Used diesel or petrol: which should you choose today?

For most buyers, petrol is the simplest choice: a diesel only makes up its higher purchase price on high mileage, and its emissions-control parts are expensive when they fail. A diesel can still make sense if you do a lot of driving on main roads or motorways, with a well-maintained model and outside zones that restrict its use.

Here is the calculation, using fuel prices from 7 October 2026 and the consumption figures in our guides.

How much does a diesel save per kilometre?

Diesel costs more than petrol at the pump: €2.347 per litre against €2.14 per litre for SP95-E10 (national averages on 7 October 2026, figures from our data; prix-carburant.eu shows €2.345 per litre for diesel). The saving therefore comes only from lower consumption. For three models in our guides, using the consumption figure given in each guide:

These gaps are modest: between €74 and €245 a year for 10,000 km. The consumption figures come from different sources depending on the guide, and the diesel Qashqai is an automatic whereas the petrol version is a manual, so read the guides before comparing.

At what annual mileage does a used diesel pay off?

That depends on the premium you pay at purchase, which you will need to measure yourself from the listings. The calculation: mileage needed = extra cost ÷ saving per kilometre. For every €1,000 of extra cost of a diesel over the equivalent petrol:

• Clio V: about 78,700 km to pay back;
• Qashqai II: about 40,800 km;
• Touran II: about 135,300 km.

Divide by the number of years you plan to keep the car. With €1,000 of extra cost and 5 years of ownership, you would need to drive about 15,700 km a year in the Clio, 8,200 km in the Qashqai and 27,100 km in the Touran. With €2,000 of extra cost, these thresholds double.

This calculation only counts fuel. It ignores possible repairs to the emissions-control equipment (see below) and the cost of AdBlue. In practice, a diesel is generally worth considering from around 20,000 to 25,000 km a year for a city car or a compact, and slightly less for an SUV or a large car that uses a lot of petrol. This benchmark is a consequence of our calculation, not an official figure: redo the sums with the price in the listing you are looking at.

Which Crit'Air sticker does a diesel or a petrol car get?

According to Service-Public.fr, there are six stickers, and the number is higher the more a vehicle pollutes. For a petrol-engined car:

• Crit'Air 1: petrol Euro 5 and 6 (from 2011);
• Crit'Air 2: diesel Euro 5 and 6 (from 2011), and petrol Euro 4 (January 2006 to December 2010);
• Crit'Air 3: diesel Euro 4 (2006 to 2010), petrol from 1997 to 2005;
• Crit'Air 4: diesel from 2001 to 2005.

A recent diesel is therefore Crit'Air 2 at best, whereas a recent petrol car is Crit'Air 1. This difference matters as soon as restrictions target Crit'Air 3, or even Crit'Air 2. The sticker costs €3.85 and is ordered from the official site certificat-air.gouv.fr.