400km sounds quite a bit low...
I usually fill up around 14-15 gallons (53-57L), have gone past 16 at times. Keep in mind that 68L is probably the entire fuel system, not just the tank. When i'm past 15 gallons, that usually means the computer is already blinking (not showing remaining range) and the gas needle is below "E"
Although it does seem there is some left to go on.
400km though... that is low... that's about 250 miles... while I normally get 350+ easy.
Here is a link to my 130 fillups since I bought the car:
http://www.fuelly.com/car/infiniti/m35h ... luk/443578
by the book the car should be 29MPG on average...my average is around 25MPG. have i gotten 29? yeah, a couple of times but not regularly. If you look at history of my MPGs, you will see that winter does suffer, however, things I did notice.
- lead foot = kills MPGs, and this car is easy to drive a bit harder. It is a heavy vehicle, and city acceleration kills it.
- sport mode = kills MPGs, but it is soooooo much more fun
- I did get good results with ECO mode, but only used it on maybe 10 fill ups and it just gets a bit annoying sometimes, but makes a difference.
- This car shines in nice weather on a highway going the speed limit, easily 30+mpgs, just can't go 65 on highways in Jersey... you will get run over.
- AIR FILTERS!!! I actually did notice drops in MPGs as my filters age... check both of yours.
- this last one... no personal experience... but... tires... lower resistance tires vs more aggressive, they could have more resistance, thus higher gas mileage... this is strictly based on TireRack tests though, and not really on our specific vehicle or any specific tire just a general comment, but could easily account for 1 MPG
On a plus side... I did drive m37 for a bit... I was averaging 17-18, if not for M35h, I'd be looking at M56... and I can pretty much estimate that I would be at 16-17 (based on my driving). To me hybrid made sense.
Reference: 29MPG = 8.11 Liters per 100km
25 mpg = 9.41 Liters per 100km