Petrol in the oil on the 1.5 turbo

Fuel works its way past the rings into the sump, the oil level rises, and the oil stops being oil. Honda extended the powertrain warranty on affected cars to 6 years with no mileage limit and pushed a software update — a bigger response than a bulletin usually gets. Two model years for the CR-V, three for the Civic, and both ranges are narrower than the story's reputation.

Symptoms

Honda's bulletins describe it through the codes rather than the cause: misfire on one or more cylinders (P0300–P0304) or "fuel system too rich" (P0172), plus "a whirling noise coming from the engine compartment". What an owner usually notices first is simpler — the oil level on the dipstick is above full and the oil smells of petrol.

Likely cause

Honda's own service bulletins do not use the phrase. The company's memo to NHTSA of 31 January 2019 does, naming "engine oil dilution" directly and pointing at the same bulletins. Unburnt fuel gets past the piston rings into the sump — which is why cold weather and short journeys make it worse: the engine never gets hot enough for long enough to boil the fuel back out.

How should it be checked?

Two different remedies, and a car may have had one, both or neither. The software update was sent as a product update in December 2018 to cars "sold in certain cold-weather states" — 21 of them. It revises the engine and transmission software and the air-conditioning control unit, and comes with an oil change. The warranty extension is separate and is not geographically limited. It takes the powertrain warranty "from the original 5 years/60,000 miles to 6 years with unlimited mileage from the original sale date", covering "any engine components, such as camshafts, rocker arm assemblies, or spark plugs, requiring repair due to damage resulting from those concerns". Both run from the original sale date, so on a used car of this age both have almost certainly expired. What is left is the record: was the update done, and did anything need repairing under the extension?

How can you check it yourself?

Pull the dipstick and look at where the level sits and what it smells like. Oil above the full mark on a car nobody has just topped up is the sign, and petrol in the smell confirms it. Check the service history for oil changes that came earlier than the schedule — owners who noticed this often started changing it early, and that pattern is itself information.

The question to ask the shop

Was Honda's software update carried out — the one covering the engine and transmission control software and the air-conditioning control unit? Was anything repaired under the extended powertrain warranty, and if so what? Which state was this car sold and used in?