Confused about my MPG

[logic_guy]

Yesterday i drove from Here to Cockfosters Tube Station.

I filled up £18 and i already had some fuel in the tank. This bought the fuel gauge very nicely up to the half way.

I took the A1m all the way and drove at a steady 80Mph (Maybe 85mph when i was going down hill )

I have a VTS gearbox, so i was doing 4,000RPM all the way and the journey is a total of 101 Miles. (50.5 miles each way). I got home last night and went to turn the ignition off and notice the petrol light is on.

I've herd people getting 100miles to £10. I've worked out my MPG is roughly 25Mpg on this trip, I normally get 40Mpg or even 50Mpg most other times on similar trips (IE, trip to London the other day).

A full service was done probably 3K ago.

Any suggestions why this run was very bad? Even though i was driving steady.

[devilsadvocate]

I think you are adding up wrong

£18 of fuel
101 miles
Say £1.36 a litre

Makes about 35mpg

£20 gets me about 110 miles of motorway driving and that's sticking to 70-75mph

[logic_guy]

Originally Posted by devilsadvocate

I think you are adding up wrong

£18 of fuel that i filled up, and probally another £5 worth of fuel in the tank and it was on the orange light ~£23 of fuel in the tank
101 miles
Say £1.36 a litre

Makes about 35mpg

£20 gets me about 110 miles of motorway driving and that's sticking to 70-75mph

I Don't think so?

£23 of total fuel in my tank = 17L of petrol.
17L of fuel in the tank over 101 miles = 27.01Mpg

Edit. 27L of fuel would mean i have a bone dry tank, which i don't. I've got the red light on, so maybe used 25L of fuel = 18Mpg.

Please correct me if i'm wrong lol

[devilsadvocate]

Make the red light come on
Fill the tank right to the brim and record how much you put in
Wait until the red light comes on again and record the miles you did

Then work out MPG

[logic_guy]

That's how i normally do it. I can normally almost get 400 miles to a full tank of fuel and i know roughly how far i should get with the 2nd half of the tank. Is it me or is the 2nd half of the tank seem to go quicker then the 1st half?

[Tc24]

Probably just where you parked - I can gain over 1/4 of a tank depending on where I park because of how the fuel level sensor in the tank is Try moving the car somewhere else, and the fuel light will probably go off again for a good while.