>>>>I get c. 100 miles out of the 1st 1/4 tank, so I think "Great, it looks like I'll get 400 miles out of this"
>>>>By 1/2 tank the trip odo reads c. 150 miles, so I think "Not so good, but it looks like I'll get 300 miles out of this"
>>>>by 3/4 tank gone it may be c. 210 miles, so I think "Well, I should get 280 miles"
>>>>
>>>>But the low gas bing-bing comes on at c. 237 - 247 miles and I usually have to refuel at c. 265 miles (this is mainly all urban - I get 300 miles on the motorway).
>>>>
>>>>Anyway, what gives? Does this mean it pays to keep your tank over 3/4 full all the time? I doubt it.
>>>
>>>
>>>But of course! You just did the math. An exhaustive, scientific, top-notch experiment. Of course, I would say instead that it is just the inaccuracy of the sensor and needle system, but that's just me. :-)
>>
>>You should keep your tank partly filled so you don't waste fuel hauling around fuel.
>
>But I've always felt that a car runs better with a fuller tank - maybe just imagination but others have agreed with me. One could argue that at speed the fuller tank gives you a better momentum (not going up hill of course) once you're up to cruising speed.

Its all perception really. My car runs better when I'm in a good mood.

the end logic of your statement would be to make the car as heavy as possible. In the US you could keep all your guns in the boot :-)