What is WLTP? New worldwide emissions and fuel consumption test explained

New European laws on fuel economy

What do new European laws on fuel economy mean for drivers? Read on to find out.

WLTP figures explained

The way cars' fuel consumption is measured changed a couple of years ago. Car manufacturers used to use a test called the NEDC (New European Driving Cycle), but the results weren't really representative of how cars performed on the road – the test hadn't changed since the 1990s. They were fine as a point of comparison for drivers choosing between different vehicles, but didn't provide an accurate estimate of the fuel economy a car was likely to achieve. This also meant governments had no reliable data on cars' carbon dioxide production, which is of course directly related to fuel consumption, and whether it met legal standards.

So in September 2017 a new test was brought in, called the WLTP (World Harmonised Light Vehicle Test Procedure). This was designed to be more reflective of real life, and allow vehicles to be compared all over the world.

How is WLTP different?

Like the NEDC, the WLTP is still a laboratory test (so that cars can be tested under clear and repeatable conditions and hence compared properly), but simulates longer distances, a wider range of driving conditions, higher speeds, sharper accelerations and decelerations, and temperatures closer to the European average. Optional equipment is also included, so for example you can see how fitting bigger alloy wheels will affect your fuel consumption.

Car tax

Because the WLTP is more rigorous, fuel economy and carbon dioxide figures both appear worse than they did under the NEDC test. As a very rough guide, if you tested the same car under both systems you would expect to see around a 20 per cent difference, but in some cases it can be up to 40 per cent. The discrepancy is generally greater in smaller cars with better fuel economy.

The Government is cutting company car tax for new cars (which increases the more carbon dioxide a car produces) for 2020-1 and 2021-2 to compensate for this, following a consultation at the start of the year. Road tax, however, will not change. The Government says it wants to “strike a balance between protecting consumers and meeting our climate change commitments”.

Real driving emissions test

The EU has also introduced another test for new cars that measures pollutants such as nitrogen oxide and soot to make sure they are also within legal limits. This is called the real driving emissions test and takes place on roads as opposed to in a lab, again in a variety of conditions. New cars which don't pass can't be sold in Europe. Cars already on the road aren't affected.

At Harlowand Maidstone car dealers Carwise Group, we have a wide range of great value, highly economical used cars for sale– and we're more than happy to answer any questions you have about any aspect of motoring. If you'd like to test drive one of them, call us on 01622 233151 or 01279 216163. Ask us about our car finance deals too.