Book quotes 58mpg, I get about 45mpg

[Morph]

I have a 2 year old 10000 mile 2.0 ltr VRS PD TDI Estate.

Yesterday I reset the computer when driving for 30 miles at 60mph on a mainly flat dual carrigeway, I had the cruise control on and nothing else except the radio and no weight in the car and I averaged 45mpg. The book states that on non urban roads you should get 58mpg but i had to drive at 47mph to get this.

What do you guys think, is this acceptable ? :confused:

Edited 11 September, 2009 by Morph

[Chrispy]

Are you using the brimming method or the computer to get these figures? Things like tyre pressure, tyre type, head winds, air temp/ pressure, the cleanliness of your air filter, the cetane rating of the fuel (it varies) etc et - all affect mpg.

I try not to trust the computer too much as they are inaccurate so use the trip computer and work it out from miles driven and litres used. My Fabia only tends to get around 45mpg on average working out the above way when the computer reckons I'm getting about 50.

The book figures are usually very optimistic too. I found that to get into the mid 50's in the Fabia (on the computer) I needed to do about 50mph for quite a while. I found this by being stuck behind a bloody caravan for many miles on a road with no suitable overtaking spots.

[Morph]

The computer. It was a nice day yesterday, good temps not much wind, my tyres are good, have good tread and pressure and I have a K&N filter. I will try it the way you say and see if this gets me better results. Thanks

[Chrispy]

No probs - was just a few thoughts.

I used this last time to work out my mpg: http://www.torquecars.com/tools/uk-mpg-calculator.php

Overall I found I had to do lower speeds than I thought to get good mpg. Anything above 60mph and it starts to go south I find, but then the Fabia is shaped like a breeze block.

[mlapicki]

I've got a 3 yr old VRS TDI Estate (40k miles), I'm getting 47mpg doing 90% motorway driving. I find the computer is a glass half empty kinda thing, and it routinely reports 42mpg. I ignore it and calculate the litres put into the tank / miles driven. I'm also wondering whether this is bad / normal / good.

[gregoir]

Well I got 37mpg indicated today for a gentle 40 mile A road return trip BUT with two push bikes hanging off the tow hitch.That'll teach me to crow about the 50mpg for my motorway cruise the other day.Full to full manual calculation is the only way to be sure of your mpg.

[modra_vrs]

Perhaps see how you get on with the ECON button engaged. It turns the climate control compressor off. I get a 10 percent improvement on my PD 170 VRS with ECON engaged. My average over 2000 miles is 39.0 dead, but then I do mainly short journeys. The best I have got is on a motorways between 60-80 mph over 120 miles and that was 46.7mpg. I have also worked out from doing a fuel in divided miles travelled calculation , that the OBC is very accurate. In fact it was dead on, much to my surprise.

[Chrispy]

Interesting. The older ones (like the MKI Fabia) always read it several mpg too high. I wonder if they've tried to make it more realistic.

On the ECON front though, agreed - use that to disable the air con and for it to just use normal air to ventilate the cabin. Should save a bit of juice if you're not already doing this.

[sms]

check your tyre pressures to ensure tyres correctly inflated. Try the drive again using a light foot and no cruise control, you can get better mpg without cruise control and also have a search for SAFED driving, some good tips there.

[Nathanio]

Welcome to the world of massively incorrect and misleading government figures. I could match my Toledo but meant driving like a complete saint and with a very light foot!

The Prius is the worse for this with a different of about 27% in a recent AE fuel test!

To get 45mpg from a big lump like the PD170 with wide and large tyres is damn good going. Be happy with it and wait for it to increase with age. My 110 went from around 43-44MPG at 49k to a proper repeatable 50MPG at 80k

[Octygone]

Tyre pressures need to be something like 37psi front and back make sure you turn off the mirror heating and also turn off air con completely also drive on a really level road (no hills) don't use the cruise control and you have to be very light and that should just about do it but in the real world you just won't get those figures

[Morph]

I'am happy with the rate i'm getting but just felt the book or computer needed questioning because one was not right. I appreciate all the factors involved like tyres, Aircon, Weight etc etc.

Nice to see that everyone's in the same boat so I can stop worrying but would also like the book and computer to be a bit more realistic.

Will try the brimming method and no cruise and see how this ends up, ( just to see what I can get).

Thanks for your replys.

[Nick P]

Just use spritmonitor

[estelle]

I have found that when on motorways, travelling at 80ish, I can only manage about 46mpg. No matter how light footed I am, maintaining that speed constantly uses that much fuel.

I have wondered if, at those revs, I'm using a fair bit of boost & therefore reduced mpg is inevitable.

However, when I'm on A roads the economy rises significantly, so far to 50mpg. I'm still driving quickly, but because I'm on & of the throttle I can drive much more economically.

It seems backwards tbh & every other car I've has reacted the other way round, but I notice it's possible to build speed quickly, using the huge torque, & then cruise using very little throttle, MFD showing current consumption in the 70, 80's, obviously helping the average.

Incidently my MFD is usually 2mpg pessimistic, showing 48mpg while my calcs prove 50mpg.

[sms]

try and keep the revs at around 2.5k rpm