Quoted mpg figure v's actual mpg

clockworks_2

Altarf wrote: »

You also need to take account of the fact that the test doesn't really represent reality, and is only meant to be a way to compare one car against another -

The Urban test - A "cold" start, where the car is 25c (perhaps cold for a morning in California, but a bloody good summers day in the UK), "driven" on a rolling road for 2.5 miles with everything turned off (no aircon, lights, etc). A maximum speed of 31mph, but the car only averages 12mph over the 2.5 miles. So not exactly zipping along.

The Extra-Urban test - It immediately follows on from the urban test, so the engine is nice and warm, and covers 4.3 miles on the rolling road. A maximum speed of 75mph, but the car only averages 39mph over the 2.5 miles. So again not exactly zipping along, especially when you realise that they only hit 75mph for a few seconds, and they are allowed (and always take) 50 seconds to get from 0 to 60!

The combined figure is just an average of the two tests (weighted for distance).

So if you are the sort of driver who does -

a) Short journey from a 'real' cold start and doesn't drive like a nun on their way to a funeral, then you will get much worse fuel consumption than the tests;

b) But if you do long journeys with mile upon mile of light-throttle motorway cruising, then you will probably get as good as, or better than the tests.

The trouble is a lot of small diesels with high MPG figures are being sold to type a drivers, who then wonder why they don't get the high mpg figures.

I am an A driver as you have described in your post and in my Mercedes c180 kompressor I am lucky to get 26 mpg on my short journeys which typically consist of 4 miles, 15 minutes drives from a cold start.

However on the motorway i have got over 42mpg.

TighterThanTwoCoatsOfPain

BMW 118d Claimed 62mpg combined... actual 48mpg (although that is a reasonably hefty right foot and short round town stop / start..)

Broadwood

2005 VW Polo GT TDI 130 (150 with remapped ECU and K&N air-filter).

Today did 204 miles trip round mid Wales all on A roads and averaged 60.1 mpg as measured by the on-board trip computer.

The secrets are:-
1) only just enough throttle to keep up with traffic.
2) keep below 2000 rpm (turbo-diesel) but don't labour engine.
3) always read the road ahead and back off early instead of using brakes
4) on twisty roads keep speeds down to avoid constant throttle/brake/throttle/brake
5) check tyre pressures weekly
6) change oil when recommended
7) change air filter before it gets too clogged
8) don't carry unnecessary weight or luggage or roof-rack
9) leave a good gap to vehicle in front (enabling less use of brakes)

On a typical 13 mile trip to work or back on a mix of A B and C roads I usually get between 45 and 50 mpg depending on the weather and traffic. I could easily improve this to about 55 mpg just by leaving slightly more time for the journey and hence being in less of a rush.

Thus proving that for any given vehicle, good or bad fuel economy is mainly down to your driving style and weight of your right foot. Plus it depends how much you like giving fuel tax and VAT to the Chancellor.

MORPH3US

People should state if they are quoting the manufacturers urban, extra urban or combined figures.

My car is supposedly 85mpg (extra urban or 81 urban) but no trip computer so will have to work it out manually and post back at the end of the week if I remember.

Broadwood

MORPH3US wrote: »

People should state if they are quoting the manufacturers urban, extra urban or combined figures.

My car is supposedly 85mpg (extra urban or 81 urban) but no trip computer so will have to work it out manually and post back at the end of the week if I remember.

I'm guessing maybe this is a Toyota Prius? Lucky you.

MORPH3US

Not quite broadwood... Smart ForTwo CDi

jadorevintage

I do 60 miles a day. A roads, country roads and some town driving. Since I cut the town part out as much as I can, my MPG has gone up from 35 to 37.5. My car's MPG is meant to be around 37.8 I think...so not too bad!

cyclonebri1

sebdangerfield wrote: »

Thats not even been near a track yet. Not racing this one after my skills ran out in the M12!

If the last one's anything to go by though, two 20 min races would see a full tank gone!

I know where you are coming from, I've run 2 westfields and a cc cyclone as track cars, couldn't carry enough fuel to the track to see 1/2 doz sessions out. 30mpg on the road becomes about 6-8 on track :rotfl::rotfl:

I also found the limit of my driving skills, several times

custardy

MORPH3US wrote: »

People should state if they are quoting the manufacturers urban, extra urban or combined figures.

My car is supposedly 85mpg (extra urban or 81 urban) but no trip computer so will have to work it out manually and post back at the end of the week if I remember.

well i was going to say this
are they working out true MPG by what fuel they put in or using the trip computer?
also a boot full of crap will soon affect MPG,servicing,type of run etc
so this is fine for a ballpark idea but may not reflect the MPG another driver would get

DKLS

Twin Turbo Forester - claimed mpg of 28, actual 12-28mpg depending on how many turbos are spinning.