Engine cleaners

Q: Hi Greg. I came across an old article you wrote about removing carbon buildup from an engine by pouring a top engine cleaner down the carburetor while idling. That’s a drawback of modern fuel-injection engines: The only way to add an engine cleaner is by pouring it into the fuel tank.

I always used Redex to de-carbonize, and the directions on the can (U.K. version) stated that after pouring most of the fluid into the carburetor, the engine was to be shut down and the remainder was to be poured into each cylinder via the spark-plug ports. These were then plugged with rags and left for about 30-60 minutes. Then the rags were removed and the engine turned over without the plugs installed to expel excess Redex. This was best done by having an assistant loosely blocking the ports, otherwise you would have Redex dripping all over the hood and elsewhere.

It also advised that this job should be carried out in an open area away from houses etc., due to the clouds of gray/white smoke that were produced. Would you recommend that this part still be done with modern engines, or just stick to adding it to the fuel tank? — Alistair D., New Port Richey, Fla.

A: Alistair, thanks for your interesting letter. Who could forget those clouds of smoke pouring out the tailpipe? As for Redex, I’d follow the manufacturer’s instructions for best results, but there are numerous fuel additives to choose from that are much easier from a labor standpoint.