SYNTHETIC OR MINERAL OIL? WHEN IS IT TRULY WORTH USING THEM AND MISTAKES TO AVOID
In the workshop, it's one of the most frequent questions: "Is synthetic or mineral better?". The short answer is that there is no universally better oil, only the one most suitable for the engine and the actual use of the car.
This guide is intended for owners of older cars, second vehicles, or cars with low annual mileage, who want to perform maintenance thoughtfully, without wasting money or risking unnecessary damage.
In this guide, you will find a technical and impartial comparison between the main engine oil manufacturers, with real pros and cons for each use.
👉 What is the best engine oil? 2026 Guide to the best brands
📋 WHAT YOU'LL FIND IN THIS GUIDE
🔍 WHAT MINERAL OR SYNTHETIC OIL REALLY MEANS
Let's leave laboratory chemistry aside. In practice:
- Mineral oil: derived directly from petroleum refining. It is less stable at high temperatures and aging.
- Synthetic oil: created from processed and controlled bases, which are more stable, cleaner, and more resistant over time.
Between the two, there are also semi-synthetics, often a compromise choice for not-too-modern engines.
⚙️ WHEN SYNTHETIC IS TRULY ESSENTIAL
In the workshop, we have no doubt: synthetic is mandatory when the engine design requires it.
- Modern engines with tight tolerances
- Turbochargers, where temperatures are high
- Cars with DPF or GPF, which require low SAPS oils
- Long change intervals
Using mineral oil on these engines means accelerating wear, clogging filters, and creating expensive problems.
🛠️ WHEN MINERAL STILL MAKES SENSE
Contrary to popular belief, mineral oil is not "bad oil." In some contexts, it still makes sense:
- Older engines, designed decades ago
- Presence of leaks: overly fluid synthetic oil can worsen them
- Occasional use (a few thousand km per year)
- Mild climates, without high thermal stress
On a tired engine, an "excessively good" oil often doesn't provide real benefits.
❌ COMMON MISTAKES WE SEE IN THE WORKSHOP
- Premium synthetic on a highly worn engine: increases consumption and leaks
- Mineral on engines designed for low SAPS: serious risk for DPFs and catalytic converters
- Random mixtures: mixing different oils without criteria
A typical mistake: thinking that "the more expensive, the better." In reality, compatibility with the engine is what matters.
❓ FREQUENTLY ASKED QUESTIONS
Does synthetic oil harm old cars?
No, not absolutely, but it is often useless or counterproductive on heavily worn engines.
Can I switch from mineral to synthetic?
Yes, but for older engines, it's better to evaluate on a case-by-case basis to avoid leaks.
Does mineral oil protect the engine less?
It protects less at high temperatures and over the long term, but can be adequate for light use.
Does the type or brand of oil matter more?
First the correct type, then the quality of the brand.
🏁 CONCLUSIONS
There is no universally best oil. There is only the right oil for that engine and for that type of use.
If you're wondering about the most reliable brand, not the type, you'll find a dedicated guide here:
