Are manufacturer fuel consumption figures reliable?
Combined Fuel Consumption (mpg) For some time now the MPG's published by car manufacturers have been under the spotlight with 'real world driving conditions' delivering for some cars significantly less MPG than those published by manufacturers under laboratory conditions.
For some vehicles this difference can be as much as 40% , independent tests show that on average official MPGs are 20% less than those obtained under 'real world driving conditions'.
Official Car Manufacturers Fuel Consumption Figures Explained
Why the EC figures do not represent true MPG
Standard tests are carried out in laboratory conditions and as a result are not fully representative of real live driving conditions. Driving conditions can vary significantly with excessively high or low temperatures impacting fuel consumption, also an individuals driving style will also impact fuel consumption rates.
Urban Fuel Consumption (mpg)
Tests carried out from a cold start, on a rolling road with a temperature environment of between 20 - 30 degrees Celsius. Maximum speed 31mph, average speed 12mph and distance covered 2.5 miles
Extra-Urban Fuel Consumption (mpg)
This test is carried out immediately following the Urban Fuel Consumption test and consists a mixture of approximately 50% steady speed driving with the remainder a mix of accelerations , decelerations and idling. Maximum speed 75mph, average speed 39mph and distance covered 4.3 miles.
Combined Fuel Consumption (mpg)
This is a combined mpg , averaging the urban and extra-urban consumption test results weighted by the distance covered in each test.
New fuel consumption tests being introduced - Worldwide Harmonised Light Vehicle Test Procedure (WLTP)
The WLTP fuel consumption tests are being introduced to give the consumer a more accurate indication of true fuel consumption, tests will be aligned to more 'real world' driving conditions.
The WLTP will mandatory for all new cars by September 2018 and the tests whilst being representative of 'real world' driving conditions they will still be conducted in a laboratory ensuring that meaningful comparisons can be made between cars fuel efficiency