maybe a daft question!!

[bower]

just wondering if the mpg on the trip computer reads the amount of fuel the car is actually using or is it just based on revs/ speed?
the reason i ask is i seem to be using a lot more fuel recently than normal (and oil) but the trip computer reading doesnt seem to bad

[th3_f15t]

Pretty sure the instant read out is based heavily on revs and speed, but the average journey reading may be more based upon fuel used. I wouldn't rely on it giving accurate reading though.

If you're car is using more oil than usual then be very concerned, check the coolant for signs of oil or sludge, could indicate a leaking head gasket (I think).

[bacillus]

There are 2 mpg values in the cluster.
 The value with a 1 at the top right is the current trip mpg whilst the reading with 2 at the top right is the overall mpg. I suspect it's the 2 reading you're looking at as that value isn't reflecting your poor mpg.

[bower]

cheers but defiantly looking at trip 1
and ive checked coolant etc and no signs of any leaks

god knows then

[kmackgttdi]

Hi few things I'd say to check
How much oil per 1000 miles is it using?
When was it last serviced?
Plugs gapped right/not worn out? Assuming its a petrol...
Recirc valve in good nick?
The mpg reading on my gttdi 4mo seems to be fairly accurate on the average mpg, a full tank calculated out works out to within a couple of mpg if not bang on.

[bower]

thanks for the reply
to be honest i havnt been monitoring it, goin to start now. it was only when i realised i had no top up oil left and thought s**t im sure i had 2-3 litres in there only last month.
it had a full service 3 months ago by me and i replaced everything eg plugs, fuel filter. im unsure what gap theyve got i just bought bosh ones from eurocarparts which came up as for my car.
whats the recirc valve?
i know ive got a misfire on cylinder 1 which i still havnt found out what causing it, but pretty sure its either carbon build up or dodgy injector as i swaped coil packs around and it still stayed on 1 so dont know if that would cause more fuel use?
cheers

[audiman]

i know ive got a misfire on cylinder 1 which i still havnt found out what causing it, but pretty sure its either carbon build up or dodgy injector as i swaped coil packs around and it still stayed on 1 so dont know if that would cause more fuel use?
cheers

That paragraph sums it all up!

Sorry to be rude but the title of this thread seems about right. It is a daft question asking why your mpg is bad when you are driving around with a misfire!!! There are so many things that could cause this along with oil consumption. Last car I saw with your symptoms was a revo tuned car being driven on 95 fuel. It had a melted piston. Hence misfire and oil consumption.
However it could be an injector. Take it to a pro and get it diagnosed

[bower]

yeah i said it was 

but my original question was does the on board computer actually take into consideration the "actual" fuel use, because if it does then i would be quite happy with my mpg taking into account ive got a misfire, if not then i need to get the misfire sorted asap. so maybe not so daft?

[rich83]

You need to get the miss fire sorted ASAP regardless.

[bower]

 i know im just waiting till my up coming holiday to do the dreaded intake manifold removal! im not looking forward to it.

[audiman]

The display of avg mpg is a calculated value based on many factors. It is accurate to within 5%.
Manifold off isnt that bad a job, worst bit is the stay bracket underneath

[bower]

The display of avg mpg is a calculated value based on many factors. It is accurate to within 5%.
Manifold off isnt that bad a job, worst bit is the stay bracket underneath

hope so i just need to get some sort of tools and cleaning materials to clean the valves.
also does anyone know if the teflon strip on the injectors actually needs replacing if they come out with the manifold?