Apples to oranges. There is NO comparing a manufacturers ENGINEERED specific blend of additives and some snake oil being thrown in after the fact throwing the ENGINEERED blend of additives. Again, it is a SPECIFIC DESIGNED BY ENGINEERS blend of additives in PROPER amounts that WORK TOGETHER.*I've never understood that either, because you cannot buy gasoline or motor oil that is free of any additives. In fact, they are LOADED with all kinds of additives, as much as possible without just exploding the price of the products.
Some additives DO NOT work well with others, some, in ratios BEYOND what the ENGINEERS developed can cause problems
A good analogy is cake batter, follow the recipe and it comes out great. Eggs make a cake moist, add a few extra above the recipes instructions and now you have a gloppy mess.
Soooooo cruising at 4500 rpm could get me better mpg then under 3000................r-i-i-i-i-i-ight! <rolls eyes>I can only speak for my experience with two Souls. Both show improved MPG on the computer after WFO runs. Keeping your car under 3000 RPM will not guarantee good MPG. But in my experience, romping on it a few times per tank does improve MPG.
Believe what you like. Carbon and general crud DOES build up on the intake valves. That occurs on some GDI mills more than others. VW seems to be the worst. H/K seem to have done pretty well in minimizing it. But I stand by my statement, I have observed it countless times over several years.
The carbon and 'general crud' build up on GDI engines occurs on the back side of the valves. Run WOT all day long if you want, you aint gonna touch that, it's outside the combustion chamber.