Tankers are under more pressure than most ships right now. Carbon costs are rising, efficiency ratings tighten every year, and owners are still arguing about which fuel to order next. All of that lands in one place: the engine room. So what tanker engine is actually down there?
Start with a correction. The photo you’ve probably seen of the “world’s biggest tanker engine”, with 14 cylinders, over 2,300 tonnes and a crowd of engineers for scale, isn’t a tanker engine. It’s the Wärtsilä-Sulzer RTA96-C, an engine designed for large container ships. The 14-cylinder version, rated at 80,080 kW, entered service on the Emma Mærsk in September 2006. Tanker engines are big, but they’re built for a different job.
This guide covers what powers a tanker from an MR to a VLCC, who builds those engines, what else runs in the engine room, what wears out, and which 2026 rules affect how you run it.
The short answer
Almost every ocean-going oil tanker has the same basic layout:
- One main engine: a slow-speed, two-stroke diesel, coupled directly to the propeller shaft with no gearbox. According to WinGD’s published ranges, it turns at roughly 58 to 105 rpm, depending on its size and rating.
- Usually three auxiliary engines (gensets): medium-speed four-stroke diesels running at 720 to 900 rpm, which drive generators for the ship’s electrical load.
- An emergency generator: a small high-speed diesel.
- Boilers: oil-fired auxiliary boilers plus an exhaust gas boiler. On crude carriers, the boilers make steam for the cargo pumps.
- Turbochargers: one or more on the main engine and one on each genset.
That’s the theory. In practice, the details change with the size of the ship, its age and the cargo it carries.
Who builds tanker engines?
Big question, short answer: two companies design almost all the large two-stroke engines that drive tankers.
Everllence was called MAN Energy Solutions until June 2025, when the company took its new name. Its two-stroke engines are now marketed as Everllence B&W, but anything built earlier will say MAN B&W on the nameplate and in the manuals. In June 2026, Volkswagen agreed to sell a 51% stake in Everllence to Bain Capital and keep the rest. Completion was expected by the end of 2026, subject to approvals. Everllence’s own statement at the time of the rename was that the product and service portfolio would not change.
WinGD carries on the Sulzer two-stroke line. That’s the same family as the RTA engines (introduced in 1983) and the RT-flex (the first one entered service in 2001), which you’ll still find on many older tankers. In July 2026, WinGD won an order for 12 VLCC engines, each a 6X82-2.0, for Dynacom ships being built at Hudong-Zhonghua in China.
Both designers license their engines to builders, so the company that cast your engine block is often not the one whose name is on the design. For spare parts and service, that matters. The part number and the engine maker’s documentation are what count, not the logo on the crate.
How to read an engine name
The engine name on the plate tells you more than you might expect. Take 6G70ME-C10.5: six cylinders, G-type (Everllence’s ultra-long-stroke design), a 70 cm bore, ME-C electronic control, and Mark 10.5, which is the design version. WinGD names follow the same logic: 6X82-2.0 is six cylinders, the X series, an 82 cm bore and version 2.0. A DF in the name means dual-fuel, and DF-A means the ammonia version.
If you remember one number from the name, make it the bore. It tells you roughly what size of ship the engine was built for.
Tanker engine by ship size
Tanker sizes are usually given on the AFRA scale, which sorts ships by deadweight tonnage (DWT). According to the US Energy Information Administration, an MR tanker is 25,000–55,000 DWT, an LR2 is 80,000–160,000 DWT and a VLCC is 160,000–320,000 DWT. “Aframax” and “Suezmax” are trade names that overlap the LR2 band, and the largest Suezmaxes go above it.
| Tanker class | Typical engine bore | Real examples | Power range of that engine family (maker data) |
|---|---|---|---|
| MR product/chemical tanker (25,000–55,000 DWT) | 50–52 cm | MAN B&W 6G50ME-C9.6 on a 49,900 DWT methanol dual-fuel MR (built at GSI, China, for delivery in 2022) | WinGD X52: up to 14,480 kW at 79–105 rpm |
| Aframax / LR2 (about 80,000–120,000 DWT) | 60–62 cm | Six-cylinder WinGD X62DF-A (ammonia dual-fuel) for AET’s Aframax tankers built at Dalian | WinGD X62: up to 23,200 kW at 77–103 rpm |
| Suezmax (about 120,000–200,000 DWT) | 70–72 cm | MAN B&W 6G70ME-C10.5 with one TCT60 turbocharger on 158,000 DWT Suezmaxes (turbochargers ordered 2020, Daehan, Korea) | WinGD X72: up to 28,880 kW at 66–89 rpm |
| VLCC (160,000–320,000 DWT) | 80–84 cm | MAN B&W 7S80MC, 25,485 kW at 79 rpm (delivered 2000); Sulzer 7RTA84T-B, 27,160 kW at 74 rpm (delivered 2003); WinGD 6X82-2.0 (ordered July 2026) | WinGD X82-2.0: 16,560–49,500 kW at 58–84 rpm |
Two points about this table. First, the power ranges cover every cylinder number and rating the maker offers. A real ship is usually specified well below the maximum. Second, the two VLCC examples from 2000 and 2003 are deliberate: ships of that vintage can still be trading, and their engines have been out of production for years. Parts for those engines come from documentation and part numbers, not from a current catalogue.
Why tankers use slow two-stroke engines
Why not something smaller and faster with a gearbox? Because a big, slow propeller is efficient, and a slow two-stroke engine can drive one directly. No gearbox means one less large component to fail and fewer losses between fuel and thrust.
The trend is towards even slower engines. When MAN launched its G-type engines in 2010–2011, it said the longer stroke would allow a bigger propeller and estimated 4–7% lower fuel consumption. That’s the maker’s own estimate, made at launch. The actual saving depends on the hull, the propeller and how the ship is sailed.
On fuel, WinGD publishes a specific fuel consumption of 165.3 g/kWh for the X82-2.0 at full rating. What does that mean per day?
Imagine a VLCC main engine running at 15,000 kW for 24 hours at about 170 g/kWh. That’s 15,000 × 24 × 0.170 = 61,200 kg, or about 61 tonnes of fuel a day. Treat that as arithmetic, not a measurement: speed, draught, weather, hull fouling and fuel quality all move the real figure.
The rest of a tanker’s engine room
This is where tankers differ from bulk carriers and container ships, and where most guides stop too early.
Auxiliary engines (gensets)
Gensets are medium-speed four-strokes that run all the time, at sea and in port. Two published VLCC specifications show the usual pattern. A 310,000 DWT VLCC delivered in 2000 had three 980 kW diesel generators running at 720 rpm, plus a 400 kW emergency generator. A 300,000 DWT VLCC built in 2003 had three Wärtsilä 9L20C gensets of 1,490 kW each at 900 rpm, plus a 399 kW emergency set.
Three gensets is not luxury. It lets you run one or two while the third is opened up for maintenance, which is exactly why a genset that’s been “almost due” for a year becomes a problem.
Boilers and cargo pumps
Here’s the tanker-specific part. On a traditional crude carrier, cargo pumps in a pump room are driven by steam turbines. The 2000-built VLCC above discharged with three Shinko steam-turbine pumps, each rated at 5,000 m³/h with 150 m of head. The 2003 VLCC carried two oil-fired boilers (55 tonnes of steam per hour), plus an exhaust gas boiler.
Here’s what that means in practice: during discharge, the main engine is stopped but the boilers and gensets are working at their hardest. A tanker’s busiest machinery day is often in port.
Product and chemical tankers usually work differently. They have one submerged cargo pump in each tank, typically hydraulically driven, for example by Framo systems. That removes the pump room and keeps cargoes segregated. The engine-room job changes too: instead of a steam plant, you look after hydraulic power packs.
Turbochargers
A two-stroke main engine depends on its turbocharger for scavenge air. With the turbocharger out of action, it can only run at much reduced power. The Suezmaxes in the table carry one turbocharger per engine, so there’s no redundancy to fall back on. Accelleron’s A100-L/A200-L series covers low-speed engines from 3,000 to 28,000 kW and reached its 10,000th order in March 2026.
Turbocharger servicing is also changing. In April 2026, Accelleron launched its ACCX300-L, designed so the whole rotating assembly can be swapped during a port stay. Accelleron says this cuts scheduled service events from four to three over a 25-year ship life. That’s a maker’s claim for a new product, so it’s too early to have independent service data.
What wears out, and what to plan for
Can we give you a universal overhaul interval? No, and you should be wary of anyone who does. Intervals come from the engine maker’s maintenance schedule and change with fuel quality, load profile and how the engine has been treated. What we can give you is where the work usually is.
| Component | Engine | What happens | What to plan |
|---|---|---|---|
| Cylinder liners, piston rings, piston crowns | Main engine | Wear, scuffing, cracked crowns | Regular scavenge port inspections; liner calibration records you can show |
| Exhaust valves and fuel valves | Main engine | Burnt seats, poor atomisation | Reconditioned spares on board; correct part numbers for the engine’s Mark and version |
| Crankshaft journals and bearings | Main and auxiliary engines | Scoring after lube oil problems | Survey and in-situ machining instead of removing the crankshaft, where class accepts it |
| Turbocharger rotor, bearings, nozzle ring | All engines | Fouling, bearing wear, imbalance | Overhaul and dynamic balancing, or an exchange unit timed to the port call |
| Genset cylinder heads and bearings | Auxiliary engines | High running hours from port and cargo loads | Rotate overhauls so two sets are always available |
| Cargo pump drives | Steam turbines or hydraulic power packs | Wear that shows up during discharge | Check before arrival, not when the terminal is waiting |
Imagine the vessel is due to sail in eight hours, and the chief reports that one genset is down and a second is running hot. Who decides whether she sails? In practice, it’s whoever is under the most time pressure. The way to avoid that call is to plan the third genset’s overhaul before it becomes urgent.
Melbridge carries out main and auxiliary engine overhauls, in-situ crankshaft machining and turbocharger overhauls on board or in the workshop. That covers MAN B&W, Wärtsilä and Sulzer engines among others. Reconditioned turbochargers are tested before delivery and carry a minimum six-month guarantee. For parts, see engine and turbocharger spares.
What the 2026 rules mean for your tanker engine
None of these rules tells you which engine to install. All of them affect how you run the one you have.
| Rule | What applies | Effect on the engine room |
|---|---|---|
| EEXI (IMO, since 1 January 2023, ships of 400 GT and above) | A one-off energy efficiency check on existing ships | Many older tankers met it with engine or shaft power limitation, which caps available power below the original rating |
| CII (IMO, ships of 5,000 GT and above) | Required reduction of 11% versus 2019 for 2026, rising to 21.5% by 2030 (MEPC 83, 2025) | An engine in poor condition burns more fuel and pulls the rating down every year |
| EU ETS (EEA voyages, 5,000 GT and above) | In 2026, allowances are due for 70% of 2025 emissions; for 2026 emissions, the figure is 100%. Methane and N₂O are covered from 1 January 2026 | Every extra tonne of fuel now has a carbon cost on EU voyages; methane slip counts for gas-fuelled engines |
| IMO Net-Zero Framework | Not yet adopted; adoption is now being attempted in December 2026 | The fuel choice for newbuild engines stays uncertain until it’s settled |
| North-East Atlantic ECA (NOx, SOx, particulates) | Enters into force on 1 September 2027 (adopted at MEPC 84) | Tier III NOx limits for new ships trading there; engines need SCR or an equivalent system |
On EEXI: under the IMO’s EEXI and CII rules, power limitation is an approved way to comply, and shipowners favoured it because it was simple and cheap. The trade-off is less power in reserve, so the condition of the engine and its turbocharger matters more, not less.
On the EU ETS: EMSA’s phase-in schedule sets out the phase-in steps, with full coverage from 2027. We cover the cost side in EU ETS in 2026: full compliance is here.
On the Net-Zero Framework: in October 2025, IMO member states voted 57 to 49 to adjourn the adoption for a year. At MEPC 84 (27 April to 1 May 2026) the framework survived, and another adoption attempt is planned for December 2026. Until then, any dual-fuel decision is a bet on where the rules will land. That’s why new tanker orders are split between conventional engines, methanol (Everllence reports more than 600,000 operating hours on its ME-LGIM engines) and ammonia (WinGD’s X-DF-A).
FAQ
What engine does an oil tanker use?
Almost always a slow-speed two-stroke diesel main engine coupled directly to the propeller, designed by Everllence (formerly MAN Energy Solutions) or WinGD, which carries on the Sulzer two-stroke line. Medium-speed four-stroke gensets supply electrical power.
How powerful is a VLCC engine?
Two published VLCC specifications from 2000 and 2003 list main engines of 25,485 kW and 27,160 kW. WinGD’s current X82-2.0, which it designed for VLCCs, covers 16,560 to 49,500 kW, depending on the number of cylinders and the rating.
How many engines does a tanker have?
Typically one main engine, three diesel generators and one emergency generator. Crude carriers also have steam turbines driving the cargo pumps, and product tankers usually have hydraulic power packs.
Is a tanker engine two-stroke or four-stroke?
Both. The main engine is a two-stroke, while the gensets are four-strokes running at 720 to 900 rpm in the examples above.
What is the biggest ship engine in the world?
The 14-cylinder Wärtsilä-Sulzer RTA96-C at 80,080 kW, which is a container-ship engine, not a tanker engine. It first entered service in 2006.
How much fuel does a tanker engine burn per day?
It depends on speed and load. As a worked example, a main engine at 15,000 kW for 24 hours at about 170 g/kWh burns roughly 61 tonnes. Your noon reports are the only figure that counts for your ship.
The main message
A tanker engine room is one system: the main engine moves the ship, and the gensets, boilers and pumps move the cargo. Plan maintenance for all of it, because the part that stops you is rarely the one everyone is watching.
Need a hand with a main engine, genset or turbocharger? Send the engine type, the job and the next port to Melbridge, and we’ll tell you what we can do and when.
