Engine Oil Smells Like Gas? (6 Causes and How to Fix)

Do you smell gasoline in your engine oil? This alarming smell signals serious oil dilution that allows fuel where it doesn’t belong. Left unchecked, it can lead to major engine damage.

But don’t panic. You can diagnose the root cause and take action before disaster strikes.

oil smells like gas

Possible Reasons Your Oil Smells Like Gas

An engine’s oil can become contaminated with gasoline for several reasons, some of which are far more serious than others. The following are several possible reasons for the onset of this condition.

#1 – Faulty Injectors

bad fuel injector symptoms

Properly functioning injectors atomize fuel with each pop-off. This atomization allows fuel to burn thoroughly, and in the most efficient manner possible.

However, aging injectors often fail to atomize fuel in the same manner, leading to a less than adequate burn. As a result, unburnt fuel washes past the piston rings of the affected cylinder, eventually mixing with the engine’s lubricating oil.

#2 – Ignition System Issues

An engine’s ignition system features numerous individual components, all of which work together to ignite the fuel that is delivered into an engine’s cylinders. If any of these components fail (faulty spark plugs for instance), fuel can be left unburnt within one or more cylinders.

In severe cases, this fuel will wash past a cylinder’s piston rings, at which point it will begin mixing with oil found in the sump.

Related: 6 Causes of Oil on Spark Plug Threads

#3 – Overly Rich Air/Fuel Ratio

engine running rich symptoms

In certain scenarios, one or more faulty sensors can trick an engine’s engine control module into dosing too much fuel for a given situation. This, in turn, creates a “rich” condition, under which an engine is unable to completely burn all fuel that is injected.

As a result, excess fuel is washed past an engine’s cylinder rings, where it ultimately mixes with the oil that awaits below.

#4 – Internal Engine Wear

symptoms of bad piston rings and valve seals

In rare cases, the mixing of oil and gas can come as a result of internal engine wear. When an engine’s cylinder walls or piston rings begin to exhibit excessive wear, proper combustion is impeded.

As a result, a substantial amount of fuel often goes unburnt, washing down an engine’s cylinder walls, and as a result, putting an engine at risk for accelerated bearing wear.

#5 – Infrequent Oil Changes

oil change interval

In any event, a small amount of fuel makes its way into an engine’s lubricating oil, even in absence of mechanical issues. This fuel tends to be minimal at the most and poses no true risk to an engine’s longevity.

However, a lack of regular service can cause this fuel to compound, as standard oil change intervals are skipped. Eventual fuel dilution will result, often presenting a gasoline-like odor.

#6 – Frequent Short Distance Travel

fast food drive thru

Today’s OBD-II driven vehicles are programmed to run rich at startup, eventually transitioning to a somewhat leaner air/fuel ratio as operating temperatures rise. This ensures that adequate fuel is delivered during cold operation, thereby preventing stalling and poor performance.

However, this excess fuel can eventually lead to oil dilution, if few long-distance drives are ever taken.

Diagnosing the Issue

First things first, look out for any white smoke coming from the exhaust. White smoke may indicate that fuel is entering the engine oil, which is a possible sign of a problem. Keep an eye out for the check engine light as well, as it could illuminate if there’s any malfunction with the engine components.

Keep in mind that engine misfiring can also be a sign of a problem. When your engine misfires, there is a chance that gasoline enters the crankcase, which might be the source of the oil-gas smell. Several factors could cause engine misfiring, such as damaged fuel injectors, worn-out piston rings, or a faulty oxygen sensor.

Finally, you’ll want to pay attention to your engine’s performance. If it feels like it’s struggling or has lost power, it could be a sign that there’s an issue with the oxygen sensor, or the fuel mixture is overly rich.


To keep your engine running as it should and avoid the issue of motor oil smelling like gas, there are several things you can do as part of regular maintenance.

  • Regularly check oil level and viscosity for proper lubrication
  • Monitor piston rings and fuel injectors for potential issues
  • Ensure oxygen sensor and spark plugs are functioning properly to maintain air-to-fuel ratio
  • Avoid driving short distances too often to prevent engine wear and oil dilution
  • Inspect and service crankshaft as needed to prevent excess fuel entering motor oil
  • Change your oil according to recommended mileage or time intervals. Yes, old oil can go bad.


Is Gasoline in Oil Visible?

gas in engine oil

Gasoline is not always visible when mixed with engine oil. In fact, contamination of this type is far more likely to appear as a noticeable thinning of oil. This “thinning” makes motor oil appear far more translucent than it would be otherwise.

Gasoline contaminated oil will also tend to feel quite thin to the touch. This is most evident when rubbing a small amount of contaminated oil between your thumb and index fingers. This represents a relative loss in viscosity, which can accelerate bearing wear.

Is It Safe to Drive If You Smell Gas in Your Engine Oil?

engine oil smells like fuel

In general, driving a vehicle with a detectable amount of gas in the engine oil is not advisable. Doing so poses a significant risk to engine integrity, as gas can thin oil, thereby reducing its viscosity. As such, wear to critical components, such as an engine’s bearings, can be accelerated. 

This, of course, is not to say that driving with fuel diluted oil will cause instantaneous engine failure. However, doing so poses a substantial risk, and is likely to do harm, even if such harm is not immediately evident. Therefore, it is best to avoid driving a vehicle that’s oil carries a gasoline odor.

If the affected vehicle must be driven, several precautions should be taken. First, the engine’s oil and oil filter should be changed. In doing so, an oil sample can be taken for analysis. This sample can be sent off for laboratory testing, thereby confirming any suspensions of oil dilution you might have.

In any event, the root cause of an engine’s oil dilution issues should be diagnosed and remedied at the first available opportunity. Doing so minimizes the chance of secondary issues, any of which might result from operating a vehicle in absence of pure, non-diluted oil.

If you do not feel confident tackling such repairs yourself, it is important to make an appointment with your service center of choice, as soon as possible.

Is It Normal to Smell Gas After an Oil Change?

In some cases, you might notice a slight smell of gas after an oil change. This is because a small amount of residual gasoline may mix with fresh engine oil as it’s poured into the engine.

If the smell persists for a considerable time or gets stronger, it may be a sign of an underlying issue. Keep an eye on the situation and consult a mechanic if necessary.

Will Fuel in Oil Burn Off?

Yes, trace amounts of fuel in your engine oil can burn off as the oil reaches operating temperature. However, the ability for fuel to evaporate depends on the concentration and driving conditions.

Is It Normal for Engine Oil to Smell Like Gas in Some Vehicles?

Under normal circumstances, engine oil shouldn’t smell like gas. However, short driving distances, lack of oil changes, or mechanical issues can lead to this problem.

Can Gas in Engine Oil Cause White Smoke?

Yes, gas in your engine oil can cause white smoke from your exhaust. The presence of gasoline in the oil can lead to incomplete combustion, resulting in white smoke. This smoke is a sign that your engine is burning oil mixed with fuel, which can harm your vehicle’s performance and even damage its components.

Josh Boyd


  1. Hi Josh,
    I have a 2001 Lexus ES300.
    159,OOO miles. It’s showing Check Engine and Trac Off dash warning lights. The engine oil is 1/4 in above Full mark and smells like gasoline.
    What’s likely the issue?

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