Oil Change Is A Must, But How About Some Fuel System Cleaning?


Apr 15, 2001 (Updated Apr 23, 2001)


The Bottom Line You don’t have to wait till you experience knocking and significant loss of power to understand your engine needs some cleaning.

You probably heard it hundreds of times – “The oil should be changed every 3,000 miles” (the mileage depends on car and driving conditions). OK, how about your fuel system?

Although the gasoline contains cleaning agents, the deposits still tend to accumulate in the car’s fuel system. It is especially affecting old cars, which tend to accumulate deposits in the combustion chamber, fuel injectors, valves and other parts of the fuel system.

The accumulation of deposits in the combustion chamber increases the compression ratio and the clogged fuel injectors along with valves with deposits can create a lean air-fuel mixture, both of which lead to detonation/knocking, loss of power and increase in the fuel consumption.

Although some of the symptoms sometimes can be cured by switching to a higher grade of gas, there is a better long-term solution – products that clean the fuel system.

My second car, 1988 Volvo 740 GLE, started knocking recently. Under part to full-throttle it sounded like a go-kart. It also had less power than it used to. Suspecting that the problem is in the fuel octane rating, I filled it up with premium 91 octane. Knocking did not decrease at all. Even if it helped, it would be an expensive and only partial solution.

Note: I always use “regular” 87-octane gas in this car, as the manual suggests. Since premium gas didn’t help, I went to Target and got a “Complete Fuel System Cleaner”, hoping that it will solve the problem.

Be aware that there are products that clean the entire fuel system, including the combustion chamber, valves and fuel injectors, like the one I got, and the other ones that only clean fuel injectors (and cost several times less). If you have problems of the magnitude I describe, don’t try to save money – get the product that will clean the entire fuel system.

I used cheap fuel injector cleaners before and didn’t really see any effect. The product I got was produced by STP and cost about $7. And it really made me happy – the knocking disappeared, the car no longer feel sluggish and I can still use regular gas with no problem. Another case of “You get what you pay for”.

As the sticker on the bottle said, it is recommended to use this product once every 12,00 miles and the fuel injector cleaner once every 3,000 miles, so I will probably do so. And the fuel system cleaner I used cannot be used more frequently than once in 4,000 miles, which is a good indication of its effectiveness.

You don’t have to wait till you experience full-bore problems like knocking and significant loss of power to understand your engine needs some cleaning. If you feel that you don’t have the power you used to – you can get a fuel injector cleaner for $2 and see if it helps.

Keep in mind that the knocking can be caused by the wrong ignition timing and other factors, so if the fuel system cleaning doesn’t help, you might have to visit your mechanic.

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