Which Civic Model Experienced Engine Oil Dilution?
3 Answers
1.5T variant models. Dilution issue: The increased engine oil originates from gasoline used for engine power. During repeated piston movements, as piston rings are not completely sealed, engine oil may seep from the piston rings into the combustion chamber, while gasoline participating in combustion may infiltrate the engine oil. Piston rings are responsible for sealing between pistons and cylinder walls. Due to installation requirements, there is always some clearance between piston rings and pistons, leading to blow-by between piston rings and cylinders. During engine operation, small amounts of fuel vapor and liquid fuel can enter the crankcase through gaps between piston rings and cylinder walls. Gasoline and cylinder oil film: When gasoline mixes with the cylinder oil film, it becomes difficult to vaporize. During cold starts, combustion becomes even more challenging, causing this gasoline to blend with the oil film on cylinder walls and be scraped by piston rings into the crankcase. Insufficient gasoline atomization allows it to adhere to cylinder walls before flowing into the crankcase, where it cannot be promptly recovered.
My previous 2017 Civic 1.5T had the oil dilution issue. During cold winter mornings, after just a few kilometers of driving, I noticed the oil level on the dipstick kept rising. Honda later admitted this was mainly a problem with 1.5T engine models produced between 2016 and 2018, especially noticeable in northern low-temperature regions. During one dealership service visit, the technician explained it was caused by insufficient cylinder wall temperature allowing gasoline to mix with and dilute the engine oil. They performed a free ECU software upgrade for me and replaced a radiator hose. Looking back, it was quite frustrating. I'd advise owners of same-year models to regularly check their dipsticks and visit the dealership immediately if they detect a gasoline smell in the oil.
I've studied the oil dilution issue with the Civic, which stems from the L15B 1.5T engine. This problem was particularly prevalent in models produced between late 2016 and 2018, especially the CR-V and Civic. During cold starts, the fuel injectors would over-spray, allowing some gasoline to seep down the cylinder walls into the crankcase, mixing with the engine oil and causing the fluid level to rise. The most concerning aspect was that prolonged use could reduce the oil's lubricating properties, potentially leading to piston ring wear. Honda recalled nearly 130,000 vehicles in 2018, primarily addressing the issue through ECU upgrades and replacing coolant pipes. The problem was completely resolved with the introduction of a new engine in the 2019 model year.
