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Oil Change Frequency Advance

If you're the DIY type who changes your own oil, you probably return the used oil back to the retailer for recycling. But that brings up a good question: if it can be recycled and used again, why even change it at all? It's not that the oil goes bad, but the oil in your engine becomes contaminated and loses efficiency. You want clean oil lubricating your engine, not contaminants and grit.

The slight clearance between moving parts—say, between piston rings and cylinder walls—allows trace amounts of burned fuel to mix with the oil, contaminating it. Over time, these contaminants will turn your oil dark. The oil filter keeps a lot of that junk from circulating in your engine, but it has a limited capacity. When the filter can no longer keep the contaminants out of your motor oil, it's time for an oil change. If you go too long without one, the contaminants build up and cause costly sludge issues and reduce the oil's viscosity.

What is Oil Viscosity?

Viscosity is a science term that sounds like it would mean oil's thickness. That's not quite right though. Viscosity is actually the “measure of its resistance to deformation at a given rate" in geek speak, or simply a fluid's resistance to flowing. High viscosity fluids like molasses are resistant to flowing compared to low viscosity fluids, such as water, that flow freely. So the viscosity measurement on the front of the oil bottle is its resistance to flow at a given temperature. Let's look at how to read the numbers.

The Society of Automobile Engineers developed a scale to grade engine oils for protection during cold starts in the winter and at operating temperature in the summer. You've seen this on oil containers in the XW-XX format. The first number is the winter (W) rating for cold starts in 0 degrees Fahrenheit, while the second number is the rating for an operating temperature of 100 degrees Celsius. Some common oil viscosities are 0W-30, 5W-30, and 10W-30, meaning they all provide the same protection at operating temperature, but the 0W being the easiest flowing in winter temps. This is a good thing in Alaska, as you don't want to try and start your F-150 with the aforementioned molasses in the crankcase.

Can I use a different oil viscosity?

Like many engine related questions, the answer is maybe. Swapping for a higher viscosity oil can provide more protection when hot, but it will also cost you some power and gas mileage. On the other hand, switching to a lower viscosity oil *could* gain you some additional horsepower, if you remember playing Gran Turismo, along with increased gas mileage. The potential downside is less engine protection between critical parts. Is that really worth 2 horsepower or a 0.5 MPG gain to lessen engine protection? Probably not. Note that the manufacturer's engineers used a specific weight of oil when building, testing, and certifying your engine. If you want all the horsepower, gas mileage and low emissions that the factory says the engine makes, then you want to stick with the oil it was designed for. If your oil cap doesn't list it, consult your owner's manual.