Driver tools

Britain drives in mixed units — miles on the road, litres at the pump, mpg in conversation and bar on the forecourt airline. These convert between them, exactly.

• Fuel cost

  What a mile actually costs, from the pump price and your mpg.

• Fuel economy

  mpg against the L/100km a brochure or a dashboard quotes.

• Distance

  Miles and kilometres, for imports and for driving abroad.

• Tyre pressure

  The door placard says psi and the forecourt airline says bar.

• Power

  bhp, kW and PS — which are not the same horsepower.