MPG - How accurate is computer??

[ifti]

On a spirited drive, you can almost see the needle moving down to the empty mark! lol

However, I just went out and was stuck mainly down the A127, which has average speed cameras at 50 and 70mph, pretty much all long it.
The entire trip had only a few minutes or so through a town, and the rest on motorway or A127 Dual carriageway.

Filled up to the brim, and then drove like a grandad because of the cameras, and to see what I could get out of the car.
Throughout the trip, mpg went high and low. However, I was shocked to see 133mpg at one point! (steady downhill) Although it only for a second!

After the entire trip (around 70 miles), I checked the average mpg as I parked up, and was suprised to see 36.8mpg!!
After the 70 miles it also still thinks I have another 375 miles until next refuel! 

How accurate is this thing? lol

I guess it all is down to how you drive!

[smartypants]

Not got my Golf yet so can't comment on your car - but in my experience driving various cars from BMW to Ford to Porsche's all trip computers are very inaccurate.

The most accurate way to measure your MPG is to fill up, reset the trip computer, do your trip and then fill up again - noting the amount of fuel and the reading on your trip computer - and then do your maths

[DJGTi]

I've checked the computer against actual fill ups a couple of times and found it to be within 0.1 mpg over a full tank. I was amazed as I've seen some that are over 10% out.

[ifti]

Yup, I reset my trip meter when I filled up. Habit I guess!
Will work out what I get once I refill again - hopefully it will get me through the week!

[stealthwolf]

Also remember to reset the average mpg after filling up.

I've found 'miles remaining' or 'range' to be dependent on your last average mpg reading, so if your average mpg was 20, your 'range' on a full tank will be lower than if your mpg was 40.

I've found the range to vary from as low as 300 miles to as high as 375 miles (and then stay at that reading for 25 miles because I've been cautious).

[Jkctr]

I had the one that reads while you drive show 99mpg 

The average is accurate, dont believe the 'while you drive' one 

[ifti]

How do you reset the average mpg reading?

[Jkctr]

It does it after you stop and does a new one for the next journey.

[ifti]

It does it after you stop and does a new one for the next journey.

Yeh I thought it had reset when I left this morning - nevertheless, was well chuffed to see I could get above 35mpg out of it when Im really strapped for cash!! Need to wait for next pay day so cant put my foot down to much at the mo!
lol

[stealthwolf]

How do you reset the average mpg reading?

Use the button on the bottom of the right stalk (not the toggle button). Keep it pressed for more than a second and it'll reset. If you don't press it for long enough, it'll switch to the second average mpg reading (which I believe is the life mpg reading).