Honda R-series

Honda's 1.8 and 2.0 litre economy fours — the engine of the eighth- and ninth-generation Civic and of the CR-V, sitting below the K-series in the range and designed for efficiency rather than output.

The R18's distinguishing feature is an unusual form of i-VTEC that delays intake valve closing at light load to reduce pumping losses, effectively running an Atkinson-like cycle in cruise. That is worth knowing because it makes the engine's part-load behaviour and fuel trims look different from a conventional Honda four, and a fuel-trim reading interpreted by K-series expectations can mislead.

In service they are durable and undramatic. The complaints that recur are the VTEC spool valve screen and solenoid — clogged by neglected oil and producing a performance complaint with a system-level code — plus ignition coils and, at high mileage, valve clearance drifting out of specification. Honda engines of this era genuinely need their valve clearances checked, and a ticking or a misfire on a high-mileage R-series is often exactly that.