Hagerty’s Larry Webster sat down with Shawn Nguyen and Michael Thomas, both engine oil experts from Shell/Pennzoil, as part of the Hagerty Drivers’ Club exclusive live stream. They spoke about the often-confusing subject of selecting the right oil for your classic car.
Larry shared an anecdote about picking the right oil for his air-cooled 1969 Porsche 911, and the owner’s manual only mentioned the operating temp ranges and listed single-weight oils. He ended up selecting 15W-40 Rotella T4 and it turns out that was a great choice for his flat-six, but also for lots of classic car engines.
Oil formulas for late-model cars are always changing, and as roller cams and roller followers became the norm, there was less need for ZDDP, better known as zinc, which could cause harm to catalytic converters. Automakers were also looking to get thinner, low-viscosity oils that present less drag and parasitic loss on the engine to eke out better fuel economy. That means the most popular oils on the shelf are less and less suited for your classic.
For classic car applications, the guys at Shell often recommend Rotella, and although it’s thought of as a diesel engine oil, its high-zinc formulation that’s made to fight scuffing on metal-to-metal contact is just what older engines need. So make sure the oil you select for your classic engine is from a quality brand and that it has plenty of ZDDP. You don’t have to guess though, you can get a recommendation from Shell by calling 1-800-BEST-OIL.
Motorcycles are different
For motorcycle applications with a wet clutch that shares crankcase oil with the engine, an oil that’s too slippery will prevent the clutch from fully locking up. Make sure to check for an MA and MA2 ratings. Both are made for motorcycles, but the MA2 ratings are for later model motorcycles built since 2008.
Synthetic oils work better under pressure
Synthetic oils are purer, have more stable viscosity, and a higher tolerance to heat.
As a rule of thumb, every 20-degree increase in temperature over the oil’s operating range cuts its useful life in half. For synthetic, that temperature is higher, so for demanding applications, like racing, it is worth the added cost of synthetic. Otherwise, your classic should do just fine with conventional.
Drive your car
Burning gasoline creates water vapor, which can accumulate in the crankcase. Shor drives don’t allow oil to get up to temp long enough to remove the water. Bringing engine oil up to temperature for 20 minutes or so at a time will give enough time for water to evaporate out of the oil.
Change it at least every year
Other compounds that wind up in your oil due to gasoline combustion, like acids, aren’t filtered out. Additives also separate and degrade, even when the oils aren’t opened. Change your oil every year, and don’t use an oil that’s more than four years old.
Good luck with your lubricating! For more details on what type if oil is right for your car, download Shell’s informational brochure here.