High-performance ‘muscle cars’ have lower carbon dioxide
(CO2) emissions after going through Worldwide harmonised Light vehicles Test
Procedure (WLTP) than their New European Driving Cycle (NEDC) correlated figures,
according to an analysis by Autovista Group, which owns Glass’s Guide.
By contrast, many cars that are considered to be
environmentally-friendly, have higher figures.
The Lotus Exige Cup 430, Ford Mustang 5.0 GT automatic
and manual derivatives and the Subaru BRZ manual all had WLTP CO2 emission
figures below their NEDC-correlated equivalent, although the automatic version
of the Subaru BRZ was higher.
The UK government has said that it will introduce a motoring tax system based on WLTP CO2 values in
April 2020. Until then the current system based on NEDC data remains in place.
During the current ‘transitional period’ vehicles tested
to WLTP protocols then see the resulting figures ‘converted’ into a so-called
NEDC-correlated value using a European Commission-produced mathematical tool.
It had been anticipated by the motor industry that
NEDC-correlated figures would be tax neutral, but the reality has proved to be
somewhat different. Autovista Group has previously reported that WLTP
CO2 emissions figures were averaging 25% higher than NEDC-correlated values and
the latest data reveal that the average discrepancy between the WLTP and
NEDC-correlated figures now stands at 22%.
As Autovista Group highlights the new CO2 figures
highlight a challenge for legislators in how high-performance cars will be
taxed in light of WLTP testing. Simply adopting WLTP emissions figures would
make the tax burden on such ‘muscle cars’ lower than with NEDC-correlated
figures. By contrast, many cars considered to be environmentally-friendly would
face significant tax hikes.
Autovista Group said: “This would appear to defeat the
object of the more sophisticated WLTP test. The reality is that cars are more
polluting in the real world than under NEDC test conditions and the new WLTP
process is focusing attention on this.”
However, the cars still produce high CO2 emissions under
WLTP testing, ranging from 191g/km CO2/km for the manual BRZ to 271g/km for the
But, said Autovista Group: “It does present an
interesting challenge for policy makers who will surely not be keen to reduce
the tax burden on such vehicles.”
In its newsletter (7
June, 2018), it added: “Conversely, initial analysis reveals that many cars
with comparatively low CO2 emissions are suffering from far higher WLTP:
NEDC-correlated ratios. This is because the demands of the faster WLTP test
cycle are greater than they were under NEDC testing and less powerful engines
are having to work harder. This includes increasing the injection of fuel,
which in turn increases fuel consumption and emissions. Paradoxically, these
efficient models will all be rather heavily penalised compared to today if tax
regimes adopt WLTP emissions figures.”