that will meet warranty requirements. Diesel oils are designed for expected operating conditions and gas engine oils for their specific use. If your driving to the ice cream shop, most engines would likely be fine with either. If your touring and logging long distant miles I would seek input from a respected engine rebuilder. Either case, keep the oil changed at suggested intervals. Modern additives are great at suspending sludge/solids in the oil.
 
Bob Bidonde said:
I have a few gallons of Mobil 1 diesel oil, and I am thinking about using it in my Model A's. Are there any negative consequences to using diesel oil in a model A or Model B engine?
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Bob: If you want to be sure that the Mobil 1 diesel oil will work OK in your Ford Model A engine, it is best to convert your Model A engine to run off of diesel fuel.....like this one:

578019


578020


Maybe more work than you wanted, but that way you will have no worries about the diesel oil compatibility! :D

Brad in Maryland



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>>"Modern oils are designed for engines with extremely low oil consumption. In engines with higher oil consumption, this results in excessive combustion residue in the combustion chamber and on the piston crowns"
>>"Additive packages and base oil qualities are designed to meet the requirements set by the vehicle manufacturer that will meet warranty requirements."

Most modern engines including Subaru and Audi that I know of, use low tension piston rings and end up using oil like crazy. Here, there are consumer laws that state what you buy should last to "expected durability" regardless of warranty. Only Mitsubishi is known to replace engines with known problems, well past warranty.
 
Oil formulated for Diesel engines is fine in ours but NOT NOT put Diesel fuel in a petrol (gas) powered engine. The compression ratio is too low for it to burn cleanly and it leaves behind a gritty carbon deposit that will grind the insides of your engine very quickly.
I recall my father in law telling me this years ago and only about 3 years ago, I was filling the Model A with fuel I had stored and I forgot that there was a 4 litre can of Diesel fuel in there somewhere. It ended up in the tank and by the time I had burned half of the tank of fuel, the engine was blowing blue smoke. I was amazed at how quickly the damage was done. The engine had an unscheduled rebore.
 
The opinions regarding using diesel motor oil in Model "A" & Model "B" engines are overwhelming in favor of doing so. I thought that this would be the case. Thanks all for your responses.

 
I have been using 15W40 diesel oil in my '35 Packard Super Eight engine for several years as recommended by many Packard folks. For my '31 Model A roadster, I have been using 10W30 for many years. Based on the above input, I'm leaning toward using the diesel in the Roadster also. Sure would be easier using the same oil in both cars.

Glen
 
I currently use Shell Rotella T4 15W40 in my coupe. It's a conventional (non-synthetic) oil and it's the cheapest oil my Walmart sells. 1200 miles, two oil changes, and no issues or oil consumption.

I'm impartial when it comes to the oil wars, so long as you put 10w30 or 15w40.
 
Mike1291 said:
I currently use Shell Rotella T4 15W40 in my coupe. It's a conventional (non-synthetic) oil and it's the cheapest oil my Walmart sells. 1200 miles, two oil changes, and no issues or oil consumption.

I'm impartial when it comes to the oil wars, so long as you put 10w30 or 15w40.
Click to expand...


X2. My choice as well.:)
 
Synchro909 said:
I use the sae oil in all of my cars - modern ones included. Fuchs Titan Universal 15W40
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Synchro, please allow me to describe this in a little bit more detail.


You wrote "SAE". SAE has nothing to do with the type of oil, it is only an indication of the viscosity.

The type of oil is indicated by the "API", it's listed on the canister too. These are the properties regarding oil composition, combustion residues. For gasoline oils, they begin with the letter “S”. (Diesel Engines "C".) Followed by 1 more letter that describes the Quality class.

Your canister should have “SL” written on it. This is a simple mineral oil for simple engines.


Btw., I like that you use German Fuchs oil! I worked there as consulting freelancer for many decades.
 
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