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ferngreenfocus
1.6 tdci focus style fuel consumption help
hi new to the forum....so hello

i purchased a 58 plate 1.6 tdci today for economy reasons and with 24700 miles on it i am chuffed to bits with it. 30 quid road tax who could want more. i worked it out at 137.9p a litre and based on 60mpg that 9 pound should put 90 miles more on the cars range on the trip computer. it put 93 miles on it...so i was made up. but i am finding that the miles come of the cars range a bit quicker than i suspected. for example i have just done a 2 mile journey but the cars range went down by 3 miles. so do i have anything to worry about ? im new to diesel cars and think i might be right by saying economy is worse in the winter. i have a 2 month warranty. the car is in mint condition really well looked after. any advice please
ferngreenfocus
More confused and concerned that I have a fuel problem. Just done a four mile journey and the range of the car went down 9 miles. Another notch up on the menu and I am currently 37.2 mpg. Why so low..... Should be 60 mpg at least....any ideas please
rojariggs
It is always going to be inaccurate working out what £9 will do based on the trip computer. Trip computers are a guide and can vary from reality.

What you need to do is get the fuel gauge down to a specific level (eg Exactly half way, when the light comes on, etc). Then stick an amount of fuel in and drive until the gauge gets back to the same level. You will then accurately be able to calculate your MPG from the mileage you have done and the fuel you put in:

1. Convert the litres you bought to gallons by dividing by 4.54 (eg 35 litres divided by 4.54 equals 7.09 gallons)
2. Divide the miles covered by the number of gallons to get your MPG (eg 400 miles divided by 7.09 gallons equals 56MPG)

In your example of a four mile journey, at this time of year, your engine will not have warmed up. Diesels take much longer than petrols to warm up. Also, unless the four miles was all dual carriageway you must take slowing and accelerating into account. On a journey that short in the cold, around 40mpg sounds fair. Also, you drive diesels differently to petrols if you want good MPG - keep your revs low changing gear below 2500rpm. Diesels have greater pulling power (torque) at lower revs than petrol cars so don't need to be revved to make progress.

Before you start worrying about the MPG, do the above test taking several journies and types of road over several days into account. Only then will you know your true consumption.

Cheers

Rog
ferngreenfocus
thanks for your reply mate
ferngreenfocus
does this sound the norm to you rog as i see you have a 1.6 tdci too ?
TDCiST
My tank ranges from 55mpg to 42mpg on the trip meter... Mainly because of my driving style!!

I have a heavy foot, but if I do take it carefully I'll see good results.

Currently the trip is showing 47.7mpg. This is a combination of motorway at 70, and town driving.

When I did 4 longish motorway journeys on my last tank I saw 54mpg.

The tank before that was all short town journeys. I was lucky to keep the mpg above 42!!

The cold weather doesn't help, neither does traffic jams, or any stop start driving.
shanemarsh
Hi, i live above holmfirth in the pennines and i seem to drive everywere uphill, so my 1.6 tdci is averaging 36.6mpg.On a long motorway journey it creeps up to 55/60mpg and the range gets longer.
rojariggs
[quote name='ferngreenfocus' timestamp='1325892852' post='159840']
does this sound the norm to you rog as i see you have a 1.6 tdci too ?
[/quote]
It's difficult to say what's right until you test a bit more.

Also, have you reset your computer? If you've just bought it then the last few times it's been driven will have been just shunting around the dealer's yard or idling in the workshop. This will make the average MPG very low. The range is based on the last few miles driving so this will also be low.

You need to reset every one of the trip computer settings (by holding down the button when in each mode) and then do some testing working it out manually as I described above to be able to assess if you have a problem.

Cheers

Rog
Pidu
[quote name='rojariggs' timestamp='1325889833' post='159828']
What you need to do is get the fuel gauge down to a specific level (eg Exactly half way, when the light comes on, etc). Then stick an amount of fuel in and drive until the gauge gets back to the same level.
[/quote]

Such calculations will be still inaccurate. The reason is simple - fuel gauge is far away from being perfect and precise, it is also hard to get to petrol station exactly in the right time. The right way is to fill the tank up to full, reset the daily odometer and hit the road. After some miles (200-300 or more) fill the tank full again, note the amount of fuel from fuel distributor and daily odometer indication and use this values for calculations. There is no better way to measure MPG.
TDCiST
I measure mine from fill up to fill up... and by using the amount of miles i have done.
rojariggs
[quote name='Pidu' timestamp='1325961311' post='159965']
Such calculations will be still inaccurate. The reason is simple - fuel gauge is far away from being perfect and precise, it is also hard to get to petrol station exactly in the right time. The right way is to fill the tank up to full, reset the daily odometer and hit the road. After some miles (200-300 or more) fill the tank full again, note the amount of fuel from fuel distributor and daily odometer indication and use this values for calculations. There is no better way to measure MPG.
[/quote]
While I agree about the difficulty in getting to a petrol station at exactly the right time the principle is sound.

The gauge will read half with the same amount in the tank everytime - It may fluctuate a bit but will be at least as accurate as using a brimmed tank even this as your measure can e affected by different pumps and different temperatures will affect how much fuel you put in when you fill up.

I always calculate based on a full tank but was trying to give this guy a quicker and cheaper way of establishing his mpg.

Either way as to be a better bet than thowing in an arbitary amount of fuel and seeing what the range on the trip computer says!

Cheers

Rog


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