Good oil is the foundation of a healthy engine — without it, even the best unit won’t last long. At Parts4444, we see every day what people remove from their cars during dismantling, and half of the seized engines are the result of wrong oil or infrequent oil changes. In this guide, we explain without beating around the bush which oil to use, when to change it, and what to avoid — especially if you are installing a used engine from our warehouse.

Which engine oil should you choose?

In short: use oil that matches the manufacturer’s recommendations — viscosity, standard, and approval are listed in the service book. There is no point in experimenting, because every engine has its own requirements.

The correct oil for your engine can be found fastest in the owner’s manual or by VIN number. Three things matter: viscosity (e.g. 5W30, 5W40, 0W20), quality standard (ACEA, API), and manufacturer approval — VW 504.00, MB 229.5, BMW Longlife-04, dexos1, Ford WSS-M2C. For modern engines with DPF and turbo, use Low SAPS, low-ash oils — otherwise you will clog the particulate filter in a few months. Diesel engines with unit injectors (PD) require VW 505.01 approval — no discussion here. If you are installing a used engine from us, check what oil it previously ran on and do not mix different oil bases — always start with a fresh oil and filter change.

5W30 or 5W40 oil — which is better?

In short: 5W30 or 5W40 depends on the engine, mileage, and driving style. 5W30 is thinner at higher temperatures, 5W40 is thicker — and each has its purpose.

5W30 is now standard in modern cars from Europe, the USA, and Asia — lower fuel consumption, faster lubrication on cold start, and better compatibility with DPF and catalytic converters. 5W40 maintains a stronger oil film in high-mileage engines, powerful diesels, and turbocharged units that run hot on highways. If the car has 200,000+ km and starts consuming oil, 5W40 can often help by sealing gaps better. But do not change viscosity without reason — if the manufacturer specifies 5W30 with a specific approval, stick to it, because modern engines with variable valve timing systems (VVT, VANOS, VTEC) can develop faults with overly thick oil. In American engines from Chrysler, Dodge, Jeep, or Ford, 5W20 or 0W20 is often required — no improvisation here.

Synthetic or semi-synthetic oil — which to choose?

In short: in 9 out of 10 cases, choose full synthetic. Semi-synthetic is mostly suitable only for older high-mileage engines.

Full synthetic oil (PAO, ester, GTL) maintains performance in extreme temperatures, lasts longer, and reduces friction. Modern engines — turbo, common rail, downsizing 1.0–1.5 TSI/EcoBoost — are designed exclusively for synthetic oil, and semi-synthetic may lead to engine damage. Semi-synthetic oil (typically 10W40) still makes sense in older 1990s–2000s engines where synthetic oil may leak through worn seals. Mineral oils are outdated — used only in classic cars or during engine break-in after rebuild. If you install a used engine from our offer — use a high-quality synthetic oil with manufacturer approval and do a second oil change after 2000–3000 km as a “flush”.

How often should engine oil be changed?

In short: in real-world conditions, every 10,000–15,000 km or once a year, whichever comes first. Manufacturers often suggest 25,000–30,000 km, but that is too long.

Long-life intervals work only in mostly highway driving. In city traffic, short trips, and congestion, oil degrades much faster. Diesel engines with DPF in urban use should have oil changed every 10,000 km because fuel dilutes the oil during regeneration cycles.

Shorter intervals are needed in cases of:

• LPG/CNG operation;

• short trips and frequent cold starts;

• towing or heavy loads;

• aggressive driving and high RPM use;

• older turbocharged engines.

Always change the oil filter together with the oil and check air, cabin, and fuel filters as well. If you installed a used engine from Parts4444, the first oil change after 1500–3000 km is mandatory — it removes leftover deposits and contamination from the previous owner.

Best engine oil — brands you can trust

In short: the best engine oil rankings change yearly, but the same names stay at the top — Mobil 1, Castrol, Shell Helix, Total Quartz, Liqui Moly, Motul, Elf, Valvoline, and Pennzoil.

Mechanics commonly recommend Mobil 1 ESP/FS, Castrol Edge Titanium FST, Shell Helix Ultra, Liqui Moly Top Tec, and Motul 8100 X-cess. General breakdown by market:

Germany (Audi, BMW, Mercedes, Volkswagen, Porsche, Mini) — oils with VW 504.00/507.00, MB 229.51/229.52, BMW LL-04 approvals: Castrol, Mobil 1, Liqui Moly, Shell.
USA (Ford, Chrysler, Dodge, Jeep, Cadillac, Chevrolet, Lincoln, Buick) — Valvoline, Pennzoil Platinum, Mobil 1, often dexos1 or Ford WSS-M2C approvals.
Japan & Korea (Toyota, Lexus, Honda, Mazda, Subaru, Nissan, Mitsubishi, Hyundai, Kia) — OEM oils plus Idemitsu and ENEOS, mainly low-viscosity grades (0W20, 5W20).
Volvo, Land Rover, Jaguar — Castrol Edge and Shell Helix with proper approvals, often 0W30/0W40.

One warning — the oil market is full of counterfeit products. Buy only from trusted distributors or large platforms with verified sellers. Prices significantly below market level usually mean a fake product.

Oil and used engines — what to remember

In short: if you install a used engine, the first oil and filter change is mandatory — regardless of what the previous owner used.

At Parts4444, we have used engines, gearboxes, suspension parts, lights, hoods, fenders, bumpers, and many other components for Audi, BMW, Mercedes, Volkswagen, Toyota, Honda, Lexus, Acura, Jeep, Ford, Chrysler, Dodge, Cadillac, Chevrolet, Mazda, Subaru, Nissan, Volvo, Land Rover, Porsche, and many others — mainly imported from the USA. Each engine is inspected before shipping, photographed, and described honestly — no risk, no surprises. After installation, use fresh synthetic oil with manufacturer approval, replace the oil filter, and change oil again after 1500–3000 km. 

Not sure which oil fits your engine? Contact us via WhatsApp or call +48 459 567 444 — we will check it by VIN and advise immediately.