¿Cuál es la diferencia entre los aceites de motor para diésel y gasolina?

When you're looking for the best oil for your car, there's no single answer. One of the main reasons is the difference between the physical and chemical needs of diesel and gasoline engines. So, while there are lubricants that work for both, there are others that only work for one of them.

Keep reading this practical guide for a clear and rules-based explanation of how oils for diesel and gasoline engines differ and how to select the right one for your vehicle.

Oils for diesel and gasoline engine serve the same purpose: to lubricate, protect, and clean. But the specific needs they address aren't the same. The key lies in respecting their specifications (API/ACEA/ILSAC and manufacturer approvals) and the indicated viscosity. This will ensure optimal performance, low emissions, and a long engine life — whether it runs on diesel or gasoline.

Difference between oil for diesel and oil for gasoline

Diesel engines emit more soot, acids, and solid particles than gasoline engines. Therefore, diesel oils usually contain a higher concentration of detergent and dispersant additives, thus avoiding the formation of sludge that can generate obstructions in the operation of the different ducts.

It's a game-changer when it comes to gasoline, where the recent priority is to prevent low-speed pre-ignition (LSPI). In addition, it highlights the role of friction modifiers in improving performance and consumption.

Standards and labels for diesel and gasoline oils

Labels are the best guide for identifying which type of oil you're dealing with:

• API: In this US standard, the letter S identifies oils for gasoline engines (SN, SP) while the letter C is for diesel engines (for example, CK‑4). In some cases, you'll see combinations of both letters, which means they'll work for both.
• ACEA: On European labels, you can find A/B (gasoline and light diesel, without exhaust aftertreatment systems),[NJ1]  C (low-ash lubricants for vehicles with emissions processing, both diesel and gasoline), and E (heavy diesel).

Can I use a "gasoline" oil in a diesel engine, or the other way around?

It's perfectly normal that you've asked yourself this question. The answer is that you can only use an oil if it meets the exact specification required by your engine's manufacturer. For example, many passenger car quality lubricants carry both gasoline and diesel approvals (ACEA A/B or C, and OEM-approved).

How to choose the right oil, step-by-step

To choose the right lubricant for your vehicle, the first thing you need to do is check the manufacturer's manual. There, you will see the standards it meets (API/ACEA/ILSAC), the recommended viscosity, and, if applicable, what the manufacturer approves.

From there, consider the actual use and the climate in which you are going to use it. For example, where permitted by the manufacturer, low viscosities (0W‑ 20/5W‑30) are recommended for short journeys and cold temperatures, while options such as 5W‑40 or 10W‑30 oils are more suitable for hot climates and longer journeys.

Of course, it's always crucial to change the oil within the stipulated time frames: stretching the oil beyond the recommended service compromises protection, whether it's diesel or gasoline.

Finally, remember that you can always use the Repsol Lubricants search engine: simply type in your license plate or vehicle model to discover which products are the right ones for your vehicle.