‘Is this oil thick enough for my car?’

DEAR TOM AND RAY:

I just bought a new Mazda, and the owner’s manual states that I should use 0W-20 oil. I wonder if that is too lightweight for summer travel at interstate speeds, and would it not cause the engine to wear more than using 5W-30? The vehicle is a CX-7 with a 2.5- liter I-4 non-turbo engine. I like getting 100,000-plus miles on my vehicles: I currently have an ’03 Protege with 120,000 miles and a ’97 Toyota with 140,000, and I would want this CX-7 to get that kind of use

— Jim

RAY: It’s good stuff. My brother uses it in salads.

TOM: Car manufacturers have been pressuring oil companies to make oil better and less viscous. And they’ve done it.

RAY: Just because oils are less viscous (thick), that doesn’t mean they don’t lubricate, dissipate heat or protect well against wear and tear. It just means they do all that stuff while creating less friction, which means you get better mileage and longer engine life.

TOM: You’re probably not old enough to remember when cars routinely took 40-weight oil in the summer and 20-weight oil in the winter. That stuff was real sludge. You could still see the dinosaur bones in it.

RAY: Then, multiviscosity oils were invented. So, for instance, you could use a 10W-40 oil that would act like a 10-weight (thinner) oil when the temperature was low and a 40-weight (thicker) oil when the temperature was high.

TOM: And, through the years, as lubricant technology has improved, the viscosity of the oils has dropped, to the point where we can now use a zero-viscosity oil in cold weather.

RAY: It also means the oil coats the inside of the engine more quickly — in a fraction of a second after startup — which protects the engine from wear and tear during cold starts, and makes it last longer. It also means the engine starts more easily in cold weather. Pretty good stuff, huh?