I am at 25k on my car now (2014) and I just realized (really late, my fault) that skyactiv is a direct injection engine. So what are you guys doing to combat the carbon-on-the-valves issue? I read that every 20-30k they need to be cleaned. But I'm not so sure about the chemicals on the marker (snake oil?) that you just spray into the intake. Is it better to take it to the dealer?