4.4 V8 poor mpg on the motorway

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Waitey

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93
On a cruise at 70 it's doing 16mpg and needs a hell of a lot throttle to get it to accelerate.

It doesn't missfire though.

Im going to renew the airfilter and plugs, maybe a new maf too?

Anything else I should look into?
 
Odd thing is it does about 16mpg on normal use and is quick on kickdown. It just won't accelerate in gear on the motorway!
 
all of the above. i've gradually and incrementally changed plugs, fitted magnecor leads, changed all oils and filters, cleaned maf, adjusted stepper and replaced exhaust mid box, oh and started using better fuel too instead of supermarket pi$$. each step has improved performance and mpg a teensy bit but taken together its quite astonishing to realise how far below its ability the car was being forced to perform! nothing had actually failed but by simply ageing and no longer being optimum they were all robbing the car of performance. all those adverts that these plugs or that filter or some other lead will increase your HP are bollocks, what they do are restore power that was already there but had gotten lost. what you want to do is free the engine and drivetrain to run as it was intended to and you'll be surprised by the improvement.
 
Definate 24.9mpg - 4.0litre P38 though not the newer one in the above post. (helps if I read things first)

I was watching it like a hawk driving it home when we brought it.
Averaging 17.2 at the moment to work and back.
 
jay140285 said:
Definate 24.9mpg - 4.0litre P38 though not the newer one in the above post. (helps if I read things first)

I was watching it like a hawk driving it home when we brought it.
Averaging 17.2 at the moment to work and back.
Click to expand...


is that going by wat the car says? or are you filling a certain amount then seeing how many miles you get from it and converting over?
 
jay140285 said:
Definate 24.9mpg - 4.0litre P38 though not the newer one in the above post. (helps if I read things first)

I was watching it like a hawk driving it home when we brought it.
Averaging 17.2 at the moment to work and back.
Click to expand...

The car calculated figure is notoriously inaccurate, 27/28mpg on the display equates to 24mpg in reality on my DHSE.
The only way to check is brim to brim and re-set the trip each time.
 
That doesn't seem too bad what you are getting, I drive a 4.6 v8 and get around 18 MPG at any speed between 50-70 with my tyres pumped up above average (35 front 40 back).
 
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