Re: Can synthetic fluids be used in Packards?

Posted by JeromeSolberg On 2021/5/5 17:36:00

I will write here what I understand about synthetics. Oils are a thing many people have many different opinions about.

The main benefits of synthetics is they have a tighter control of the distribution of hydrocarbon chain length. All engine oils have a range of hydrocarbon chain lengths, longer molecules provide better lubrication at high temperatures but can lead to sludge. Shorter molecules are better at low temperatures, but can evaporate at high temperatures. As engine oils wear, some chains break, and some chains re-combine to make longer chains. If a chain gets too long, it essentially creates sludge. If a chain gets too short, it creates a light molecule that evaporates at high temperatures.

Synthetic oils, because they have a better control of hydrocarbon chain lengths, tend to last longer before an oil change is necessary, as it takes longer before a significant proportion of the chain lengths go out-of-range for proper lubrication. In certain applications because of their tighter control of viscosity they are better for wear as well, but generally in engines which have very tight tolerances.

In older engines which were not designed with synthetics in mind, the performance advantages of synthetics are mainly that they allow you to postpone engine oil changes, hence the engine manufacturers which say you can change the oil every 25,000 miles, etc. In an older car which is not driven very much, you probably will want to change the oil more often than the accumulated heat cycles would otherwise warrant it, which probably makes the use of synthetics kind of going overboard. But having a Packard is going overboard anyhow.