I have used the CRC GDI cleaner and can tell you that is absolutely does not work, at least on a Porsche V8. I had the intake off to replace the starter and noticed the intake valves are pretty well covered in a thick layer of carbon. Car has 100k on it. I did not have the CRC cleaner at the time so I put the car back together after replacing the starter, leaving the valves as they where found. About 2 weeks later I got some of the CRC cleaner and followed the directions exactly and hoped all would be ok. Another month or so later, the vacuum pump went out and in order to access it, the intake has to come off again. I checked out the valves while the intake was off and there was absolutely no difference in the appearance of the valves. The car uses maybe one liter of oil between services (10,000 miles) Save your money and if you want clean values, walnut blasting is the only way to effectively remove the carbon.

 

‘’Sorry. Wrong thread