Robert Todd Carroll
slick 50 and other engine oil additives
You may have heard the commercial or seen the ad:
Multiple tests by independent laboratories have shown that when properly applied to an automotive engine, Slick 50 Engine Formula reduces wear on engine parts. Test results have shown that Slick 50 treated engines sustained 50 percent less wear than test engines run with premium motor oil alone.
There are about 50 other products on the market which make similar claims, many of them being just duplicate products under different names from the same company. The price for a pint or quart of these engine oil additives runs from a few dollars to more than $20. Do these products do any good? Not much. Do they do any harm. Sometimes.
What's in these miracle lubricants, anyway? And, if they're so wonderful, why don't car manufacturers recommend their usage? And why don't oil companies get into the additive business? And where are these studies mentioned by Petrolon (Slick 50)? Probably in the same file cabinet as the tobacco company studies proving the health benefits of smoking.
The basic ingredient is the same in most of these additives: 50 weight engine oil with standard additives. The magic ingredient in Slick 50, Liquid Ring, Lubrilon, Microlon, Matrix, QM1 and T-Plus from K-Mart is Polytetrafloeraethylene. Don't try to pronounce it: call it PTFE. But don't call it Teflon, which is what it is, because that is a registered trademark. Dupont, who invented Teflon, claims that "Teflon is not useful as an ingredient in oil additives or oils used for internal combustion engines." But what do they know? They haven't seen the secret studies done by Petrolon (Slick 50).
PTFE is a solid which is added to engine oil and allegedly coats the moving parts of the engine.
However, such solids seem even more inclined to coat non-moving parts, like oil passages and filters. After all, if it can build up under the pressures and friction exerted on a cylinder wall, then it stands to reason it should build up even better in places with low pressures and virtually no friction.
[Rau]
This conclusion seems to be borne out by tests on oil additives containing PTFE conducted by the NASA Lewis Research Center, which said in their report, "In the types of bearing surface contact we have looked at, we have seen no benefit. In some cases we have seen detrimental effect. The solids in the oil tend to accumulate at inlets and act as a dam, which simply blocks the oil from entering. Instead of helping, it is actually depriving parts of lubricant."
In defense of Slick 50, tests done on a Chevy 6 cylinder engine by the University of Utah Engineering Experiment Station found that after treatment with the PTFE additive the test engine's friction was reduced by 13.1 percent, the output horsepower increased from 5.3 percent to 8.1 percent, and fuel economy improved as well. Unfortunately, the same tests concluded that "There was a pressure drop across the oil filter resulting from possible clogging of small passageways." Oil analysis showed that iron contamination doubled after the treatment, indicating that engine wear increased. [Rau]
Another type of additive is zinc dialkyldithiophosphate. Zinc-d is found in Mechanics Brand Engine Tune Up, K Mart Super Oil Treatment, and STP Engine Treatment With XEP2, among others. The touting of zinc-d as a special ingredient in engine oil additives is a little like the Shell ads which touted "Platformate." (Most gasolines have similar additives but under different names.) Zinc-d is an additive in most, if not all, major oil brands. The wonder oils just put more of the stuff in a 50 weight engine oil. It would be useful if your engine were ever operated under extremely abnormal conditions where metal contacts metal: "the zinc compounds react with the metal to prevent scuffing, particularly between cylinder bores and piston rings....unless you plan on spending a couple of hours dragging your knee at Laguna Seca, adding extra zinc compounds to your oil is usually a waste.... Also, keep in mind that high zinc content can lead to deposit formation on your valves, and spark plug fouling." [Rau]
If zinc-d is so good for your engine, why haven't oil manufacturers been putting more of it in their standard mix of oil and additives? Actually, oil companies have been decreasing the amount of zinc-d because of research evidence which indicates that it seems to adversely affect catalytic converters, causing them to deteriorate.
The bottom line is that outside of the testimonials of happy and satisfied customers and the guarantees of company executives about the wonderful effects that studies have shown will follow the use of their products, there isn't much support for using oil additives. Of course, there are those millions of customers who buy the stuff: aren't they proof that these things really work? Not really. They're proof that this stuff really sells!
Though some additives may not contain anything harmful to your engine, and even some things that could be beneficial, most experts still recommend that you avoid their use. The reason for this is that your oil, as purchased from one of the major oil companies, already contains a very extensive additive package.
[Rau]
This package is made up of numerous, specific additive components, blended to achieve a specific formula that will meet the requirements of your engine. Usually, at least several of these additives will be synergistic. That is, they react mutually, in groups of two or more, to create an effect that none of them could attain individually. Changing or adding to this formula can upset the balance and negate the protective effect the formula was meant to achieve, even if you are only adding more of something that was already included in the initial package.
On the other side of the engine block are those additives which will cleanse your engine, not coat it. Stuff like Bardahl, Rislone and Marvel Mystery Oil claim they can make your engine run quieter and smoother; they can reduce oil burning. These are products which contain solvents or detergents such as kerosene, naphthalene, xylene, acetone or isopropanol. If used properly, I suppose these products will strip off your Teflon and zinc protective coatings! But unless you have a really old and abused car, you probably have no need of stripping away sludge and deposits from your engine. Thus, you probably have no need for these wonder cleaners. And, if you overuse such products you can damage your engine by promoting metal to metal contact.
Also, if you use a synthetic oil, such as Mobil 1, you are advised not to use any engine treatments or additives. Mobil claims that
Tests have shown that some additive supplements may significantly alter the performance and properties of any lubricant. In several cases, additive supplements have been detrimental to viscosity, storage stability and reduced protection against the formation of deposits.
Finally, you may have seen the commercial where two engines are allowed to run without any oil in them and the one which had the special oil additive keeps on ticking after the other engine has conked out. This may be appealing to the car owner who never changes his or her oil or who runs his or her car without oil, but it should be of little interest to the person who knows how to take care of their automobile.
The skeptic's advice? After consulting with philosopher/botanist/ex-auto garage owner Rich Ownby, my advise is to change your oil and oil filter regularly and if your car is getting old and cranky use a single viscosity oil (30 weight is good), not a multi-viscosity such as 10-40. That multi-viscosity stuff is for the younger set, according to my advisor. And don't forget to change the fuel and air filters at the recommended intervals.
further reading
- "Snake Oil! Is That Additive Really A Negative?" Fred Rau, Road Rider,August 1992.
- QUAKER STATE ADS FOR SLICK 50 ARE FALSE AND MISLEADING, FTC CHARGES July 16, 1996 FTC press release
- Car Talk with Tom and Ray
Robert Todd Carroll
philosophical skepticism