How to choose oil for a specific car model?

Choosing engine oil stirs up more debate than it deserves. Drivers ask about the brand, the price and whether a „better” oil really makes a difference — while the entire answer is already written in the car’s documentation, in just a handful of parameters. The right oil isn’t the most expensive one or the most heavily advertised; it’s the one that precisely meets your engine’s specification: the correct viscosity, the required manufacturer approval and the proper ACEA standard. This guide walks you through, step by step, how to establish those values, where to find them and how to avoid the mistakes that genuinely shorten an engine’s life.

Why matching the specification matters more than the brand

On the shop shelf, the difference between oils looks like a matter of prestige — a famous name against a cheaper alternative. In reality the engine never „sees” the logo on the bottle. All it responds to are the oil’s actual properties: how it behaves when cold, how it protects at high temperature and whether its additive package suits the design of the unit. Two oils from different brands that carry the same approval and viscosity are practically equivalent to the engine. Meanwhile an expensive, reputable oil without the correct approval can be a worse choice than a cheaper product that hits the manufacturer’s requirements exactly.

That is why the starting point should always be the service book and the owner’s manual, not a marketing slogan or a tip from an online forum. The engine’s maker tested specific oil specifications during development, and it is the manufacturer that knows what the unit needs to run trouble-free for years. Your only job is to read those requirements and follow them, rather than relying on intuition or the fashion for the „strongest” oil on the shelf.

The three parameters you must establish

The whole process comes down to a few numbers and codes. Once you know them, the choice becomes simple and the various brands turn into interchangeable options. So before you even look at the price, pin down these values for your model.

• SAE viscosity (e.g. 5W30) — tells you how thick the oil is when cold and when hot
• Manufacturer approval (e.g. VW 504.00, MB 229.51, BMW LL-04) — confirms it passed the brand’s own tests
• ACEA standard (e.g. A3/B4, C2, C3) — describes the quality class and additive content
• Any extra requirements — such as Low SAPS oil for cars fitted with a particulate filter

Viscosity is the first thing you look at. A marking such as 5W30 describes how the oil flows in the cold and inside a hot engine — pouring in something too thick or too thin makes starting harder or weakens the oil film. The manufacturer states the exact grade, or a few permitted ones, so there is no room for your own interpretation here.

The manufacturer approval is the most important of the three parameters. It is the brand’s own „certificate” that a given oil passed the tests of a specific make — Volkswagen, Mercedes or BMW, for example — and is fit for its engines. An approval outranks the ACEA standard alone, because it is often stricter and accounts for the quirks of a particular design.

The ACEA standard sorts oils by quality class and intended use. The A/B classes cover classic petrol and diesel engines, while the C classes are meant for units with a particulate filter and catalytic converters that need a reduced ash content. When the manual gives a specific ACEA class, treat it as a minimum you must never go below.

Where to find the right specification — step by step

Working out what your own car needs takes a few minutes and no mechanic’s knowledge. Just follow the order from the most reliable source to the one that merely confirms the result.

1. Open the owner’s manual and find the section on operating fluids — that is where the required viscosity and approval are listed
2. Check the manufacturer’s website with an oil finder by VIN — it returns the specification for your exact car
3. Look through the service book — the oil used at previous changes is sometimes recorded there
4. Search for stickers and markings in the engine bay or on the oil filler cap
5. If in doubt, consult a mechanic who knows your model rather than guessing

If the sources list several permitted viscosities, pick the one recommended for your climate zone — in most of Europe that means 5W30 or 5W40. When the manual names both an ACEA standard and a brand approval, the approval takes priority. Never drop below the stated quality minimum, even if a cheaper oil „technically fits” on viscosity alone.

Petrol, diesel or LPG — what the fuel type changes

The type of engine and fuel affects the demands placed on the oil, though always within the limits set by the approval. Petrol engines without a particulate filter usually run on ACEA A/B class oils of the right viscosity. Modern diesels, almost always fitted with a DPF, require C class oils with a reduced ash content that will not clog the filter during regeneration.

Cars with an LPG system are a special case. Running on gas raises the temperature in the combustion chamber and loads the oil more heavily in thermal terms, so it pays to stick to a product with a strong additive package and a fully synthetic base that strictly matches the approval. The rule stays the same: a gas installation does not exempt you from choosing oil by the engine maker’s specification — it simply makes cutting corners on quality even less worthwhile.

Cars with a DPF — why Low SAPS oil is mandatory

A particulate filter is one of the most expensive parts of the exhaust system, and the wrong oil can block it for good. During regeneration some oil reaches the exhaust and burns off — if it contains a lot of sulphated ash, phosphorus and sulphur, those deposits settle in the filter and gradually choke it. That is why cars with a DPF require Low SAPS oils, meaning ones with a reduced content of those compounds, marked with the ACEA C class.

The right oil isn’t the most expensive oil, but the one that matches your engine’s specification — its viscosity, approval and ACEA standard at the same time.

The most common mistakes when choosing oil

• Going by brand or price alone instead of approval and viscosity
• Pouring in a „universal” oil without checking the requirements of the specific model
• Downgrading the quality class to save money — for example an oil without the required C standard in a car with a DPF
• Trusting a forum tip instead of the manual and the service book
• Topping up with a random oil of a different viscosity and treating that as the norm

What else to check before a change

Matching the specification isn’t the whole story — how often you change the oil and the conditions you drive in matter just as much. The manufacturer lists a recommended interval in the service book, but that figure assumes average use. Driving mostly on short trips, around town, with frequent cold starts or on LPG shortens the oil’s real service life, because it never gets hot enough to boil off moisture and fuel. In those conditions it is worth shortening the interval, even if the oil could „formally” still run.

At every change, also check that the oil you have chosen agrees with what is already in the engine — if a previous service poured in a product of a different viscosity or without the required approval, this is a good moment to return to the correct specification. Always pair the change with a new oil filter; the old filter holds contaminants from the previous period and partly cancels out the benefit of fresh oil. Only the full set — the right oil plus a new filter — gives the engine complete protection.

Can I use an oil with a different viscosity than recommended?

In an emergency, topping up with an oil of a similar viscosity will not destroy the engine — it is better to add a properly matched product than to drive on too low a level. In the long run, though, stick to the grade stated by the manufacturer. Oil that is too thick makes cold starts harder and reaches the components more slowly after start-up, while oil that is too thin may fail to hold an adequate film at high temperature. If the manual permits several viscosities, choosing between them is safe; stepping outside that list is not.

How do I know which approval my car requires?

The most reliable source is the owner’s manual in its operating-fluids section, together with the oil finder by VIN on the manufacturer’s website. Approvals are written as brand codes such as VW 504.00, MB 229.51 or BMW Longlife-04. If you have no access to the documentation, a mechanic can establish the approval code from the make, model, year and engine type. Never guess — the gap between two similar-looking approvals can be wider than it seems.

Does a car running on LPG need a special oil?

There is no separate „LPG standard”, but running on gas loads the oil more heavily in thermal terms, so it is worth choosing a product with a strong additive package that strictly matches the engine maker’s approval. In practice that usually means a good-quality fully synthetic oil of the required viscosity and approval. The engine’s specification remains decisive — the gas installation does not change it, it only makes skimping on oil quality more likely to backfire.

Is a more expensive oil from a famous brand always better?

No. Quality is decided by compliance with the specification, not by price or logo. A cheap oil with the correct approval and viscosity is a better choice than an expensive product that lacks the required standard. Pricier oils often carry richer additive packages and meet several approvals at once, which can help in modern, heavily loaded engines — but a high price on its own guarantees nothing if the oil does not match your car’s requirements.

What happens if I put in the wrong oil?

The consequences depend on the scale of the error. A minor deviation may go unnoticed, but a seriously mismatched oil can show up as a noisier engine, harder cold starts, a faster drop in level or the oil pressure warning light coming on. In a diesel without the correct C standard you genuinely risk clogging the particulate filter. If something clearly changed for the worse after a change, the best move is to swap the oil for one that exactly matches the manufacturer’s approval as soon as possible.

Would you rather not dig into this? Give us the make, model, year and engine type of your car, and we will select an oil that precisely matches its specification — the right viscosity, approval and ACEA standard — and change it with a call-out to your address. You will find the scope and prices in our price list.