Fuel Getting Into Engine Oil – Learn The Cause, Effect And The Fix

Fuel Getting Into Engine Oil - Learn The Cause, Effect And The Fix
Fuel Getting Into Engine Oil - Learn The Cause, Effect And The Fix

Most importantly, fuel getting into engine oil is bad. Because, it lowers the lubricating qualities of the oil.

And, also lowers the engine oil viscosity, causing the oil to thin out, to a dangerous level.

Most importantly, this results in, additional friction between the metal surfaces, causing premature wear of engine parts.

So, fuel getting into engine oil, is a condition caused by, excess unburned fuel, entering the crankcase.

Consequently, fuel getting into engine oil, happens to all engines. But, usually not to the extent, to cause engine damage. Consequently, everywhere the oil goes, the fuel follows. As a result, causing problems, through out the whole engine.

Fuel Getting Into Engine Oil
Fuel Getting Into Engine Oil

In addition, the oil films formed, are weakened and less capable of, withstanding high engine loads.

So, When You Have, Fuel Getting Into Engine Oil, Where Does The Damage Start.

One of the early signs of this happening, is a lifter ticking noise, caused by lack of lubrication. After that, engine bearings will begin to fail, lowering oil pressure and eventually causing, engine knocking noises. And, is all caused by, fuel getting into engine oil.

Usually, the first to go are the rod bearings, as they are last ones to get oil.

Worn Connecting Rod Bearings
Worn Connecting Rod Bearings

Furthermore, as the oil is being used up and replaced by fuel, the concentration of oil additives go down. As a result, fuel is also diluting the engine oil additives. And, this includes things like rust inhibitors, detergents and dispersants. Detergents help remove sludge, that can build up in the engine, over a length of time. While, the dispersants, keep the dirt from lumping together. And, also control of carbon deposits.

So, as you can see, fuel getting into engine oil, can do engine damage. Most of these issues, can happen with antifreeze as well. But, we will talk about that one later.

Worn Out Camshaft Housing Bore
Worn Out Camshaft Housing Bore

Consequently, there actually are some ways, to reduce fuel getting into engine oil, if you know the signs.

So, Learning The Cause, Effect, And The Fix, Is Very Important. Because, That May Be All You Need, To Save Your Engine.

Cause Effect The Fix
Continued operation with stops and start. Because, the fuel doesn’t burn off completely. As a result, reduce the mileage change interval, to the strictest change interval, shown by the manufacturer.
Starting in the cold. The fuel doesn’t burn off well, because the combustion temperature is low. Wait for the engine to increase in temperature, before accelerating.
Problems in the injection system. So, the drops of fuel being injected into the chamber are big. As a result,, that leads to poor combustion. Most often, the injectors, need to be inspected.
Poor combustion. Because, the fuel isn’t burning off completely. Resulting in, fuel getting into engine oil. Above all, check that the combustion chamber and the injection system, are working properly.
Worn-out engine parts, valve guides, injectors and wear. Conditions change in the combustion chamber, meaning it is no longer optimized. Consequently, the engine, needs to be inspected.
Excessive acceleration. Excess inflow of fuel. As a result, worn injectors are possible.
Mixture of rich fuels. Excess fuel. Inspection of the, injection system.
Faulty injectors. In addition, can produce too much inflow of fuel or inadequate fuel injection. Because, it does not burn fuel as well, causing deposits. Inspection of the injection system.

Pistons With Fuel Wash Damage
Pistons With Fuel Wash Damage

So, the problem of fuel getting into engine oil, causing fuel wash, seems to have reduced in recent years. As a result, this seems to indicate that, current fuel injection systems have improved.


Above all, proper maintenance, is the most important part, of owning a vehicle. Therefore, to keep it running smoothly, your vehicle highly relies on engine oil, lube, and oil filters. Furthermore, oil helps in lubricating, cooling, and cleaning the internal engine parts. Because, with time, engine oil, becomes contaminated.

Always, keep your eyes open for, early signs of fuel getting into engine oil:

Check Oil Level
Check Oil Level
  • Firstly, check your oil level. Because, it could be low or it could be too high. Consequently, some manufacturers have actually added a new notch, above the maximum mark, as a warning sign.
  • When you remove your dipstick to check your oil, Smell it !  Does it smell like fuel ? If so, have it checked and repaired, before any damage happens.

Finally, metal-on-metal contact, is the enemy of your engine and that’s why, clean engine oil is the cure.

Thank You !