Aramco, the Saudi Arabian state-owned oil company, has developed a Dedicated Hybrid Engine, or DHE, that rethinks how combustion and electric power can work together. The powertrain is designed from scratch rather than adapting an existing engine for hybrid duty, and it arrives as hybrid sales outpace battery-electric vehicles in some regions. Aramco has a clear interest in keeping gasoline engines relevant — and customers lining up at pumps.
The company already has a stake in Horse Powertrain, a joint venture formed when Renault and Geely spun off their combustion-engine operations. It owns 10 percent of that business, which supplies turnkey hybrid and range-extender systems. The DHE project goes a step further, asking what a purpose-built hybrid powertrain might look like if engineers ignored legacy designs and started over.
An Engine Without a Separate Cylinder Head
The initial proof-of-concept uses a 1,599cc inline three-cylinder engine. It is a cam-in-block pushrod design with a monoblock casting — no separate cylinder head. The engine uses just two valves per cylinder, with no variable timing or lift. To cut friction, there are no journal bearings. The crank, camshaft, and connecting rods ride on roller bearings, and the crank is offset 12 millimeters from the bore centers to reduce piston side loading. There is no accessory drive; the water pump and other auxiliaries run electrically on demand.
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Aramco claims thermal efficiency in the 41–42 percent range. The combustion chamber is undersquare — an 82-mm bore and 101-mm stroke — to reduce surface-to-volume ratio and limit heat loss. The design uses high-tumble, low-swirl intake with both direct and port injection. A late intake-valve closing strategy keeps effective compression lower while preserving the full expansion ratio, and cooled EGR cuts throttling losses at light loads.
The Engineer Behind the Project
The DHE is being developed at Aramco Americas Detroit Research Center by Nayan Engineer. He previously ran a gasoline direct-injection compression-ignition program at Hyundai — one of several efforts, alongside Mercedes-Benz DiesOtto and General Motors HCCI, that ultimately failed to deliver diesel-like fuel economy at acceptable cost and emissions. His small team conceived the engine, and French motorsport builder Pipo Moteurs developed it and produced two running prototypes now undergoing testing.
That history matters. The auto industry has spent billions trying to reinvent the combustion engine, and most of those programs were canceled. Aramco is betting its clean-sheet approach can succeed where others couldn’t, largely by keeping the mechanical design simple.
Two Planetary Gears Instead of One
The electric side of the powertrain mirrors Toyota’s Hybrid Cooperation Drive but doubles the hardware. Each end of the crankshaft connects to the planet carrier of an epicyclic gearset. The sun gear on each side attaches to a motor that functions primarily as a generator, and the outer ring gear connects to a primary traction motor geared to the wheels. With two planetary arrangements, there is no need for a differential. The engine and planetary gear sets share a common lubricant.
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The setup allows the car to run with the engine on or off, making it suitable for both conventional hybrids and plug-in hybrids or range-extender applications. Future upgrades to axial-flux traction motors could shrink the overall width further.
Claims on Cost and Fuel Savings
Eliminating the cylinder head drastically cuts machining costs. Engineer’s parts count for the naturally aspirated inline-three is just 175. A comparable Toyota Prius four-cylinder engine has significantly more parts, though the team is still finalizing that comparison. The roller bearings and dual planetary gear sets add cost, but Aramco argues that using smaller motors with fewer rare-earth magnets offsets some of that expense.
The company’s calculations suggest a naturally aspirated I-3 DHE could deliver a 35 percent drop in fuel consumption at an upcharge of $3,800 relative to a conventional port-injected DOHC four-cylinder in a midsize sedan. A naturally aspirated V-6 version would offer similar fuel savings for $4,080 in a midsize SUV. Aramco says that represents a few percentage points more fuel savings at roughly 20-plus percent less cost than a power-split hybrid like Toyota’s HSD.
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Those figures come from their own modeling and have not been independently verified. The company has a vested interest in making the numbers look favorable.
A Modular Family and Early Interest
The design is modular. Engineer envisions a range of engines using the same combustion chamber: a 1.1-liter parallel two-cylinder, a 2.1-liter V-4, and a 3.2-liter V-6 — the V engines essentially bolt two monoblocks together. Each would be available in naturally aspirated or turbocharged configurations. A longitudinally mounted mid-engine layout could drive all four wheels, taking advantage of the dry-sump lubrication system to lean the engine over and fit under a low floor.
The SAE World Congress session covering the DHE in 2026 drew a full house. U.S. patent number U.S. 12,558,950 B2 was only granted on February 24 of this year, and Aramco has just begun shopping the design around. No automakers have publicly signed on yet.
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