Just happened to see a YouTube video on how to clean the carbon off valves in a GDI engine. Procedure seemed very involved as you put in 2 different cleaners, use a brush, take out the spark plugs, and let the first one soak for 30 minutes and then vacuum the stuff out (twice). Must cost a couple of hundred dollars in labor for all that. My question is does our 2014 Kia Forte with the 2.0 GDI engine need that? It runs fine at 38k and is doing 39 mpg on the highway and doesn't seem excessively noisy. So far it has had one fuel system treatment when I let the dealer do the 15k maintenance and they did use some type of fuel system cleaner although I'm not clear exactly what it was. I'm sure it wasn't what I saw on the video because they didn't charge that much for it. When our car came to the 30k maintenance, I took it to an independent shop and they didn't do any fuel system treatment it because it would have been an additional amount of money (at least $50) and I didn't want to pay the extra money. Question is should I have? Do these engines need to have the carbon cleaned off the valves at any particular interval? All responses will be welcome. If they do need carbon cleaning, what products are the best? That BG one seems awfully complicated.