🚗 Diesel or petrol: from how many km does each one pay off

🌡️ The cliché you're being sold wrong

A lot of people assume a diesel costs more to maintain than a petrol car. In scheduled servicing, that's not the case. Norauto charges exactly the same to service a diesel as a petrol car: 84 € on cars from 2002 to 2006, and 100 € on those registered from 2007 onwards. Repsol gives the same oil-change interval for both engines, between 15,000 and 20,000 km; what changes is the type of oil, not how often you change it.

Petrol engines also have a turbo — a part costing 120 to 500 €, with 3 or 4 hours of labour, the same as on a diesel — and they also have an EGR valve, which costs the same or less to clean. The Ayvens Car Cost Index 2026, carried out in 30 countries, says that in Spain diesel comes out somewhat cheaper than petrol in total cost of ownership over 4 years and 30,000 km a year, on a compact car.

🛣️ Why diesel needs motorway driving and petrol doesn't

The particulate filter (DPF) traps soot from the exhaust and cleans itself by burning it off, but only when the engine reaches a high temperature and holds it for a while — something that happens on motorway driving, not pottering around town. The EGR valve and the AdBlue system work on the same logic: they need the engine hot and sustained.

💰 The real risk in euros if something fails

This is what really decides the purchase, more than the yearly workshop bill: what a big breakdown costs you if the filter, the AdBlue, the injectors or the turbo fail.

🔧 Where diesel really does cost more, and by how much

There is a real extra cost with diesel, and these are the four, in euros:

• Low-ash oil, mandatory with the DPF: +12 € per 5-litre jug, a +55% — 34 € for 5 litres against 21.99 € for standard oil.
• Diesel fuel filter, every 40,000-60,000 km: between 35 € and 65 € with labour.
• Glow plugs, every 130,000-160,000 km: 215 € on average in Barcelona, in a range of 140 € to 280 €.
• ITV roadworthiness test in Catalonia: +4.99 € — 45.59 € against 40.60 € for petrol.

⛽ AdBlue in Vilafranca costs you almost half price

If you do end up buying a diesel, the filling station matters. At Esclatoil 24h, in Vilafranca del Penedès, AdBlue costs 0.529 €/litre, against a national average of 0.953 €/litre — almost half. In a supermarket jug or a roadside petrol station it costs between 2.5 and 8.6 times more than at that pump. With normal use of 1 litre every 1,000-1,500 km, that's between 20 € and 75 € a year, depending on how much you use the car.

⚠️ A petrol engine that doesn't get off easy either: the 1.2 PureTech

Not every petrol engine is worry-free to maintain. The 1.2 PureTech has its timing belt running inside the engine's oil bath, and that raises preventive maintenance costs: between 400 € and 800 € at an independent garage, between 800 € and 1,200 € at an official one, and "several thousand euros" if the belt actually breaks. That's why at GSM we don't buy cars with a 1.2 PureTech engine for stock: it's one more selection criterion, just like we check the DGT environmental label or the car's history before deciding whether it comes in.

🧾 If you have a Stellantis diesel with a faulty AdBlue system

Stellantis groups together Peugeot, Citroën, DS, Opel and Vauxhall. It has a programme that compensates AdBlue tank repairs on Euro 6 diesels with an SCR system manufactured between January 2014 and August 2020, up to 210,000 km and 8 years.

It pays 100% of the parts if the car is under 5 years old or 150,000 km. Between 5 and 8 years, it pays between 30% and 90%. This is reported by dsca.gob.es and the OCU, and the programme is managed at stellantis-support.com.

✅ The essentials, at a glance

• 🛣️ Diesel pays off above 15,000-20,000 km/year on the motorway, the threshold Repsol cites.
• 🌡️ Scheduled maintenance costs almost the same for both: Norauto charges 84-100 € to service either one, with the same oil interval.
• 💰 The real risk if something fails: DPF 1,200-2,800 €, AdBlue 336-1,487 €, injectors 1,200-2,200 €, turbo 1,200-2,500 €.
• ⛽ AdBlue in Vilafranca del Penedès (Esclatoil 24h) costs almost half the national average.
• 🔧 Petrol also has a turbo and EGR: it's not true that it gets off those breakdowns, they just get dirty more slowly.

❓ Frequently asked questions

From how many km a year does diesel pay off?
From 15,000-20,000 km a year, mostly on the motorway: it's the threshold Repsol cites. Below that, and mostly in the city, petrol gives more peace of mind.

Is a diesel more expensive to maintain than a petrol car?
In scheduled servicing, no: Norauto charges exactly the same to service a diesel as a petrol car, and Repsol gives the same oil-change interval for both engines.

How much does a big breakdown of the particulate filter or AdBlue cost?
The particulate filter (DPF) costs between 1,200 € and 2,800 €, up to 3,500 € on a large SUV. The AdBlue module, between 336 € and 1,487 €, based on real dealer invoices.

Does GSM buy cars with a 1.2 PureTech engine?
No: because of the cost and risk of the timing belt running inside the oil bath, at GSM we don't buy cars with a 1.2 PureTech engine for stock, just like we check the DGT environmental label or the car's history before deciding whether it comes in.