A fast guide to WLTP

Published 23 May 2018
in Advice
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What is WLTP?

A new acronym to talk about down the pub or a just a shortened version for: Worldwide Harmonised Light Vehicle Test Procedure.

WLTP is a new laboratory test used to measure fuel consumption and CO2 emissions from passenger cars, as well as their pollutant emissions.

It replaces the current NEDC test that has prevailed since the 1990s, notorious for suggesting that you’d get 60 MPG when in practice you got 35 MPG and most definitely outdated through both evolutions in driving conditions and technology.

For the more technical minded

As well as the much talked about CO2 emissions the testing of pollutant emissions  is also significant. It introduces measures of nitrogen oxides (NOX), particulates by mass and number (PM/PN) and carbon monoxide (CO). So don’t automatically assume that this means WLTP is anti-diesel.

While it will of course catch out diesels, it’s also why most new petrol cars are being quietly fitted with a particulate filter for the first time. Direct injection petrol engines emit lots of ultrafine particles and these do make a difference. If you were about to buy or lease a Ford Fiesta, you would want the one with the filter but private buyers are only just becoming aware of this.

Why does it matter?

If you are looking for a car in 2018, it probably does impact things like how long you can expect to wait, and indeed how much is on offer. What is more, if you plan to keep the car for 3-4 years or more, things like VED (road tax) are likely to jump up in cost from 2020 onwards.

The good news is that quoted MPG figures, for example, are more likely to be accurate under WLTP.

The bad news is that, without doing a thing, your existing car is about to become less efficient and more polluting, as the WLTP figures wise up to reality.

Come 2020, smaller cars are predicted to suffer a ruder awakening than large ones, an unintended outcome that the government doesn’t like.

As of May 2018, the main impact is the stock shortages we are seeing as manufacturers re-test their vehicles. It’s a very real issue with lead times for some new vehicles going out to six months.

The impact to some of our most popular manufacturers is explored below:


Porsche are closing the factory completely for an extended period of time and switching to a new exhaust system, as well as investing hundreds of millions to ready their production line for the ‘Mission E’ product line being launched in 2019. 

Jaguar Land Rover

Perhaps the most affected brand in the UK premium market, Land Rover are taking the change very seriously, discontinuing a number of models and delaying production of various cars already on order whilst the new testing is complete.

The manufacturer is switching to ‘Model Year 19’ meaning changes to price, emissions and model line ups, and very long lead times on models such as the Range Rover and Range Rover Sport.


Although less dramatic than other brands, Mercedes new vehicle orders have at times been held by up to 4 weeks before being allocated a ‘build slot’, meaning clients are likely to see inevitable delays later in the summer.

Volkswagen Audi Group

Understandably wary of any high profile issues relating to emissions, Volkswagen and Audi brands in particular are seeing increasingly long lead times (6 months for a VW Tiguan factory order for example), as well as a series of heavily discounted offers to sell off the pre-WLTP vehicles that are either in stock or already in the pipeline.


Finally, BMW are rumoured to be completely changing their model line up, perhaps more than any other brands, with the German brand’s plug-in hybrid models perhaps seeing the most change.

When is it happening?

We’re right in the middle of a transition period that began last September and continues throughout 2018. From September 01, 2018, all new cars must be measured for MPG and CO2 by WLTP.

For now, advertisements for cars still display the old figures.

Expect a ‘Big Bang’ on Jan 01, 2019, from which date cars will be marketed with the new figures.

The DfT recently claimed that the use of WLTP figures as the basis for VED would likely begin on January 01, 2020, allowing an extra year to soothe the fears of car owners and offer forward visibility around VED ‘shocks’.

Action stations?

WLTP will almost certainly affect CO2 emissions – in most cases pushing them upwards. This means Benefit In Kind (BIK) company car taxation, on which CO2 is based along with the P11D price, is likely to rise.

Companies may wish to reconsider their car acquisition methods to ameliorate the BIK rise. Instead of the company car, salary sacrifice, cash alternatives or salary increases may be the answer to defray rising BIK costs.

Is there anything else I need to know?

There is another acronym, RDE which stands for Real Driving Emissions test. It’s an ‘on the road’ test that complements WLTP. In the future benefit in kind tax bands will rest on WLTP and RDE put together.

BREXIT is unlikely to change anything because the UK won’t have ‘left’ before these changes take place, while air quality campaigners are likely to ensure that the UK stays on the virtue wagon anyway.