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Oil change

Choose the right engine oil (viscosity and specification)

Guide to viscosity (5W-30, 0W-20 etc.) and specification (ACEA, API, VW 504/507, MB Approval). How to avoid engine damage and warranty loss.

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Choose the right engine oil (viscosity and specification)
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Why is choosing the right engine oil so important?

Engine oil isn't just "something you pour in" — it is a highly developed lubricant designed for your specific engine's construction, operating temperatures, driving pattern and emission requirements. Using the wrong oil can lead to anything from slightly higher consumption and marginally reduced performance to oil pump failure, undue wear on the timing chain and total engine failure. On modern cars the wrong oil can also clog the particulate filter or damage the emission system. And — importantly — wrong oil on a car under factory warranty can void the warranty, not only for the engine but for all related components.

Viscosity — the first and second numbers

Multigrade oils carry a code like "5W-30" or "0W-20". Both numbers have meanings of their own:

  • First number + W (Winter): the oil's viscosity at cold start. Lower number = better cold flow. 0W flows best in cold, 20W the least (you rarely see 20W in modern cars in Norway). A 0W oil can start the engine at -40 °C without problems.
  • Second number: the oil's viscosity at 100 °C operation. Lower number = thinner at operating temperature, giving lower fuel consumption. Higher number = thicker, giving better protection under heavy load. 20 is thin and gives best consumption; 50 is thick and used in sports cars and hard-working engines.

Common combinations in Norway: 5W-30 (most common in modern cars), 0W-20 (required by Toyota Hybrid, many Volvo and some Ford), 5W-40 (heavy load, sport, older cars), 10W-40 (older cars, budget cars).

Specifications — ACEA, API and factory approvals

Viscosity alone is not enough — the oil must also meet certain specifications that describe what additives it contains, how well it resists oxidation, how low its ash formation is, and so on.

ACEA (European standard)

  • A1/B1, A3/B3, A3/B4, A5/B5 — petrol/diesel without particulate filter
  • C1, C2, C3, C4 — low-SAPS for cars with particulate filter (DPF)
  • E4, E6, E7, E9 — heavy diesel (truck, bus)

API (American standard)

  • SN, SP — modern petrol engine (SP is the latest)
  • CK-4, CJ-4 — modern diesel engine

Factory approvals

  • VW 504 00 / 507 00 — Volkswagen group, long-life service
  • MB 229.5 / 229.51 / 229.52 — Mercedes-Benz
  • BMW Longlife-01 / -04 — BMW
  • GM Dexos1 / Dexos2 — Opel, Chevrolet, GM
  • Ford WSS-M2C913 / -M2C950 — Ford

Consequences of the wrong oil

  • Oil too thin: insufficient oil film between wear surfaces, increased wear on bearings and camshafts, reduced oil pressure
  • Oil too thick: poor cold-start flow, higher fuel consumption, extra load on the oil pump
  • Wrong specification on a DPF car: clogged particulate filter — cleaning or replacement may cost NOK 30,000–60,000
  • Wrong oil on a car with timing chain: excessive chain wear, may end in chain failure and total engine destruction
  • Warranty loss: every manufacturer requires the correct specification — wrong oil is immediate grounds to reject a warranty claim

How to find the right oil for your car

  1. Owner's manual: the best source, shows both viscosity and specification
  2. Oil filler cap under the hood: some cars have the specification directly on the cap
  3. Online oil selector: Castrol, Mobil and Shell have free tools where you enter the registration number or car model
  4. Ask the workshop: we have access to full production history and specifications for every brand — we find the right oil in minutes

When you book an oil change with us we always check the car's specification requirement in our workshop system before choosing the oil. That's your guarantee that we put in the oil the manufacturer actually specified — not the one that happens to be cheapest on the shelf.

Book an oil change online or call us on 41 17 32 24.

Frequently asked questions

What is the difference between 5W-30 and 0W-20?

5W-30 and 0W-20 are both multigrade oils for modern cars. The difference is that 0W-20 is thinner both at cold start (0W vs 5W) and at operating temperature (20 vs 30) — that gives lower fuel consumption and better cold start, but your car MUST have been designed for such a thin oil. Toyota Hybrid and many new Japanese cars require 0W-20. 5W-30 is still the most common choice for modern European cars. Never use 0W-20 if the car is specified for 5W-30 or thicker.

What does ACEA C3 mean?

ACEA C3 is a European classification for low-SAPS oil (low Sulphated Ash, Phosphorus, Sulphur). C-classes are intended for cars with a particulate filter (DPF) — typically modern diesels. C3 is a balanced choice usable for most DPF cars, both petrol and diesel, and is the most common option in the range. Many factory specs (MB 229.51, BMW LL-04, etc.) are built on ACEA C3 as a base.

Can I use cheaper oil?

It depends on what you mean by "cheaper". If you are comparing two oils both of which have the correct viscosity and meet your factory specification, they are technically equivalent — you can safely choose the cheaper one. But if "cheaper" means oil without the right specification (e.g. ACEA A3 instead of C3 on a DPF car), you risk engine damage, warranty loss and expensive repairs. The 100–200 NOK saving isn't worth the risk.

Where do I find the right oil specification for my car?

The best source is the owner's manual — it shows both viscosity and specification. Other sources: the oil filler cap under the hood (many cars carry the spec there), online oil selectors from Castrol, Mobil or Shell where you enter the registration number, or just ask us at the workshop. We have access to full production history and find the right oil in minutes.

What happens if I used the wrong oil?

Depends on how long and how wrong. A single fill with slightly wrong viscosity is rarely critical — switch to the correct oil at the next change. A longer period with the entirely wrong oil may have caused wear or ash buildup in the particulate filter that takes time to recover from. Recommendation: switch to the correct oil immediately and book an engine diagnosis if you have concerns. We can also evaluate oil samples to check engine wear.

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