a few tips from a money saving website
While paying less for your petrol will save you money; using less petrol helps too. The obvious route is to use your car less.... do you really need to drive to the local shop? Yet even without this, you can use less fuel by driving more efficienty; it's estimated that someone who averages 35 miles per gallon (in old money) could get 40 mpg by driving better. This is a nearly 15% saving....
Always fill up the car before the indicator drops to a quarter full tank.
Thus there’s no panic and you’ve enough time to get to a cheaper petrol station. Leave it longer and you’ll fill up at ‘the next one I see’, and that usually means paying more.
Only use ‘better fuel’ if your car can cope.
Many stations sell ‘high performance fuels’ yet there’s little or no performance difference for most non-performance cars; so only fill up with the super-fuels if you've a sports-type car that you've been specifically advised will actually utilise the petrol correctly.
Keep your tires correctly inflated.
Lower tire pressure increases the drag on a car meaning you need more fuel, so check the pressures are correct regularly.
Fill up at night, but don’t overfill.
Petrol pumps are calibrated by volume, so fill up at night when it’s cold and you get a miniscule bit extra. This is also a reason not to overfill the car after the nozzle clunks, as any excess may go out of the overflow and be wasted.
The following tips are courtesy of the RAC on how to drive more fuel efficiently.
Drive smoothly in the correct gear.
Always drive in the highest gear possible without labouring the engine, plus think ahead and slow down gradually, rather than heavily braking late. This will increase fuel efficiency by up to 30%.
A lighter car uses less fuel.
De-clutter your car as extra weight means more fuel use.
Get into cruise control.
If your car offers cruise control, be sure to use it on long journeys. It'll help save fuel.
Keep your filters clean.
Dirty air filters increase fuel consumption by a significant amount, so make sure you check and change them as often as possible. They're inexpensive and quite easy to fit in most cars. Full details should be in your owner's manual.
Don’t keep the engine running unnecessarily.
Drive off as soon as you start up and switch off the engine as soon as you reach your destination. Air conditioning also uses an incredible amount of fuel so make sure it's turned off unless you really need it.
Take your roof rack off.
Take it off when it's not used to reduce the drag on the car and also don't unnecessarily open the window either as that makes driving less efficient.