SPT

How do you know you are nearly getting to the bottom of the tank?

Easiest way to calculate your mpg - fill her up to the brim and reset your odometer - drive until you need to fill her up again. see how many gallons you need to fill her up again to the brim. note down mileage on odometer.

divide mileage by gallons and theres your best answer.

If you are still getting 22 then theres a problem somewhere - unless all your driving is short trips or all urban driving....

Hi Mark. Yes that's exactly how I am calculating it. SPT

I bought my Rx400h 4 months ago from Lexus hoping to get as close to 34 mpg as possible. I have filled up approximately 16 times and average 320 miles per tank. This means my actual miles per UK gallon is 22.3. (320 miles divided by the 14.3 gallon tank). However my vehicle display is telling me I am getting 29 mpg, which clearly I am not. I am surprised the vehicle computer is incorrect. The only possible reason is that I still have quite a lot of petrol in my tank when I fill up, but I feel I am running it down to almost zero (to see how many miles I can get out of it). If I were getting 29 mpg then it would be okay, but Lexus sell on the basis of 34 being achievable and the on board computer says 29, but to only be getting 22 feels wrong. I spoke to my Lexus dealer from whom I bought the car and they said "the car is fine and working normally" and that "the on board mpg figure isn't what mpg you are getting, but what mpg you could be getting if you adjusted your driving style". Again that feels wrong. Surely an on board computer can measure how much petrol is being consumed and how many miles are being driven. Has anyone else monitored their "actual" mpg or got any thoughts/comments....?? Many thanks SPT.