Trip Computer Mpg - How Accurate?

[Catweazle]

Well after a year of looking I have finally bagged myself a 2005, 5 Door, Petrol, XT4 in two tone Carbon Quartz over silver.

Already I have a million questions to ask but to avoid pushing my luck too far, will post them gradually. The first one however, is how accurate is the trip computer average MPG reading. I've just been out for a spin (mixed round town and fast A roads) and have got a reading of 35MPG. I'm taking that with a pinch of salt but is there a rough percentage you can knock off to get a more realistic reading?

Thanks in advance everyone

[Manxrav]

I defo would have gone for a diesel version!!!!

Regards Clare

[IanXT4]

Try taking off 15%, this works for me !!

Most useless computer fuel gauge I have ever come across.

I am sure it was designed by someone in sales department especially for the test drive.

Ian

[Catweazle]

Thanks Ian

Anyone else agree with knocking 15% off

[three5]

Thanks Ian

Anyone else agree with knocking 15% off

Hi Catweazle,

I have an XT5 with the D4-D engine. It's got just 16k miles on the clock now and over the whole of that time the OBC has registered 12.8% more than the brim-to-brim calculation. Really can't work out the logic, it's no more of less accurate on short v long runs or winter v summer. At best it is 8% out and at worst and 18%.

[local hero]

Thanks Ian

Anyone else agree with knocking 15% off

Having just, 2hrs ago got back from a week in Pemrokeshire, I did a pretty accurate fuel check, going 210mls OBC showed 49.7mpg, actual fuel used brim to brim worked out at 41 mpg, on return 202.2 mls 52.3 mpg see pic..

I have a scangauge fitted if you look at following pic bottom left fig 9.1ATD refers to 9.1 litres per mile, which again works out at about 41mpg Ive not as yet re-filled to verify brim to brim, but this shows roughly 20% discrepency, I don't suppose 41mpg is too bad as i was driving quite enthusiastically + car was fully laden but a bit dissapointing compared to OBC figures.. Stew

[bothwell_buyer]

One should remember that a 5 door is a hefty motor. Anything over 27mpg is a bonus.

And remember that your trip meter is a bit of cheaply made kit...almost as cheap as some of the latest tech wizardry being recalled all over the world. Its accuracy is not an essential part of any Health and safety regulation....enjoy the motor and keep feeding it fuel whilst fuel still exists! Number 1 RAV is off the road now due to the shortage/non-existance of the fuel it is tuned to drink - Shell vpower.

[Mike JD]

Thanks Ian

Anyone else agree with knocking 15% off

At least that! Petrol 2004 4.2 XT3: indicated 40.2mpg, actual (brim to brim) 33mpg over the test period of the last 3000 miles since mid January. One poster here said it was the worst trip computer he had come across and I second that. Great car but it does tell whopping lies.

I am surprised though at how clean it stays (relatively) despite the appalling state of the roads and lanes round yur in this never ending winter. I don't need to go off the road to go off-road.

Mike D

[Davrav]

I don't need to go off the road to go off-road.

Mike D

Problem is the road is going 'off road' around here - soon won't be much surface left, just a strip in the middle in many areas

[Zim1]

27 would be nice.. Mine doesnt seem to be too bad, trip is reading 23.4, last brim to brim worked out to 22.3...

[raverchris]

Just posting in case this info might be useful to somebody.

Glad to find that my 2007 xt4 D4D is normal in having an inaccurate fuel consumption.

Over 8000 miles of mixed driving the true average is 45.7mpg.

Computer has been anywhere between 12% and 29% wrong, generally 15% too optimistic.

I have a feeling that something isn't quite right with the calculations when in 5th & 6th gear, but nothing concrete.

I think I will stop worrying about it now.

My old 2003 D4D averaged 41mpg over the 38000 I had it. That OBC was consistent 10% over.

Lowest 32.6mpg highest 45.8mpg.

[benxt5]

My 2006 xt5 d4d is also out by 20-25%. I tend to get screen values of 56mpg on a motorway run and 46mpg on normal mixed commute. That compares to calculated figures of 43mpg motorway and 36mpg on the mixed commute.

[wharfstaff]

Filled up my 2007 D4D twice since getting it on 1 Dec and just searched for posts on trip computer because first fill was 48 mpg on trip comp and 40 mpg calculated, second fill was 44 mpg on trip and 36mpg calculated.

When I put a tuning box on my Astra 1.9 Sri cdti the trip comp went mental, I was thinking that maybe the Rav had a box fitted by the previous owner and was still on, but it looks like the inaccuracy is just a feature of the product.

[Mike JD]

Filled up my 2007 D4D twice since getting it on 1 Dec and just searched for posts on trip computer because first fill was 48 mpg on trip comp and 40 mpg calculated, second fill was 44 mpg on trip and 36mpg calculated.

When I put a tuning box on my Astra 1.9 Sri cdti the trip comp went mental, I was thinking that maybe the Rav had a box fitted by the previous owner and was still on, but it looks like the inaccuracy is just a feature of the product.

It surely is a well known feature but it is easy so remedy. Black sticky tape over the display and enjoy everthing else about the car!

[wharfstaff]

Nice one Mike! Don't mind it being inaccureate, everything is relative, so if I drove like a granny (Ooops, can't really say that, I am a grandad and sleeping with a granny) I get 50 mpg on comp 40 mpg actual. Less than 50 mpg on comp will be less than 40mpg actual, no probs.

I love the car and its been brill in the recent bad weather, although on the East Anglian coast we didn't suffer much, only minor side roads were coverd for a few days, A roads were fine.