Cars powered by synthetic fuel emit as much poisonous nitrogen oxides (NOx) as fossil fuel engines, new emissions tests have revealed.

The T&E tests revealed that a car running on e-petrol emits equally high levels of toxic NOx as standard E10 EU petrol and much more carbon monoxide and ammonia

While several carmakers are pinning their hope on synthetic e-fuels to extend the life of internal combustion engines, and help ensure sustainable motor racing, green group Transport & Environment (T&E) said its new tests confirm that using e-fuels in cars will do little to alleviate the air quality problems in our cities.

Run by research organisation IFP Energies Nouvelles for T&E, the tests revealed that a car running on e-petrol emits equally high levels of toxic NOx as standard E10 EU petrol and much more carbon monoxide and ammonia.

And while particle emissions are considerably reduced in the switch, more than two billion particles are still emitted for every kilometre driven in an e-petrol powered vehicle.

The laboratory tests compared emissions from a car using petrol and three different blends of e-petrol – created by IFP Energies Nouvelles specifically for the test as there is currently no synthetic petrol for commercial sale.

When burned, synthetic petrol causes almost three times more carbon monoxide – which deprives the heart and brain of oxygen – compared to petrol. The e-petrol powered car also emitted up to two times more ammonia, which can combine with other compounds in the air to form particles (PM2.5) for which there is no safe level of pollution. The health risks of PM2.5 include asthma, heart disease and cancer.

T&E said that the research showed why EU lawmakers should not bow to pressure from carmakers and the oil industry to include credits for advanced and synthetic fuels into the EU car CO2 standards. MEPs and governments are currently deciding on an EU Commission proposal that all new cars sold in 2035 be 100% zero-emissions.

Julia Poliscanova, senior director for vehicles and e-mobility at T&E, said: “No amount of spin can overcome the science of burning hydrocarbons. As long as fuel is combusted in engines, toxic air will persist in our cities. Lawmakers who leave loopholes for e-fuels in emissions targets are condemning the public to decades more of avoidable air pollution.”

The eco campaign group also said that such industry proposals to allow loopholes for e-fuels in EU car CO2 targets would drive up costs for drivers.

Separate research held by T&E earlier this year found that running a car on e-fuels over five years will cost a driver €10,000 (£8,544) more than running a battery electric car. High e-fuel costs will also make running second-hand cars on e-petrol around €10,000 more expensive over the same timeframe.

Commercial production of e-fuels is also far less efficient than powering electric vehicles. Supplying just 10% of new cars with e-fuels instead of electrifying them will require 23% more renewable electricity generation in Europe, another independent study for T&E shows.

Instead, it’s calling for synthetic fuels to be prioritised for planes, most of which cannot use batteries to decarbonise and which today burn fossil fuels that may be even worse for air pollution.

Julia Poliscanova said: “E-fuels have lost the race to clean up cars, but in truth it was never even close. Battery electric cars offer drivers the cleanest, most efficient and affordable way to decarbonise, while synthetic fuels are best suited to planes where electrification is not an option. The credibility of Europe’s clean car policy is on the line and any diversion into e-fuels is a new lease of life for old polluting engines.”

To access the new T&E research on e-fuels, click here.