Engine deep-dive · Japan

Kubota D722 Diesel

The Japanese 3-cylinder diesel powering professional groundskeeping

Family3-cylinder vertical diesel — ride-on and commercial out-front

Displacement719cc

Torque32.5 ft-lb

ArchitectureLiquid-cooled 3-cylinder indirect-injection diesel

Typical life8,000–10,000 hours (30+ years of domestic use, 15+ years commercial)

The story of this engine

The D722 is Kubota's most-fitted small diesel and the engine that powers the G21-series and earlier G23 ride-on mowers, the BX1880 sub-compact tractor, plus thousands of generators, compressors and small forklifts across the UK. A 30-year-old D722 with documented oil changes will outrun the rest of the host machine. Service parts are universal and available everywhere Kubota dealers exist.

Why owners like it

8,000-hour service life is realistic with annual oil change and clean fuel
Common-rail fuel injection and 12V starter — no glow plugs to fail
Parts continuity is the strongest in the small-diesel market via Kubota dealers
Genuine smoke-free running on clean ULSD if service intervals are honoured

Where it falls short

Eye-watering cost in host machine — diesel premium over petrol equivalents
Diesel filter is the single most-important service item — owner-skip costs £400
Older D722 units lack DPF — newer emissions zones may restrict use
Cold starts demand a fully charged battery — diesels are unforgiving of weak batteries

Service intervals & costs

What this engine actually needs every year, and what it costs to keep alive.

Interval	Task	Cost
Every 100 hours	Engine oil change — 15W-40 diesel-spec	£18 DIY / £90 dealer
Every 100 hours	Oil filter	£15 OEM
Every 200 hours	Fuel filter — non-negotiable	£25 OEM
Every 200 hours	Air filter element	£35 OEM
Every 800 hours	Injector inspection and clean	£0 DIY (basic check) / £180 dealer service
Every 2000 hours	Coolant flush and replace	£25 OAT coolant

What goes wrong, and when

Every engine family has predictable failures by age. Knowing what's coming saves money on used buys and makes negotiation easier.

Years 1–8 (under 1500hr)

None expected with proper service. The D722 is genuinely fault-free if oil and filters are maintained.

Years 8–15 (1500–3500hr)

Fuel filter neglect is the most common failure mode. Symptom: power loss on hot day, hard restarting. £25 fix if caught early; £400 injector pump rebuild if ignored.

Years 15–20 (3500–6000hr)

Glow plug or relay drift — though some D722s skip glow plugs entirely. Symptom: hard cold starts. £45 glow plug pair, 30-minute DIY job.

Years 20+ (6000hr+)

Injector spray pattern degrades, smoke under load increases. Dealer injector overhaul £200–£300 per cylinder. Engine still has 2000–3000 hours after rebuild.

Parts cost reference

UK 2026 prices — OEM (genuine) vs aftermarket. Generic parts work fine on consumables; stick to OEM on anything that affects timing or tolerance.

Part	OEM	Aftermarket
Oil filter	£15	£8
Fuel filter	£25	£12
Air filter element	£35	£18
Glow plug pair	£45	£22
Injector rebuild kit (per cyl)	£85	—
Replacement engine (used 4000hr)	£1800	—

The verdict

The diesel engine that defines the small commercial-mower category in the UK. 30-year service horizon is realistic on a domestic-use D722. The cost premium over a petrol equivalent recovers inside three seasons of commercial mowing. For domestic users, only the engine to specify if you want a mower for the rest of your life.