Each car you own is a huge investment, one of the biggest you’ll ever make. It stands to reason that you’ll want to take proper care of it, to make sure it lasts as long as possible. Yet, most of us don’t know all that much about proper automobile maintenance. (I’m grateful for a wonderful son-in-law who is an expert in these things.) There are plenty of companies who are eager to take advantage of our ignorance.
Ads for oil additives target our concerns about engine longevity. By claiming to reduce friction, add a protective coating to the metal, and/or prevent the build-up of engine deposits, and they supposedly protect damage incurred by “cold starting” your car, as well as increase gas mileage and horsepower. Wow, that sounds great!
So, should you be buying those cans of Slick 50, STP, and Tufoil? Do they actually do what they claim to do, or are they a waste of money? Worse, can they damage your engine?
I found a very helpful article that answers these questions. While I certainly can’t recommend everything* on this website, in this case, I think the author is spot on.
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* Sadly, author Robert T. Carroll denies the existence of God and clearly holds His followers in disdain.
Compost 
Nice articles. As a professional mechanic I have never recommended any kind of oil additive, with the exception of those made by the BG corporation. Even BG products I haven’t done any research on so their oil additive may be just as useless as all the others, despite being used by many dealerships. Really, the author of the skeptic’s article hit the nail on the head when he said that staying on top of oil changes is key to engine longevity. I’ve replaced dozens of engines because of neglectful owners who chose to not keep up with this most basic bit of maintenance, and I’ve also seen many engines last hundreds of thousands of miles because they were maintained. Moral of the story: Change your oil. In fact, keep up with all your maintenance needs and your car will last much longer than it would otherwise. Pass on the silly additives,take good care of your car, and it will hopefully take good care of you.