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Also the car is not very good on mpg around 45 to the gallon and is should be 50+.
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As previously stated, the engine fault codes would be very useful. This is the first thing you should look at.
Regarding the MPG, if you could answer these questions then we'll have a better idea of what would be expected:
* How long is your average journey (miles)
* Is it stop/start in heavy traffic, or is it steady driving on A roads / motorways?
* What's your typical top cruising speed on the motorway (if you do motorway journeys).
And a few other random questions which might be useful:
Does your temperature gauge reach 90c reasonably soon? (within 5 miles)
Is there any RPM range when the engine is particularly bad?
Is there any RPM range when it feels normal (for example, 1000-1800)?
Does it feel like your accelerator has no effect after 1/3 of the movement?
How many miles has the vehicle done?
Has it had a cambelt change recently? (or any other major work in the engine compartment)
Tyre pressures OK?
Hubs not excessively hot after a long drive?