The Audi A4 35 TFSI and 40 TFSI use the same 2.0-litre turbocharged four cylinder engine, just with a different state of tune to provide 150 PS in the 35 TFSI and 204 PS in the 40 TFSI, as well as additional torque. As far as the official figures are concerned the 40 TFSI is slightly better with a claimed fuel consumption of 45.6mpg compared to 43.5mpg in the 35 TFSI, as well as fractionally lower CO2 emissions. In the real world this may not translate to a significant difference in terms of economy, the VED rate will be the same (assuming both are under the £40,000 premium) but you may find insurance costs are slightly higher for the more powerful 40 TFSI version.

The reason Audi use the same engine in two different guises is that it is cheaper to build many examples of the same engine with few or no mechanical differences while offering the customer a choice of power outputs and charging a different sticker price.