Over time, the internals of your engine get clogged up with all kinds of nasty stuff. Inside the crankcase, where the oil lives, varnish and tar build up on the surfaces of the pistons, rings, lifters and in the oil galleys that supply the oil to all the components. This lowers the engine’s ability to cool and lubricate itself, reducing the efficiency, performance, and life of the engine.

The same build up occurs inside the fuel system as well, clogging the injectors or carburetor jets, gumming up the intake valves and on the tops of the pistons too. If the valves don’t move freely, then your engine’s breathing is greatly hampered. Carbon deposits on the pistons and valves can lead to hot spots which cause detonation, which lowers your engine’s performance. The trick is how do you clean? Virtually every engine, from 2-stroke lawnmowers to big rig diesels face the same problem.

Sea Foam has been around for over 70 years, and it is one of the most trusted treatments for all engines. While Sea Foam makes a range of excellent products, the main one is Sea Foam Motor Treatment. Sea Foam is specially formulated to safely and slowly re-liquify the gum, sludge, varnish and carbon deposits from the hard parts in your engine so they can be flushed out of the system.

Sea Foam helps lubricate the moving parts, particularly in the fuel system. Ethanol additives dry out the seals and leaves a varnish that makes it harder for oil to lubricate the parts. Removing this varnish brings the engine back into top working order. Inside the fuel tank, Sea Foam absorbs water, allowing it to be burned up in the combustion chamber without issue.

Sea Foam Motor Treatment can be used three ways- in the crankcase, in the fuel, and in the top end of the motor via vacuum lines.

In the crankcase – When added to the oil, Sea Foam will clean up sludge, quiet noisy lifters, and remove oil varnish. One can treats 10 quarts of oil so you get 2 treatments in one can for most vehicles. The best method is to add the treatment 500-1000 miles before the next oil change, and then add the rest after you have changed the oil. This will get the big amounts of varnish and sludge out, and the second treatment keeps things clean.

In the fuel – One can treats up to 25 gallons of fuel. This will remove deposits from the fuel pump, injectors or carb jets, control moisture, and stabilize the fuel. In diesel engines, it will de-ice and has anti-gel properties.

Top-end introduction – By feeding 1/3 of a can into the vacuum line, Sea Foam will clean the intake valves and pistons, restore power, and remove carbon and varnish residue. The first two uses are relatively easy, you just pour it in and drive. The top-end introduction is a little more tricky. Start by locating a vacuum line. For most vehicles, the power brake boost line will be the easiest. It is vital that the line services all cylinders, so it should be located at or near/under the throttle body or carburetor. Remove the line from the accessory (not the engine side), and start the vehicle.

Insert a small funnel into the line. The car will be running rough due to the missing vacuum line. Slowly pour a little Sea Foam Motor Treatment into the funnel. This will take some time. You do not want to put the vacuum line directly into the can or just pour a large amount into the funnel, this can cause hydro-lock inside the engine, which is very bad. Pour in 1/3rd of a can.

Turn off the engine and let it rest for at least 5 minutes. After the waiting period, start the engine and let it idle or take it for a spin. Be sure that the exhaust is properly ventilated, as the exhaust will be a dense fog within a few minutes. Once that passes, the treatment is complete.

Treatments like this may seem complicated, but with a little bit of prep work, you can do it yourself and restore your vehicle’s power and performance. If you have any concerns, stop by your local NAPA Auto Parts Store or NAPA AutoCare Center.

Source: knowhow napaonline com/sea-foam-what-is-it-and-why-should-you-use-it/ NOTE: PUT A FULL STOP BETWEEN THE SPACES AND CLOSE THE SPACES TO ACTIVATE LINK

It's actually used for de-carbonizing. The process should be strictly done by a good auto mechanic or a DIY enthusiast. If not done properly, the car engine might HYDRO-LOCK. The processes can be used in place of having to strip the car engine and de-carbonize manually. Heard its quite efficient when it comes to de-carbonizing.

I thought the myth on sea foam has long been busted.