Motor oil – what to use, when, and why - is a surprisingly contentious topic, especially when it comes to collector cars. I’ve seen so-called gentlemen get into fistfights over the stuff at more than one holiday party, when the effects of Mobil Synthetic Blend and Smirnoff vodka prove more than one could handle.
As New Years approaches I thought I’d share our philosophy at Robison Service, particularly as regards collector cars.
- We should begin by looking at what we want the oil to do, in a vintage vehicle
- We want an oil that has high natural strength – otherwise referred to as film strength or barrier strength. This is the oil’s ability to prevent metal on metal wear in the moments before the oil pump begins delivering pressurized oil to the bearings.
- We want an oil that’s fairly thick at running temperature, because older engines have sloppier clearances, but not so thick as to be a drag on performance
- We want an oil with zinc additive for the metallurgy of vintage motors
- We want an oil with strong detergents to clean what are often dirty old motors
- We want an oil that’s free of waxes and compounds that form sludge in long storage and short cycle use.
There are not many oils marketed for this purpose. The one we are using more and more is Castrol Syntec Edge 5-50 Classic Car Formula. It’s replaced the older Castol GTX for vintage cars. Mobil – to the best of my knowledge – does not have a comparable oil.
Readers of my columns know I’m a big believer in synthetic oils. Their superior strength and durability are beyond dispute. Some vintage car owners argue that durability does not matter in a car that’s driven 1,000 miles a year with annual oil changes, but the other features of synthetics DO matter.
Synthetic oil is thinner when cold and stays thicker when hot. That means a synthetic 5-50 is more pumpable than a conventional 20-50 on cold start, yet is actually thicker at 200 degrees when the motor is running.
The fact that synthetics are thinner when cold means the oil pump will begin circulating oil faster. Engineers suggest that most wear happens in the seconds before the oil system gets up to pressure so that’s a vital benefit.
Older engines need a different set of additives than those optimized for new cars. Syntec Classic is one of the few oils to offer vintage-tailored additives.
There are so many different grades of oil now, for so many purposes, that it’s difficult to make a choice for these older vehicles that predate the modern specifications. We do our best, but we recognize there may be more than one answer. The main thing we want to avoid is wrong choices that can damage engines.
What oil are you using in your collector car, and why?