back when lead was available in fuels, that was a lubricant property in fuel and it helped, but now with unleaded fuels lubrication from fuel is minimal. many gasolines contain unstable components that can lead to deposit formation in high temperature areas in the air induction system such as carburetor, throttle body injector (TBI) or port fuel injector (PFI) or at the intake valve stem where the fuel flows through to the combustion chamber. since 95 the epa has mandated the use of detergent additives in gasoline to reduce emissions, but when you induce detergents, you reduce lubrication, so what lubricates the vavle stems and valves, and keeps the deposits from carbonizing up, on injectors and around the rings, causing sticky rings? this is where you would need a good balance from a fuel additive that can clean but yet also provide a lubricant to help reduce the wear created as mentioned above. also, without a good top end lubricant, you can experience valve recession among other things.
now in diesel fuel, you have sulfur as a primary lubricant. when epa reduced the sulfur content of diesel, alot of the engine manufactures had all sorts of leaking seals from their pumps because they were lubricated from the fuel and such as some of you may well know, that created alot of problems.
now adays, this isn\'t really a problem, but still there is the carbonization that is created due to sulfur. ever saw an injector or glow plug just carboned up with a black brittle substance? this is due to sulfur compounds burning to form acidic by products.
here is picture of a small test to show how a fuel additive reduces sulfur and neutralizes the acid by product of the fuel.
the one on the left is without the fuel additive, and right with the additive.
what i did was to take 2 tubes, filled both half way with the same diesel fuel (note, don\'t attempt this with regular gas!), added 3 drops of sulfuric acid (byproduct of sulfur after burned) in both tubes. added additive to one on right, then shook well. then i drained them, and with a little torch, i heated them up and this is the result i got. as you can see, the one with the additive dang near eliminated the carbon that i have on the left one. this alone will affect your fuel mileage, performance, and help prevent rings from getting carbon deposits and sticking.
another problem, water content. all diesel fuels contain small amounts of water. as temperature decreases, the amount of water dissolved in the fuel will also decrease and may lead to a water layer forming on the bottom of the tanks, which in turn can cause bacterial contamination, added to water, will /can cause corrosion, filter plugging and icing in winter.
now, alot of fuel additives are subject to do one thing or another, but when looking for a good fuel additive, you want to find one that can address all these problems in one. so read the fine print, some are nothing more than an octane or cetane booster. others just a cleaner. what you want is one that clean and lubricate, the performance will increase once you address those two problems.
conclusion: yes, i use a (schaeffers) fuel additive in mine all the time and suggest the same to others for the reasons supplied above.