Gasoline (Otto cycle) vs Diesel engine differences: (1) IGNITION: gasoline uses SPARK IGNITION (spark plug fires the air-fuel mixture); diesel uses COMPRESSION IGNITION (high compression heats air to 700-900°F, sufficient to ignite injected fuel — no spark plug); (2) FUEL DELIVERY: modern gasoline uses port or direct injection; diesel always uses high-pressure DIRECT INJECTION (15,000-30,000+ psi) into the cylinder near top dead center; (3) COMPRESSION RATIO: gasoline 8:1 to 12:1 typical (higher would cause knock); diesel 14:1 to 22:1 (the high compression is essential for ignition); higher compression = more thermal efficiency; (4) FUEL: gasoline is more volatile (vaporizes easily); diesel is heavier oil-like fuel (slower-burning, more energy per gallon — about 10% more); (5) THROTTLE: gasoline engines control power by RESTRICTING AIR with throttle plate (varies air-fuel mixture); diesels typically have NO THROTTLE PLATE — control power by VARYING FUEL INJECTION amount; (6) POWER CHARACTERISTICS: gasoline peaks at higher RPM (5000-7000), produces more HP per liter; diesel peaks at lower RPM (2500-4500), produces more TORQUE per liter — great for heavy loads, hauling, low-end pulling; (7) FUEL ECONOMY: diesels typically 20-30% better fuel economy than gasoline (more efficient combustion + higher energy density of fuel); (8) EMISSIONS: diesel produces more NOx and particulates (soot); modern diesels require complex aftertreatment (DPF, SCR with DEF, EGR); gasoline produces more CO and HC; both meet modern standards with appropriate emission systems; (9) DURABILITY: diesel engines built sturdier for high compression and pressures; typically last longer (300,000-500,000+ miles common for diesel trucks); (10) COLD STARTING: diesels harder in cold (less volatile fuel); glow plugs preheat combustion chamber; cold-weather gelling of diesel fuel a concern in winter (winter blends with anti-gel additive); (11) APPLICATIONS: gasoline for most cars and light-duty trucks; diesel for heavy-duty trucks (semi-trucks, buses, vans), agricultural equipment, locomotives, marine, generators, some passenger cars (more common in Europe).
Turbocharging: nearly universal on modern diesels (atmospheric diesel is rare in modern vehicles); also increasingly common on gasoline engines; turbo uses exhaust energy to compress intake air → more air = more fuel = more power.
Maintenance: diesels need more frequent oil changes (combustion byproducts contaminate oil faster), fuel filter changes, DPF regeneration cycles, DEF refilling. Diesel fuel + gasoline engine = NO START (diesel doesn't vaporize); gasoline + diesel engine = ENGINE DAMAGE (lubricity issues, premature combustion timing, particulate damage to DPF). HCCI (homogeneous charge compression ignition) and other advanced combustion: experimental engines combining best traits of gasoline and diesel.