Motor Oil Additives - Expert's Opinions

Bob Bidonde

Bob Bidonde

Well-known member
A recognized motor oil expert gave a talk about oil at our last club meeting.
ZDDP: It was concluded that the ZDDP is not necessary in the Model A's engine because it is a low speed hi-torque design with a max RPM of 3000. The use of ZDDP came about because of the emergence of high reeving overhead valve engines. Overhead valve engines had difficulty getting sufficient motor up into the cylinder heads, so ZDDP provided extra lubricity for the valve trains. Using ZDDP with a non-detergent motor oil can be harmful because the ZDDP will buildup and clog oil passages. Detergents in a motor oil prevent the excessive buildup of ZDDP.
Multi-Viscosity Motor Oil: The use of modern SAE 10W40 detergent motor oil is recommended for the Model A because it has superior cold & hot temperatures performance, and it does not cause the buildup of sludge in the oil pan. Down to zero degrees F, the 10W30 has a viscosity with good flow characteristics to assure good lubrication. The Model A's engine runs in a temperature range of 160F to 190F. The 10W40 oil reaches a viscosity of 40 at 212F, so at operating temperature range of the Model A's engine, the 10W40 has a viscosity in the mid range of 20 to 30.
Marvel Mystery Oil: The expert's opinion is that there is no harm in using Marvel Mystery Oil in the motor oil according to the manufacturer's instructions.
STP: STP is intended to increase the viscosity of oil, and it is not necessary in multi-viscosity motor oil. However, it has value in the transmission because it raises the viscosity of 75W145 gear oil enough to aid in shifting without grinding. In other words, it raises the oil's viscosity enough to increase the deceleration of the gears.
 
All oil, including multi viscosity oil, will decrease viscosity with higher temperature. It is just that multi viscosity oil has a shallower slope so that at low temperature it is still runny enough to not harm the engine at at high temperatures it is not too thin so that it will not harm the engine.
 
I can write a little bit something reliable about this. Tribology was my profession.


ZDDP is an additive that only works when local temperature spikes rise sharply and metal-to-metal contact occurs. In other words, it acts as an anti-seize agent when the lubricating film briefly fails. It's not a direct lubrication improver. Unlike MoS2, it leaves virtually no additional residue in the combustion chamber.


Multigrade oil is correct. SAE 10W-(...) is only useful if the engine is also driven in winter. A 20W-(...) is better because it has a higher base viscosity. This results in less oil consumption/sweating in an older engine. SAE 20W-40/50 is a good choice.


Dispersed oil (HD) is a perennial point of discussion. But it keeps a rebuilt engine clean.


MMO is a perfect top oil in the fuel. I've used many cans of this at a 1:250 dilution in all my classic cars with sight'n results. It cleans the fuel-system and reduces deposits. (Unfortunately, it's no longer available/permitted in the EU.) I wouldn't use it in the oil pan. There are some uncertainties involved.


STP is a synthetic viscosity thickener that temporarily helps old, worn-out engines. It's very bad for cold starts. Its effectiveness is quite limited because the extremely long molecular chains are literally cut up by mechanical action, and the viscosity thins out.

 
Teacher: Children what do you want to be when you grow up?
Johnnie: A fireman. Bobby: A policeman. Laurie: A nurse.

Werner: A Tribologist.

Teacher: Werner, stop making up funny words!
 
old ugly said:
just a question as i don't know why.

Why is synthetic not part of this topic?
Click to expand...

Because synthetic oil is not an additive.

You can use it, if you want. If the viscosity numbers are "correct" for your application, the synthetic oil will work quite well. It is more stable at higher temperatures and flows well when cold.

On a Model A without an oil filter, we tend to change the oil quite often. Henry said 500 miles using oil of his time. Some people go a bit longer with modern oil. And even longer with an oil filter installed. There is no PCV system to pull out water and fuel vapor, and we know the Zenith carburetor is sometimes too rich (putting unburned fuel in the oil). You change the oil to get that stuff out.

I change my oil fairly often (~500 miles) so in the past I stayed away from synthetic in the Model A because it was more expensive and I felt that was a waste to be draining so often. (I use it in another old car I have.)

But now the price difference is shrinking. I just looked and 4 quarts of my conventional oil is $16 and 4 quarts of the same oil as synthetic is $23. I might start using the synthetic in the A, once I use up the bottles of conventional oil I have on hand. YMMV.

.
 
Why is synthetic not part of this topic?[/QUOTE]

If you have an engine that leaks even a tiny bit when using non-synthetic oil, it will leak a lot more with synthetic oil. One measure of goodness in oil is its ability to wick into tiny spaces, as in penetrating oil. Synthetic does this better than conventional.

I tried it in my A out of curiosity and it only took a one-mile drive to see that I needed to immediately change back to conventional.
 
Werner said:
I can write a little bit something reliable about this. Tribology was my profession.

STP is a synthetic viscosity thickener that temporarily helps old, worn-out engines. It's very bad for cold starts. Its effectiveness is quite limited because the extremely long molecular chains are literally cut up by mechanical action, and the viscosity thins out.
Click to expand...


i wonder if there is synthetic additives?
it is just a question i don't know.
 
the oil has additives that the refinery uses and adding different ones can make the oil less that it originally was if the additives clash
 
Higher levels of ZDDP were in all motor oils used for all makes and models in days past. It provided good wear protection for all engines. When catalytic converters were introduced, high levels of ZDDP were found to destroy them. Thus, all common oils now have a reduced level (half or less). With all the discussions of oils for A's. no one has yet explained to me what is in
today's oils that compensates for the wear protection provided by ZDDP, particularly in valve trains.
 
ZDDP is a high/extreme pressure lubricant. It was used to prevent wear between the cam and flat lifters as spring pressure was increased to stop valve float at higher RPMs. ZDDP kills catalytic convertors so they started using the roller lifters in production cars. Ethyl also kills cats but it kept the valves lubricated. They added hard seats to fix that wear problem - which also isn't a problem in the A due to low valve spring pressure.
 
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