Trip Computer: Fuel consumption accuracy by manufacturer/car

[Mr_Sukebe]

Just curious about the accuracy of fuel consumptioon trip computers for your cars.
Over the years, I'd had a few, with the following:
- Mid 80s VW over-estimated by approx 50%
- Volvo S60 D5, over-estimated by approx 10%
- BMW E46 330i over-estimated by approx 5%
- BMW E91 330i pretty much bang on

So how do you find the accuracy of your cars?

 

[Imy]

Both Fords I've had show pretty close to the real amount used but as they only show average mpg over the last x miles and not the mpg between fill ups, it's difficult to compare accurately.

 

[Greebo]

Both my last car, Renault Laguna and my current one, Seat Leon both under estimate by about 10%

 

[paradigm]

My 2008 A6 under-reads, maybe within 10%, I've not done a manual calculation for a while.

My E46 330d was pretty much spot on.

 

[DanTheMan]

Mk1 Toyota Yaris reads spot on.

 

[GeX]

Fuel computer readings vs brimming tank/miles per tank calculation.
2002 Xsara VTS was consistently ~4mpg over per tank
2002 Renault Clio is consistently ~3mpg over per tank.

 

[rG-tom]

E46 330i was pretty much perfect.
E92 335D under reads by ~1-1.5mpg, regardless of figure.

 

[Raymond Lin]

Toyota Yaris is almost spot on, it's about 2% ish higher than what it really is. Shows 40mpg when I worked out as 38.5 mpg etc.

 

[mattyprice4004]

MG ZT 190+ was always pretty good, a little generous sometimes. Maybe 10% out.

 

[lordrobs]

Octavia over estimates by 5 to 10%.
Grande Punto under estimates by up to 5%.

 

[bledd]

The only electrical luxury my car has is a 12hour clock, so I have to do mine manually

 

[Bennie-Mac]

Current car doesn't have a trip, but my Leon fr diesel did and it over estimated by around 20%. Also couldn't trust the fuel range either. Full tank said 600 miles when in reality you would get 450.

 

[rodenal]

Mines is within 1 or 2% but I was able to manually correct it.

Worst culprits i've had for over reading were my A3 and various focus diesels - reading up to 20% over (the audi was the worst culprit)

 

[[TW]Fox]

Mine is usually accurate to within 0.5mpg.

 

[Uriel]

The trip computer on my Honda Insight ES (2010) reports mpg about 5% higher than actual.

 

[GeForce]

1998 Peugeot 406 2.1TD underreads by 5-10%

 

[Howard]

Mine seems to be about 0.3mpg optimistic

 

[Princey]

My Ford Focus over reads by ~10%. The Monaro well I haven't work it out manually just incase it's actually worse than the computer says.

 

[mattyprice4004]

Mine is usually accurate to within 0.5mpg.

Impressive!

 

[Jonny69]

The only electrical luxury my car has is a 12hour clock, so I have to do mine manually

Pfft. I don't even have a fuel gauge. I have to take the cap off the tank (which doesn't lock, for the record) and shake the car to see how much is left in there

Her 207 gets nothing near the book figure so I have no reason to doubt the trip computer is reading high or low and it won't make much difference.