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FAQs

What is MPG?

MPG stands for miles per gallon and, as this name suggests, it’s the number of miles that a car can cover on a gallon of fuel. However, the actual figure will vary dramatically depending on traffic and weather conditions, and how smoothly or aggressively the car is being driven.

How do you calculate MPG?

What Car?’s True MPG fuel tests are conducted on a rolling road, under strictly controlled laboratory conditions. This means our tests are repeatable, because outside variables such as weather and traffic don't affect the results. Tests are carried out at Millbrook Proving Ground, a centre used for regulatory approved vehicle emissions testing. Millbrook has the latest equipment for testing vehicles in a highly scientific manner.

How accurate are official MPG figures?

Like What Car?'s True MPG tests, the official tests are conducted on a rolling road, under laboratory conditions. However, these official tests don't require the engine to be worked as hard, so the resulting figures often don't reflect what you're likely to be able to achieve in the real world.

What’s the difference between MPG and True MPG?

What Car?'s True MPG figures show what you can typically expect from a car when it's driven sensibly and within speed limits, but without resorting to unusual fuel-saving measures or any 'hypermiling' techniques. True MPG results are 4% lower on average than the latest WLTP official figures and 24% lower than the old NEDC figures which were used up until 1 September 2018.

What is a ‘good’ number of miles per gallon?

The most efficient cars on sale today average almost 60mpg in What Car?’s True MPG test, but anything over 50mpg is impressive.

What effect do turbos have on MPG?

All engines burn fuel and air, but when you accelerate in a car with a turbo, this compresses the air first, increasing the amount of oxygen available to mix with the fuel, and giving the engine more power than it would otherwise have. In official tests, small, turbocharged engines also return higher MPG figures than bigger, naturally aspirated engines with similar power. However, this is because the engine isn’t being worked very hard, and therefore the turbo isn’t having to cut in; in real-world conditions and What Car?’s True MPG test, the MPG advantage tends to disappear.

How can I improve my fuel economy?

An engine burns less fuel at low revs, so changing up to a higher gear earlier and avoiding hard acceleration will improve your fuel economy. Simple steps such as closing your car's windows and clearing out the boot to reduce weight will also help. For more fuel saving tips, click here.

What is WLTP?

All new cars registered from 1 September 2018 are being tested under a new Worldwide Light Vehicle Test Procedure (WLTP), which is designed to better reflect real-world driving conditions than the old New European Driving Cycle (NEDC) test. To find out more about WLTP, click here.

What is RDE?

The official WLTP laboratory test is supplemented by Real Driving Emissions (RDE) testing which, as its name suggests, takes place on public roads. However, because RDE figures are less repeatable, they're currently only being used to verify certain pollutants, such as NOx. Diesel cars that have been verified aren't subject to the 4% benefit-in-kind (BIK) tax surcharge that other diesels are.

How do I convert l/100km to MPG?

To convert the l/100km figure that’s used in Continental Europe into MPG, you simply divide it by 282.5.

L/100km to U.K. mpg Conversion Table

L/100 kmUK mpg
1282.48
1.5188.32
2141.24
2.5112.99
394.16
3.191.12
3.288.28
3.385.6
3.483.08
3.580.71
3.678.47
3.776.35
3.874.34
3.972.43
470.62
4.168.9
4.267.26
4.365.69
4.464.2
4.562.77
4.661.41
4.760.1
4.858.85
L/100 kmUK mpg
4.957.65
556.5
5.155.39
5.254.32
5.353.3
5.452.31
5.551.36
5.650.44
5.749.56
5.848.7
5.947.88
647.08
6.146.31
6.245.56
6.344.84
6.444.14
6.543.46
6.642.8
6.742.16
6.841.54
6.940.94
740.35
7.139.79
L/100 kmUK mpg
7.239.23
7.338.7
7.438.17
7.537.66
7.637.17
7.736.69
7.836.22
7.935.76
835.31
8.134.87
8.234.45
8.334.03
8.433.63
8.533.23
8.632.85
8.732.47
8.832.1
8.931.74
931.39
9.131.04
9.230.7
9.330.37
9.430.05
L/100 kmUK mpg
9.529.73
9.629.43
9.729.12
9.828.82
9.928.53
1028.25
1125.68
1223.54
1321.73
1420.18
1518.83
1617.66
1716.62
1815.69
1914.87
2014.12
2113.45
2212.84
2312.28
2411.77
2511.3
2610.86
2710.46
L/100 kmUK mpg
2810.09
299.74
309.42
319.11
328.83
338.56
348.31
358.07
367.85
377.63
387.43
397.24
407.06
416.89
426.73
436.57
446.42
456.28
466.14
476.01
485.89
495.76
505.65