Morning folks. Me and the wife had last weekend away, which meant my Octy got a good run. Since i got it i almost always have the computer showing the MPG, cos i'm partially obsessed by it(have been for a while, but now i don't have to work it out - bliss). On the way there i almost got 60mpg, 59.3 to be precise. Really impressed by this, but i've been wondering how accurate the computer is ever since. Anyone on here bothered to work it out?

Regards

Toby

The computer works out the mpg depending on the average mpg since it was last reset, so if you reset it before the journey and drive like a granny you can get unrealistically high figures (I had over 100mpg on my VRS by resetting it and driving it downhill for 10 minutes!), if you leave it for a while it's more accurate.

People on the forum have compared it to measuring brim-to-brim and (in the case of the 1.8T petrol, not sure about the 1.9TDI) once it has got a good average figure, its still optimistic by a couple of mpg over what you're "really" getting.

Going by what another 110 1.9TDI owner I know gets with his car I would say yours is about right - mid to late 50's mpg

There are other factors that need to be considered as well. My speedo reads about 10% over what I'm actually doing, so I'm covering 10% LESS miles than I think I am. Even with those adjustments taking off 10% of my mileage and calculate from the amount of fuel I'm actually using, I'm finding that my trip computer is another 10% on top mpg-wise. So I always allow for around 20% inaccuracy on mine. It's only supposed to be a basic guide anyhow. It doesn't actually have a fuel flow meter, just based on vacuum, revs, etc. etc.

I have had both 1.8 petrol and 1.9 diesel octavias now and both trip computers were no more than 3-4 mpg out so if it's reading 59mpg you can guarantee it'll be at least 56mpg. The crack about 10-20% is unfair to the trip computer it won't be 10mpg out.

That's what i thought. Even if it is optimistic, it can't be that far out otherwise why bother installing it. I've also noticed my speedo over-reading when i use my sat nav. Think i'll work it out properly one day, just like i used to and see how it compares. Still chuffed to bits with my car. So far it's better in almost every respect than my Subaru. Ask me again when it snows....

Toby

Use Fuelly to work out MPG if you really want to see how you're doing.

Just jot down your current mileage on your fuel receipt then input when you get back home.

Simples

I went on a run to Hereford on Monday from Chester, I filled my car up to the click then went there and back ( picking up something from eBay ) went straight back to the same petrol station and re filled it again to the first click. My dash read out said an average of 40.7 mpg so I sat and worked out exactly how much fuel I had used etc to my surprise it worked out at 39.7 mpg. So I would say that's pretty accurate :-)

But again, only if your speedo is accurate. Whilst I don't believe many people will have the extent of unaccuracy that my POS displays, most people aren't actually doing as many miles as they think they are. And therefore aren't getting the economy that they think they are.

Speedhealers are great for sorting this on digital displays on bikes, and especially useful when you've changed the gearing . Shame analog clocks on cars can't be sorted as easily (or at least, as far as I know).

Don't forget the return you get is all dependant on how regularly your car has been serviced and the condition of the engine/tyres/bearings/tracking etc. Those figures that your trip computer works on is based on a brand new car, in pristine condition, and doesn't make any allowances for anything but.

It is surprisingly accurate for me. My old car, a Civic 2.0 Type S, declared that it was getting around 37/38mpg from a tank. When worked out, it was actually closer to 33/34... which took the **** slightly, as you had to drive it like it belonged to a vicar to get that kind of mileage. Typically, it would get 35/36 on the trip computer, which was actually around 31/32. Either way, bloody irritating.

The Octavia is remarkably accurate compared to many, it does genuinely seem to work it out properly. On long drives, it used barely anything. Commuting, it uses a lot more :( still a lot less than my Civic did though!

Mine is optimistic with 0.4-0.6L/100km