Passing the common sense test again.

Cars and Trucks:
That fix a flat you buy in a can? I once seen a woman with a shredded tire try to fill one. I helped her out by changing the tire. She was sweet.

Additives: Additives are an anathema. I hate most additives with a passion. Here's why. They prey on the unsuspecting. They promise results, guarantees that are impossible to deliver. This is a multibillion market to steal from you. I once taught classes on how to identify and recognize outrageous additives. I purchased quite a few additives and displayed them in class.
The first was a Plastic bottle of oil. In a nutshell I would always read the back label. Warning do not use this product in vehicles built after 1930. Equipment damage can result or something like that. There is a label on the back of the bottle. A round doughnut. You will see two symbols The API and the SAE within that doughnut. That is the seal of approval from the American Petroleum institute and the Society of Automotive Engineers.
The next time you roll into Wallmart. Stay away from the extra cheap stuff and look at the back. the later grades of oil are L, M, N.
Now that you know you can pass the common sense test on this one.

Engine additives
1. I have seen many. They seem to question public intelligence. They prey on the weak and the ones who need a quick fix. There are few quick fixes in a can.
Examples of what I have seen.
Teflon additives. They are virtually worthless and have been known to clog oil filters. Dupont was sued by vendors who were supplied by Dupont for teflon. The companies won and Dupont lost. Why? Because it is a multi-billion dollar business.

2. What I call (Stop Knockers) These are additives that can actually stop the knocking you hear in your engine. However they are thicker than dog snot on a hot day. Honey like, you pour the product in and the knocking is somewhat softened. What does it do? On the microscopic level the hydraulic molecules become thicker. Your bearings get coated. Cam bearings, Crankshaft bearings. Wrist pins and whatever else.
The problems? You are mucking with the additives already instituted by the API and the SAE. You are rendering them ineffective. Your compression chamber gets a very light coat of oil each and every time your piston goes up. When the piston comes down and the explosion happens I want you to remember this. the only thing protecting that cylinder wall from enormous heat over millions of times are the API and the SAE people. You want to shorten the life of your engine?
3. Zinc Additives. They design these products to catch your attention from the packaging. Why are people throwing excessive amounts of zinc in the engine? Look at the back of the bottle will you? See an SAE or API stamp of approval anywhere?
4. Coolant Cloggers and radiator fixits. If you change your coolant frequent enough you will never be tempted to buy anything that will clog water passages. I don't give a damn what the bottle says. If it stops a radiator leak it hampers an engine from cooling. Water pumps and vital water jackets. Engine coolant by another name is antifreeze. There are properties that prevent the corrosion and add lubricity to the water pump. The antifreeze also raises the boiling point.
5. Transmission fixits. An automatic transmission is one of the most complex and electronic engineered components of the powertrain. computers tell this thing how, when and actually learn your shifting patterns depending on the model. something goes wrong with anything in the transmission and you are going to throw an additive in there? This one begs for a logic explanation. It will never pass the commn sense test with me unless it is sanctioned by the companies who build these transmissions, the SAE and API.
How many times have mechanics seen additives in engines and transmissions opened up for a rebuild?
By the way. Think about this. Warranty companies will always love it when you throw additives in the power train. Why? Because if you seize the engine or transmission the first thing they will do is run an oil sample. If it fails you could be shorted the warrant. Trust me on that one.