One pitfall of failing to get the CO2 and MPG numbers correct is the unpleasant surprise for a buyer whose new car delivers worse efficiency than expected.
“This will cause all sorts of problems for private buyers, but especially corporate fleets, who are giving undertakings to clients and investors about corporate responsibilities for reducing their carbon footprint,” said Pejis.
This is a real possibility because of changes in engineering or spec between an order and delivery – a lead time that can extend to more than three months for a car built to order. A small spec or minor engineering change – such as a different battery or tyre brand or a component redesign – could change the actual CO2 and MPG figures in this time.
Car buyers have also become accustomed to lastminute spec changes up to the ‘build date’, but this may no longer be possible once WLTP is mandated after 1 January.
“Imagine if you specified a car on a dealer configurator with a CO2 of, say, 99g/km to comply with a significant tax threshold but, because of a manufacturing specification change, the car is actually delivered with 102g/km, raising your motoring costs,” said Pejis.
Consumer lawyers might well find a rich hunting ground if large numbers of buyers receive vehicles that diverge from the promised CO2/MPG specification. The industry could also end up with large numbers of cars rejected for a simple CO2 calculation error of 1g/km or 2g/km.
The effect of options on friction and weight, and hence efficiency figures, has already emerged, with WLTP-based price lists and brochures in use now in dealers in the UK and mainland Europe but not mandated until next January.
For example, jumping from 19in to 20in wheels can add 5g/km to the CO2 figure. But, counterintuitively, another jump to 21in wheels can add only a further 1g/km, possibly because a low-rolling-resistance tyre is specified. “There’s no trend or easy rule of thumb in this,” said Pejis.
Options known to add 2g/km of CO2 are towbars and panoramic roofs. Even a sunroof adds 1g/km.
The car maker source we spoke to also made the point that price lists are already being pruned, with high-CO2 options not being made available to European buyers if it’s deemed that “very few buyers will choose them”.