for the 1000th time, lets go over it again.
The engine is a system and as such you can't look at something as simple as fuel doesn't directly see the intake valves to wash off deposits. Lets start at the beginning, the injectors:
- DI fuel injectors operate at MUCH higher pressures than traditional injectors. They are also more prone to fouling from deposits than traditional injectors.
- When DI injectors foul, the spray doesn't atomize properly.
- Without proper atomization of the fuel spray, the combustion within the chamber becomes less complete than normal which means more fuel left over in the combustion chamber.
- The excess, unburned fuel ends up seeping into the oil.
- Fuel in the oil leads to increased volatility of the oil.
- Increases in oil volatility increases oil vaporization.
- INcreases in oil vapors then increase the flow of vapor through the PCV system.
- This increase in oil vapors through the PCV increases the rate of intake valve deposits.
So, in order to help PREVENT, SLOW DOWN and/or minimize intake valve deposits, fuel system cleaners are HIGHLY recommended, even by auto manufacturers. Keeping injectors and combustion chamber cleanliness is the first step in prevention.
Also, intake injection cleaners (seafoam or similar through the intake) do NOT clean intake valve deposits. Those cleaners clean up soft gummy deposits but not hard ones like found on intake valves. THere are many tests around the internet where you can see pictures of such tests. BG claims to have a multi step process but it is much more complicated than just using a vacuum tube.