I do not think that all fuel injector and fuel system cleaners are "snake oil", but agree most are are. In the U.S., the Chevron Tectron products have shown to be effective in tests, and I have had good results with them.

I think Elrings's problem relates more to where he lives, the fuel he gets, and the fact that there really are no freeways around Stavanger to "blow" the carbon out of his car. I suggest a road trip! Oslo..or mid summers night on the Black Sea in Sweden? Or if not, maybe see if you can get down on the Sola Airfield and race around a bit!

It was very common for Older American Cars that were not driven far, or at any great speed to become "carboned up". My Grandmother drove her 1951 Plymouth no more than eight city blocks per trip, to a total of 31k miles in slightly over forty years. It had to have the head removed twice to have the carbon from the pistons and head surfaces removed. I have the car now...34k miles...and it still lets out some puffs of black soot now and then.

The best additive that gets to carbon deposits is adding alcohol to the fuel system. In the U.S., the cheapest form comes in something called a "gas dryer" that is sold in the winter months to remove water from the fuel system. It also will help with the carbon. It costs about $1.20 per bottle in the U.S. I would put two bottles in per about ten gallons of gas, and then hit the freeway. Since you do not live by a freeway, you will have to get by just driving...but this will help. Might take doing it for several tankfulls, but you should see some improvement. Remember to make sure your plugs are clean first, and to keep an eye on your oil...if you really have some deposits, some of it will end up in the oil and it will get dirty fast...so remember to change it.

In the U.S., carbon is not much of a problem anymore, because during the winter months since about the late 1980's or so, the US Oil Companies have added alcohol to their fuel mixes at about a 10% rate. While we are supporting our Mid West Farmers by this addition of "corn/grain alcohol" in our fuel in the winter and getting our carbon deposits "cleaned" in the process, I am sure you are getting the strait stuff from the North Sea at your local StatOil Station. That means a good shot of alcohol in your tank might be just what you need.

Good Luck!