[Phil №❶]

Does anyone know what form of guesswork the computer uses to calc l/100k. The car said 5.8 l/100, after filling, my calc was 6.949. The car is always brimmed, so I simply replaced the real fuel used for the given distance.

Here are my figures from today's fill.

739.2 ks $77.31 @ $1.505 / lt = 6.949 according to me.

There is no excuse for a variation like that in a modern car IMO.

Driving up or down hills alters the instantaneous figures, so the computer is obviously getting fuel flow info from somewhere, so why isnt, it accurate.

[Dazzler]

Geez.. looks like someone got out of their car on the wrong side of the garage 

Never seen the i30 trip computer out more than a couple of points if zero'd in line with the trip 

[Phil №❶]

It's always zeroed at each fill.

[AlanHo]

I suspect that gross errors are the result of not filling the car completely to the brim each time. If you rely on the pump clicking off - even after a few clicks - you cannot be sure the car is absolutely full.

I brim my car until the fuel is visible and stationary in the filler neck -almost spilling over. It takes at least 10 clicks of the pump and takes me a good 5 minutes to refuel. That's why I refuel early morning when the service forecourt is empty and I then don't get impatient stares from drivers kept waiting.

This is my spreadsheet - you will see that I have added a column showing the actual fuel calculation increased by 2.5% - having checked the accuracy of my speedo odometer against motorway kilometer boards over a distance of more than 100 Km

[Phil №❶]

Sorry, Alan, but I do exactly the same thing, filling till the liquid is static at the top of the filler neck, so that's not the answer I'm afraid. 

Nice spreadsheet you've got there, I have one also which highlighted this initial variation.

[rustynutz]

Phil, me suspects a little chippy is messing with your pooter....

[Phil №❶]

This could be possible, but if the fuel injection timing is all that's modified, then the amount of fuel flowing through the fuel line should reflect any changes accordingly. I don't mind which way the L/100 shapes up with or without the chip, but i'd prefer the pooter to be accurate. You wouldn't want to be crossing the Nullarbor using the car's displayed info. Could be embarrassing. 

[Dazzler]

but i'd prefer the pooter to be accurate. You wouldn't want to be crossing the Nullarbor using the car's displayed info. Could be embarrassing. 

I'd still rather be in a Diesel i30 than anything else (apart from my Hybrid maybe) I suspect your DTE would still be conservative 

[Alasama]

The cycle of trip computer calculation is around 20 seconds (even stop at the red light). Average consumption will be based on these readings. The most obvious timing to see it is:

Every time I re-set the average consumption figure when re-filling the tank, then I saw the reading changes around every 20 second while driving out of gas station.

If didn't re-set the trip computer, it calculated by all the existing readings and old data. In this case, this reading did not represent the single latest tank status.

[Lakes]

but i'd prefer the pooter to be accurate. You wouldn't want to be crossing the Nullarbor using the car's displayed info. Could be embarrassing. 

I'd still rather be in a Diesel i30 than anything else (apart from my Hybrid maybe) I suspect your DTE would still be conservative 

never checked acuracey of the trip computer. but my first i30 crdi got 1,100 per tank full not worrying how i drove, this one gets 1,100 1,200 per tank full not worrying how i drive still. i'm not worried i know what i can do on a tank full. when i really tried on my first i30 i got 1,300 from a tank full. Bob Ouri30 got 1,400 from a tank full so did Thumper.
my i30 CRDi uses less fuel than my Harley Davidson Motor Bike so can't complain as the bike runs on 98 octaine