Is it credible that the new Mercedes-Benz CKS 350 petrol returns 40mpg?

I was surprised by the fuel consumption claim of 40mpg combined for the new Mercedes-Benz CLS 350 petrol model. I think the old model 320CDI was 36mpg combined (37.2mpg on 245 rear tyres). I have a 5-year-old 350 petrol, which had a combined claim of 29mpg that is only achievable on long motorway runs. I am aware that much work has been done to improve the economy of petrol engines but is this credible?

Asked on 5 March 2011 by PJ, Wendover

Answered by Honest John
No. All it means is that they stuck it on a chassis dynamometer that replicated the EC driving cycle and managed to achieve the equivalent of 40mpg in the EC combined cycle. Whether a real person can really achieve that in real life is another matter entirely. That said, over 692.3 miles in a Jaguar XJL 3.0V6 diesel I recently averaged 41mpg at an average speed of 58mph, and that is better than the official combined figure of 39.2mpg. For a better idea of the true fuel economy of recent cars, consult and participate in the Real Life Fuel Economy Register at: www.honestjohn.co.uk/realmpg
Similar questions
I recently bought a secondhand 2009 Insignia 2.0 CDTI SE to replace my 2001 Toyota Avensis 1.8 VVTI. I hoped to improve fuel economy with my change in car. The Insignia, which is a diesel, has only just...
I am looking to purchase a 3-4 year old car. What is the best petrol vehicle that provides 55 miles to the gallon?
I want to upgrade my 2006 Toyota Corrolla. I have £10,000 to spend and require a reliable, stylish and economical car that will accommodate my wife and daughter. My daily commute is 30 miles and I also...
Related models
A characterful alternative to the go-to German luxury saloons and far more engaging to drive. Diesel offers low emissions and tax but is very strong. Excellent overall refinement.
Big CO2 reductions. Four-cylinder CLS 250 CDI available at last. Precisely-built interior. Retains unique style of original CLS. Comes with full LED headlights.
 

Value my car

Save £75 on Warranty using code HJ75

with MotorEasy

Get a warranty quote

Save 12% on GAP Insurance

Use HJ21 to save on an ALA policy

See offer