The MPG myth

The MPG Myth


A big consideration for a lot of people when purchasing or leasing a new car is the expected MPG (miles per gallon) they would achieve on motorways or with city driving. The issue is, when we start driving, we notice that the displayed MPG is no-where close to the number that the manufacturer’s estimate… Why is this? 

This is due to the way that the expected MPG has been tested, previously (Before 2017) manufacturers used a standard called NEDC (New European Driving Cycle) which was introduced way back in the 1980s with the last update coming in 1997. Now there are a few issues with a 20-year-old testing procedure, but the issue isn’t as much with the age (Although this still plays a part) but with the testing procedure itself. 

The NEDC was based on theoretical driving, with no road wear or any other road conditions considered. However, that isn’t the biggest issue, the biggest issue is the phrase ‘theoretical driving’ this unrealistic expectation of drivers. To show you how absurd some of these tests are, I’ll list off a few examples of this theoretical driving that manufactures expected in 1997: 

  • 0 – 15 km/h in 4 seconds (that’s just under 10mph) 
  • 0 – 32 km/h in 12 seconds (that’s how long it takes to get to 60 in a modern hatch, to reach 20mph) 
  • 0 – 50 km/h in 26 seconds (positively crawling and being overtaken by women with a pram on your way) 

Now, I know some slow drivers, but this makes them look more hare than tortoise. If you were to drive as the test expects you to, you’d certainly get angry looks and probably a large headache from the amount of horns you’d hear. 

However not only was the test flawed, to begin with, a lot has also changed in the automotive industry in the last 20+ years, cars have become heavier due to all the added technology but oddly the components have got lighter there is just lost more of them. Cars have become more technically advanced and got faster. For example, in 1997 the fastest production car was held by the McLaren F1 with a top speed of 221mph, now the fastest production car is a 2017 Koenigsegg Agera RS with speeds of 277.87mph. The 1.4 petrol Ford Escort of 1997 had a top speed of 105mph, and the 2019 Focus 1.0 will go 123mph. 

Another factor that has brought more stringent testing in, is that manufacturers use these results to promote their car, so they decided it was worth cheating the system rather than making more efficient cars, and the rules on testing had to stop this happening again. 

That brings us onto the testing procedure in place from 2017 until present, the WLTP (Worldwide Harmonised Light Vehicles Test Procedure). This new set of tests focuses on more realistic driving methods, these tests are based on real driving data to help give more accuracy. A few of these changes include a higher average speed (now 28.9 mph), a higher maximum speed (81.3 mph) and now the test has a longer cycle spanning 14.4 miles rather than NEDC’s 6.8 miles. As well as a whole heap more including: 

  • More realistic driving behaviour, 
  • Shorter stops in between tests, 
  • More dynamic acceleration and deceleration tests, 
  • More realistic temperatures closer to Europe’s average 


These new WLTP tests don’t just affect the way MPG is measured but also the way CO2 emissions are tested. While the emissions of a car may not be the first thing someone looks for (If it is you should look at electric vehicles such as a BMW i3), it would be an eventual check as it would dictate the amount of road tax you would need to pay for your car. 

Now with the stricter WLTP regulations will we all have to pay more on car tax? No, at least not at first glance, while you can expect CO2 emissions to increase by an average of 15%, at least in the UK we still use the previous NEDC CO2 emission numbers to work out the car tax. 

Although these new WLTP tests were introduced in 2017, manufacturers are still legally allowed to show their NEDC test results for all cars that were tested under NEDC until September 2019. 


So what does this actually mean for drivers like myself and you? Well for one the MPG stated by the manufacturers will be more accurate, so you can expect to receive the same results. So great, that means I buy a car and I will receive the manufacturers estimated MPG? Not quite, while the new WLTP tests have certainly made these tests a lot more relatable, they are still only tests, in perfect constant conditions, in a lab/ on pre-determined routes. Unfortunately, in everyday life, we can’t be that planned so expect minor difference but it’s certainly a better average than the previous testing methods.    

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