Piston Slap: And what of Mustangs using premium grade mineral oil?

Don writes:

Good day! I no longer have my older Mustang, but upon changing the oil on my 2019 Mustang GT (which came with synthetic blend oil) my local dealership in Ontario, Canada, used what they called a “premium grade mineral oil.” But the owner’s manual specifies to maintain the use of synthetic blend oil.

The dealer’s service department defended the mineral, even after I expressed concern that the cylinder walls of the new 5.0-liter block (since 2018) do not have liners; instead they have a process called “arc weld,” I think!  What is the impact of this oil on my engine?

Sajeev answers:

Bizarre name aside, there isn’t a negative impact to your engine, especially if you switch to a full synthetic sooner rather than later (and continue with full synthetic going forward.) But dumping the oil you currently have is far from mandatory, as dealerships aren’t in the business of destroying engines with the wrong oils. Even if this Ford dealer ignores its corporate overlords and uses something besides Motorcraft oil, it likely partnered with a major oil company for beaucoup kickbacks better pricing on quality oils for its wonderful customers.

Long story short, odds are the “premium grade mineral oil” you bought is something close to the Motorcraft Canada’s “Super Premium Motor Oil.” This is because all oils for sale in North America are formulated to meet a minimum of performance standards—and that minimum won’t hurt your engine in a single oil change.

As an aside, Ford also makes this complicated because the same oil has different packaging between the U.S. and Canada. The stateside stuff comes in red bottles with the logical name of “Motorcraft Synthetic Blend” on the label. Canada uses a black bottle and calls it the aforementioned “Super Premium.”  It’s the same blended synthetic oil in different bottles, and it is suitable for almost every Ford’s needs (it’s not suitable for a Shelby GT350 on a race track).

If you still have concerns, change your oil elsewhere and buy the type/brand of your choice from the parts store to ensure you get exactly what you want. If this car will be a keeper for many decades, switch to a full synthetic oil and Motorcraft oil filters. The latter is a consistently good quality filter at a cheap price. (Well, at least that’s true in the U.S.)

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