I was watching my mpg display (which is surprisingly accurate) And Just got sick of seeing 16.5-16.8mpg. And I`m thinking to myself, what the Heck`s wrong with this thing, it never drops below 17, which is bad enough. I had Castrol GTX 5W-30 in it,and decided to dump it early and put in the Mobil-1 5W-30 I had bought a few months ago. Well almost instantly the read out started rising and has now settled on 17.5....Just like that! From 16.8! and no difference in driving style, weather conditions/temps, same tank of fuel, route etc. And I forgot just how smooth the motor is on the Synthetic. Sooooo, Looks like I was wrong (in my case anyway) to change from the Synthetic in the first place. (blush) Moral of the story, lesson learned.

 

I thnk it has someting to do with the winter blend fuel too????

 

Winter blend fuel will make mileage worse, not better.

on the other hand, i have used Castrol since i bought my 2004 about 3 years ago, now tempted to try it on synthetic

 

I switched to a 0W/20 Synthetic and MPG has been pretty steady. I gained about 2mpg peak when diving lightly which is about 32 mpg on the tank. I get 25.6 AVG driving with a heavy foot now as opposed to 24.1. This is on the 400h though. I'm sure you could realize the same 2mpg gain with the 330/350.