Re: Fuel additive (vfr31)
Gasoline is itself a solvent that is formulated with detergents to keep your injectors and fuel system clean under normal driving conditions. However when you shut your engine off, fuel system components that see direct heat from the engine, bake the fuel causing buildups of waxy, tar-like deposits. When you restart, the gasoline again acts like a solvent for these deposits but over time they can build up, especially if you tend to take mostly short trips. After about five years/50,000 miles they say that you can expect your injectors to be 10-20% clogged, even if you regularly add an injector cleaner to your fuel. Deposits elsewhere, such as in the throttle bodies, is usually of no concern unless they cause some sticking of the butterflies.
The tiny orifice of a fuel injector nozzle is the most susceptible to fuel system buildups and contaminants such as rust or fuel line particles that make it past your fuel filter or are introduced during repairs. The injectors always have to be removed in order to remove any foreign bodies. Such injectors dribble fuel out, and show asymmetrical spray patterns that reduces fuel vaporization and consequently engine power. An injector should spray a fine mist.
Injector cleaners contain chemicals such as toluene (normally found in gasoline at lower concentrations) that need to be diluted with fuel to avoid damaging fuel hoses and o-rings. So, even if used regularly, these cleaners won't remove tough deposits in low-flow areas. Further, these cleaners can damage expensive oxygen sensors and catalytic converters. Professional cleaning services remove the nozzles anduse ultrasound equipment to scrub the deposits off. This technique vibrates the injector (while it pulses) with ultrasound waves that then breaks up the accumulated deposits.
The most common problem with injectors is they accumulate a buildup of inside the injector and on the pintle/seat area. The injectors are manufactured to such close tolerances that a 5-micron buildup (a human hair measures about 70 microns) will reduce the flow up to 25%.
After 50,000 miles worry about it ...
