Honda K20C

Honda's 2.0 VTEC Turbo — the Civic Type R's engine, and in lower states of tune the Accord's and the Acura RDX's.

It is a direct-injected turbocharged four and shares its diagnosis with every other one, which is the useful thing to say to somebody arriving from the older naturally aspirated K-series: intake-valve carbon is expected at mileage rather than a fault, because no fuel washes over the valves to keep them clean.

Fuel dilution of the oil is a known pattern on the lower-output versions in cold, short-journey use — the RDX and Accord rather than the Type R — and it presents as a rising oil level and a fuel smell from the dipstick. The remedy is use and interval, not a part.

The turbocharger's life tracks oil condition, and on an engine making this much power per litre that is not routine advice: it is the failure mode.

It is not the older K20A or K24, and almost nothing about those transfers — different block, different head, different management, and a K24 page exists here separately for the naturally aspirated family.