You've noticed a fuel smell from your 2019 Acura MDX's engine bay, or perhaps the oil level seems higher than where you left it. These symptoms suggest oil dilution—a condition where fuel contaminates the engine oil, reducing its lubricating properties and potentially causing engine damage.
What Is Oil Dilution?
Oil dilution occurs when unburned fuel enters the crankcase and mixes with engine oil. This diluted oil:
- Has reduced viscosity (becomes thinner)
- Provides less protection against wear
- Can cause increased engine wear
- May lead to bearing damage in severe cases
Why It Happens in the MDX
The 2019 MDX uses a direct-injection 3.5L V6. Oil dilution in these engines typically results from:
- Cold climate operation - Engine doesn't reach full operating temperature
- Short trip driving - Oil never gets hot enough to evaporate fuel
- Direct injection characteristics - Fuel spray can wash cylinder walls
- Prolonged idle time - Engine runs rich without adequate heat
How Oil Dilution Develops
Under certain conditions:
- Some fuel spray contacts cylinder walls
- Fuel washes past piston rings into the crankcase
- Without sustained high temperatures, fuel doesn't evaporate
- Fuel accumulates in the oil over time
Symptoms of Oil Dilution
Common signs include:
- Fuel smell - Oil smells like gasoline
- Rising oil level - Level increases without adding oil
- Oil appears thin - Lower viscosity than expected
- Increased oil consumption later - As diluted oil burns off
Honda/Acura Response
Honda has acknowledged oil dilution issues in some vehicles and issued software updates that:
- Modify fuel injection timing and quantity
- Adjust engine management in cold conditions
- Change transmission shift points to build heat faster
Prevention and Maintenance
- Reduce short trips - Allow engine to reach operating temperature
- Check oil regularly - Monitor level and smell
- Shorten oil change intervals - Change more frequently in cold climates
- Apply software updates - Ensure latest calibrations are installed