Caterpillar 621K vs Caterpillar 631K

	Caterpillar Caterpillar 621K	Caterpillar Caterpillar 631K
Operating weight	—	—
Engine power	—	—
Heaped capacity	≈18 m³ (24 yd³)	≈26 m³ (34 yd³)
Rated load	≈22,000 kg (48,500 lb)	—
Engine	Cat C13	—
Configuration	Single engine, open bowl	Single engine, open bowl
Strengths	+ Versatile mid-size capacity + Lower cost than twin-engine models + Cat dealer support	+ High capacity + Fast haul speeds
Watch-outs	− Needs a push dozer to load fully	− Needs push loading
	Full 621K review	Full 631K review

Specifications are typical figures for standard configurations and may be measured differently by each manufacturer (for example net vs gross power). Always confirm with the manufacturer or dealer. Build another comparison.