Oil additives and the damage they do.
There are countless over the counter oil additives on the market, as there have been for a number of years. In recent years a number of companies have appeared on the scene with huge national television advertising campaigns, racecar sponsorship, and more, all designed to make the consumer believe that the products really work and you are doing yourself a favor by adding these to your car. The fact is that these products are not necessary, do very little to help your engine, and in many cases may actually do more harm than good. The major car companies do not endorse any of these products and in fact your owner's manual will undoubtedly advise you to avoid them.
Consumers Reports did a test (10/98) in an attempt to verify, or rebuke, one company's ad which claimed that their product "bonded" to the engines moving parts forming a protective barrier against wear. The ad claimed that their test car ran all over Southern California, in stop and go traffic, with the air on, for 4 hours and 40 minutes with no oil. The ad also claimed that the only reason the driver stopped was to get something to eat. Pretty unbelievable. In an attempt to prove or disprove the viability of the ad, Consumer Reports tested two Chevrolet Caprices, both with identical zero time rebuilt V6 engines. Both cars were broken in with normal petroleum oil per the manufacturer's recommendations. The oil and filter were then changed with one of the cars receiving the prescribed dose of this magic additive. Both cars were then driven for about 100 miles, allegedly long enough for this magical bonding to occur, and the oil subsequently drained. Both were then driven again, now with empty crankcases, in normal traffic to see how long they would last. Interestingly both engines failed, almost simultaneously, after about 14 minutes of driving thus proving the claims of the additive manufacturer to be nonsense. Consumer Reports notified the FTC of the test and their results and the manufacturer was subsequently forced to stop running the ad.
There are some over the counter additives that contain Teflon or PTFE. Once again the ads claim that the Teflon bonds to the internal working parts of the engine forming a slippery surface (like your Teflon frying pan) and therefore reducing wear. Fundamental laws of Physics prove that such claims are impossible, as the temperatures in internal combustion engines (200º-250ºF) are insufficient for any bonding to occur. Further, independent oil analysis labs have observed that the suspended Teflon particles actually tend to accumulate the microscopic metals that are normal in engine oil formulating much larger, and potentially much more harmful, deposits in engines than would normally occur if straight motor oil had been used. In some cases, the oil filters became clogged, oil pressures dropped across the filter and oil analysis showed significantly more wear than oil alone. Similar to the previous situation, the FTC challenged the makers of products with PTFE on their claims of "coating of PTFE" and "reduced engine wear" based again on Consumer Reports findings of "no discernible benefits" from use of the product. The makers of these products agreed with the FTC in a settlement to stop using the above phrases in their ads.