What fuel additives are available to decarbonise / decoke an engine?
There are no addertives that will remove hard carbon from valve heads; not even Redex will do this. When an engine is in need of a decoke the carbon is built up on the valves to such a extent that it obstructs the flow of fuel in to the engine – the heavy carbon build up would be on the inlet valve, the carbon would actualy take the shape of the port and would look like it had been machined. The only way to remove this was to remove the valves from the head.
The old favourite Red-Ex is still available. There is also a specific product whose name escapes me that is in a tube and you warm the engine up, remove the plugs, put some this gunk in and leave for 30mins. Then restart the engine and run it for 30mins. I have never used it myself but have seen it used and when restaring the engine it produces huge clouds of greyish smoke for some minutes. Whether it actually does what it says on the box is open to debate. Most modern engines actually produce very little carbon deposits and a ‘de-carb’ is almost a thing of the past now.
