When Kelly Tidwell was 13, he bought drain oil for five cents a quart to use in his first car, a '35 Chevy. "We didn't know any better," he tells us. "Oil was oil. We had no information about this."
He has a lot of information about it now. As the co-founder of Pure Power! EHP Lubricants and Lifetime Filters, Kelly has been making oils for more than 20 years. Since most of the rest of us don't know much more about oil than the 13-year-old kid pouring drain oil into his car, we visited Kelly at Pure Power! to learn more.
What's In Your Oil?In addition to the neutral base petroleum, motor oil is packed with ingredients to improve the makeup of the oil and its ability to lubricate under such conditions as friction, load, and heat. Zinc, calcium, boron, phosphorus, magnesium, sulphur, and other chemicals are typically present at different levels. Zinc, which acts as an anti-wear agent, is one of the most significant additives. Additive packs are more likely to be found in greater quantity and be more concentrated in heavy-duty commercial oil (sometimes referred to as "truck oil" or "diesel oil") than in light-duty passenger car motor oil (PCMO). All Pure Power! EHP motor oils are manufactured using commercial-grade additive packs, created to increase the life of the oil and the life of the engine.
Multi-Viscosity OilsViscosity refers to a liquid's resistance to flow, or in the case of motor oil, how well it flows at low and high temperatures. Oil with a high viscosity can't flow as quickly to engine parts at lower temperatures. A lower-viscosity oil is more likely to fail at high temps.
Multi-viscosity oils (sometimes called multi-weight or multi-grade) were created to provide the best characteristics of high and low viscosity. It's a common misconception that multi-viscosity oil changes weight-thickening or thinning-as temperature changes (e.g. that 20W-50 oil will be a 20-weight when it's cold and a 50-weight when it's hot). What really happens is that polymers used to create multi-grade oil chemically react to inhibit thinning at high temperatures. At an operating temperature of 212 to 215 degrees, 20W-50 oil will not thin more than 50-weight oil would at that temperature and will have the characteristics of 50-weight when it's hot, but will never be thicker than the 20W base weight.
The more polymers in the oil, the wider the potential viscosity range-but there is a drawback. Polymer is plastic and can build up inside the engine, preventing the rings from seating in the cylinders, and creating heavy deposits in the heads. For that reason, multi-grade oils with a wide viscosity range (such as 10W-40 and 20W-50) are generally not recommended by Pure Power!
Extra AdditivesOil additives are not recommended except by the people who sell them. The additive packs already in the oil have been carefully created. Intro-ducing additional additives can potentially reduce performance, or cause serious engine damage.
AcidAcid can spoil motor oil by destroying the additive pack. On the pH scale (which expresses acidity or alkalinity of a solution), a total base number (TBN) above 7 is alkaline, 7 is neutral, and below 7 is acidic. Oil needs a TBN above 7 to neutralize acid. Good commercial-grade oils will typically have a base number in the high 9s, and shouldn't be lower than somewhere in the 8s. Pure Power! prints its TBN of 12-14 on every label. Kelly has tested many brands of oil, and found some with TBN as low as 3-close to lemon juice!
Oil ChangesDark, dirty oil doesn't necessarily mean it's time for a change. It means that the additive pack is still working, keeping fuel soot and other particles in suspension in the oil and not settling out in your engine.
"TV commercials telling you to change your oil at 2,000 or 2,500 miles are just trying to sell oil," Kelly says. The correct frequency is not a matter of months or miles, but of whether or not the oil is still doing its job. According to Kelly, a quality oil, at least 10W-30 grade, should be able to go 5,000 miles under normal service; a good commercial-grade 10W-30 or 15W-40 should go 7,500 miles. Change the oil after fewer miles if your car is driven infrequently, unless you're using a good commercial-grade oil with a high TBN.
Reading The BottleThe symbols on a motor oil label can tell you a lot about the oil. Look for two "quality marks" designated by the American Petroleum Institute (API). The round API Service Symbol is divided into three sections. The upper arch identifies the oil's performance level, using the letters S or C followed by another letter. S (for Service) identifies oil intended for gasoline-powered passenger cars and light trucks. SL (approved for all engines currently in use) and SJ (for 2001-and-earlier engines) are the current, and most common, categories. C (for Commercial) identifies oil intended for diesel-powered, heavy-duty trucks (the so-called "truck oils"). Designations are based on additive packs for oils in that category. The most current high level is CI-4. Less current S and C categories are listed on the API Web site at www.api.org. Pure Power! EHP oils are API certified and meet the standards of all of the current C categories as well as the SL category.
The center section of this symbol identifies oil viscosity. The lower arch identifies the Fuel Economy Rating, and refers to a passenger vehicle gasoline engine's ability to meet API energy conservation standards.
The separate "starburst" symbol is an API certification that the oil meets established engine protection and fuel economy standards.
What's The Best Oil For Your Hot Rod?Good commercial-grade heavy-duty oil is a better grade than PCMO, Kelly says, and commercial oils can be used in gasoline engines. For general highway use, he recommends using a good commercial API-certified 10W-30 for longer engine life. Thinner oils with lower base numbers (e.g. 5W-30 and 5W-20) were created to satisfy fuel economy standards, but wear out far more quickly than heavier weights. Ultimately, he recommends checking the label to determine the quality of the additive pack.
FiltersThe most common oil filters contain a disposable, pleated paper/cellulose element. Kelly's criticism of these disposable filters is that the elements aren't porous enough for oil to flow through. They work on the principle that debris will be caught by the paper element as it flows past, but debris can break loose, re-enter the oil, and get back into the engine.
Pure Power! Lifetime oil filters use a stainless steel housing with a permanent, cleanable filter element made from duplex woven stainless steel wire cloth, for absolute filtration of particles 22 microns and smaller. The filter is designed to literally screen out unwanted particles from the oil. In addition to better filtering, Kelly explains, this system actually increases horsepower by eliminating backpressure created by the pump trying to force oil through nonporous material.
There are other issues to consider with paper/cellulose filters. An over-absorbent can "wick out" the zinc and other working ingredients in the additive pack, reducing the quality of the oil.