I have just done the same Dr Zoidberg..same mile..same refuel qty. But my mpg on trip computer showed 51mpg not the 54.5 that the maths came up with!

Sent from my GT-I9100

Mine always does better than the maxidot is actually showing...

Makes a change from my 7% optimistic bravo.

I'm pretty sure you don't want to run a diesel dry. It could possible ruin the engine.

I'm pretty sure you don't want to run a diesel dry. It could possible ruin the engine.

No it'll be fine, they even self prime these days. The main reason not to run it dry is you'll look a tit

I've rand mine to the bottom of the red with the range showing zero and still only managed to get 46 litres in so the gauge isn't close to accurate, worst I've had in any car.

No it'll be fine, they even self prime these days. The main reason not to run it dry is you'll look a tit

I've rand mine to the bottom of the red with the range showing zero and still only managed to get 46 litres in so the gauge isn't close to accurate, worst I've had in any car.

 

I've filled up several times and 46 litres is the most I've managed! A 7 litre reserve is pretty huge but when I calculate my MPG using 43 litres instead of 50, my MPG tallys with the trip computer....so now I'm happy.

 

Still, 52 MPG is nowhere near the 74 MPG figure in the blood brochure. I wasn't silly enough to think I'd every 74 but I thought I'd be hitting at least 60!!!

15k miles in, hitting 58-61mpg reliably. Set to Eco, a/c off, normally me plus 1, 30 mile rural A roads journey, a few roundabouts, no bad traffic. The short bits I can use cruise I am at 53-57mph, rarely stray above 60.

To answer a couple of slightly off topic questions:

 

On modern common rail diesel engines it is usually very harmful for the fuel pump to run out of fuel.

Therefore manfuacturers will add protection which will stop the engine before you run out of fuel (hence just filling up again & the engine will run - no priming is needed because there was still fuel in the system).
These system can involved switching off an injection every now and then to make the driver feel like its running out of fuel & encourage them to fill up soon.

 

For speedo's there are different requirments in different countries for the tolerances of "indicated speed".
In the UK it usuall displays ~10% under the real speed (hence the difference with some SatNavs which display "real" speed)

As AndyVee says, the car does know the "real" speed an uses that internally for all calculations.

 

Fuel Tank Display is a difficult  choice for manfuacturers. Do you display the "real" level as best you can or a "underestimate" so people dont have problems.

Its also not that easy to measure small quantities of liquid in a large horizontal space.

E.g. here in Switzerland it is illegal to run out of fuel on the highway (you will get a big fine & possibly a short ban for repeat offenses).
However, 7L reserve does seem about twice what I would expect & adding 40L when it says empty or >50L does seem strange..!

The fuel gauge in many cars I've owned has not been linear. e.g. The top 50% runs down very quickly, then next 25% a bit slower & the last 25% probably has doulbe the mileage you think.

For me this is always something you get used to when you own a car for a while.
 

The speedo should read over the real speed not under it.....

It's also illegal in the uk to run out of fuel in the motorway.

Neily03, on 13 Mar 2014 - 09:56, said:

The speedo should read over the real speed not under it.....

It's also illegal in the uk to run out of fuel in the motorway.

 

I'm pretty sure that there is no such law re running out of fuel on a motorway....willing to be proved wrong if you can find me the act and section that says it is so? I understand that it might be illegal on an autobahn but not in the UK...

Edited 13 March, 201412 yr by bouff34