Originally Posted by MBDiesel
I haven't driven any other variable displacement systems (I mostly drive diesels) but the Honda system seems to work well. I can tell when it's activated but only when I try to notice it. Gets that V6 minivan 27mpg highway. Doesn't help city mileage much, but you don't use VCM much in town so the city/hwy spread is bigger.
I have a 2008 Accord with the 3/4/6 cylinder VCM. I don't need the ECO light in the dash to turn on/off to tell when it's switching... it feels like a little kick in the seat when it shifts mode. Kind of like that little bump you used to get with a lockup torque converter.
I find that mine runs in 3 or 4 cylinder mode a lot in town.
The problem a lot of owners of the earlier VCM system were having was with it staying stuck in 3 cylinder mode when it really should've been running on all 6 cylinders. When it does that there's a lot of vibration felt throughout the whole car... similar feeling to an out of balance wheel.
A number of owners have also experienced excessive oil consumption along the lines of a quart per 1000 miles. That issue is centered (I believe) on the #2 cylinder which is one of the deactivated ones when in 3 cylinder mode. There is a class action settlement in place where Honda is now offering a short block replacement on engines with that condition. In reality, a friend of mine found his replacement engine started to do the same thing after a few thousand miles.
I don't think Honda ever officially 'fessed up to it being a problem with their VCM. All I know is that sometime after the 2010 model year they changed their VCM from a 3/4/6 to a 4/6 only.
I always wished there was a way to deactivate it completely so it always ran on 6 cylinders. That's how irritating their VCM is to me.