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Auto Fuel Additives

by Bob Hagin

July 23, 2001

In the old days (and maybe even during these "enlightened" times), medical quacks sold unwitting and sometimes desperate people concoctions that contained everything from cocaine to snake head extracts. This lead to the expression "snake oil" for liquids that could cure anything that ailed the buyer.

We can also include in this category automotive products that can revitalize a sulfated battery or grow metal back on piston rings, engine bearings and driveline gears. One even promises to coat combustion chambers with platinum by spraying a liquid into the intake system.

But there are automotive chemicals that can be helpful to car owners and they collectively make up a multi-billion dollar annual business. They fall into the following categories:

BOOST OCTANE - At one time you could buy 120 octane gasoline from your corner station and in the '60s, we needed it. Developing high horsepower in those Muscle Car days meant relying more on hot-rod "tricks" than on high technology and to avoid pinging and detonation, those engines needed a diet of high octane fuel. Back then, high octane ratings were achieved by "lacing" lower quality gas with tetraethyl lead, a chemical that slowed the burn rate and allowed it to be used with those high compression engines. In the development of add-on pollution control devices that appeared in '75, it was found that tetraethyl lead coated the interior of the catalytic converters, made them inactive and eventually plugged them tight enough to blow out. But there's still lots of aging high compression engines around that find that even the highest octane fuel available makes them knock and ping. Chemical octane boosters are available from auto parts stores and can boost the octane rating of "pump" fuel by as much as seven points, but it's not cheap.

CLEAN COMBUSTION CHAMBERS - If high compression isn't causing that power loss or pinging in your late model car, and all the other engine management aspects are OK, another cause may be excessive carbon build-up in the combustion chambers. The carbon takes up space in the chambers (as well as around the intake valves) and the volume of the combustion chamber is decreased. This raises the octane requirement of the engine. Another problem with carbon build-up is that it gets hot, glows red and indiscriminately sets off the incoming fuel charges too early. It can even cause the engine to "diesel" (keep running after the key is shut off) which is very hard on the mechanical parts. One cure is to take off the cylinder head or heads and remove the carbon the hard way, but the automotive chemical guys have a better (and cheaper) idea. It's a concoction that's poured through your engine's air intake while it's running at a hot, high idle and it burns off the carbon. It's fairly cheap, at around five dollars a can. Unfortunately, this can upset some of the engine controls on some modern engines, so there are there are even more exotic cleaners that you can run through the fuel system itself to clean out the combustion chambers as you drive.

FUEL TANK WATER REMOVER - In some of the old World War II movies, haggard and hassled tank commanders and flight crews referred to "watering down" fuel to make it go further. But water and gasoline don't mix, right? Well, not very much but enough to do some damage if there's too much in your fuel system. About 2000 parts water per million parts of gasoline is a rough "mix" number and anything over that drops into a little "catch" cavity that you may find at the bottom of your fuel tank. The water gets into the tank as water vapor that's in the air which is pulled into your tank to displace the fuel as it's used up. A chemical fuel system water remover poured into your gas tank mixes with the water as well as with the gasoline and the resulting solution is pulled into the engine and burned. It's cheap (only a couple of bucks per bottle) and the suggested dosage is 12 ounces in 15 or 20 gallons of gas.

"TREAT" THE GAS - This is a kind of "catchall" name for the usual light aromatic solvent naphtha blends and I suspect that the main difference between them and most of the other chemicals listed here is in the marketing. Regular use (usually recommended with every tankful of gas) will no doubt keep the water problem at bay and keep the fuel injector nozzles clean, but the recommended dosage will also increase the cost of that tankful.

CLEAN CARBURETOR AND ENGINE PARTS - There are no new or late model vehicles that use carburetors, but there are lots of older cars and trucks around that still use them. My daily-driver pickup is one of them. "Carb" cleaner is the common-usage name of that's attached to these pressurized cans of degumming fluid, but the labels now read "Parts Cleaner." I've used it to not only clean out choke and carburetor passages but to de-gum P.C.V. (positive crankcase ventilation) valves without taking them off the car as well as to find vacuum leaks in worn or split hoses or on loose carburetors and intake manifolds. Their long, thin, detachable "snorkel" tubes come in handy for precise spraying. It's mixable with water so it can be used as a drying agent on ignition parts that get wet. I always keep a two dollar can of it in my toolbox.

Automotive engine chemicals are useful but none of them are miracle elixirs. Remember: if the claims made by the manufacturer sound too good to be true, they probably are.