Is Additive a Fountain of Youth for Engines?

It would be nice if a magic potion could reduce the wear and tear on your car’s engine by half. Instead of the engine falling apart at 100,000 miles, you would still be motoring at 200,000 miles and boasting good gas mileage.

Plenty of products make claims about extending an engine’s life, improving gas consumption and reducing the amount of oil a car burns. But how can you possibly judge the effectiveness of these products? You pour a can of liquid costing anywhere from $5 to $30 into your engine or your gas tank and it becomes an article of faith that it is doing its job.

Several months ago, I promised readers that I would conduct a test on Slick 50, an engine additive that claims to cut engine wear by 50%. Slick 50 is one of many additives that contain polytetrafluoroethylene, better known by the DuPont trademark Teflon, and is by far the best-selling engine additive; it outsells all of its competitors combined.

We all know about Teflon; it is the coating that prevents food from sticking to frying pans. DuPont asserts that the substance is the most slippery known, although the firm is noncommittal about its effectiveness as a motor lubricant.

My test of Slick 50 was not the most scientific possible, but I did set up a test routine that would determine fairly whether it could reduce the engine wear in one of my cars, an older Honda Accord. I wanted to see if Slick 50 could reduce the amount of cylinder wall and bearing wear, as the company claimed.

I took two engine oil samples before using Slick 50 and had them analyzed by Spectometrics, a leading oil analysis firm in Atlanta. (Spectometrics has no connection with Slick 50.) I treated my engine with Slick 50, drove for 3,000 miles and changed the oil. I then drove 3,600 miles, at which point I took a third oil sample.

The analysis showed that the amount of iron had decreased by two-thirds to 13 parts per million, compared to the two samples taken before the treatment. The iron content is generally an indication of how much wear is occurring from the cylinder walls.

In addition, the molybdenum content, a metal used in engine rings, was also reduced by two-thirds to a level of 1.2 parts per million.

“You are experiencing a considerable decrease in wear,” said Carlton Joyce, owner of Spectometrics and a former engineering professor.

He noted that a typical cast-iron engine block has fairly porous metal and is ideally suited to accepting PTFE molecules.

Although Joyce believes PTFE reduces engine wear, he disputes claims that the additives last the life of the engine. His research shows that they begin to lose their effectiveness after about 25,000 miles.

I would also question Slick 50’s claim that it improves engine performance by 8% in tests. I could detect no increase in my gas mileage, although I do believe an 8% change is difficult to detect in real-world driving.

Another bit of advice: Avoid any polytetrafluoroethylene additive that directs you to shake the container before adding it to your engine. That means the polytetrafluoroethylene particles are not properly suspended in the solution and will probably settle to the bottom of your crankcase when you use it.