9 Reasons for Generator Burning Oil (How to Fix it)

generator burning too much oil

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It is normal for generators to consume motor oil as it runs. But needing to add oil every other day because your generator is using a lot more oil than it should is a clear indication of a problem.

So, why is my generator burning oil so fast?

There are many reasons your generator may be using oil so fast, and the most common causes include

  1. There is too much oil in the engine
  2. You’re using the wrong grade of oil
  3. The air filter is either dirty or clogged
  4. The oil fill cap is loose or damaged
  5. The unit is running very hot
  6. The motor oil used is of poor quality
  7. The generator is old
  8. The seals and gaskets are worn out
  9. The piston rings are misaligned

As the engine burns off more oil, it hinders the engine’s normal function. Worse, as the oil level drops, the level of protection inside the engine reduces, which accelerates the rate of wear and tear inside the engine.

In this guide, we’ll take a detailed look at the most common causes of high generator oil consumption and know how to fix them.

9 Reasons your Generator is Using Too Much Oil

Too much oil in the engineAn increase in oil pressure forces the oil up to the combustion chamber, which burns the oilDrain the excess oil
Wrong grade of oilUsing lower viscosity of oil in the wrong season will make the oil seep up between the piston and cylinder wall and burn the oilUse an appropriate grade of motor oil depending on the season
Air filter dirty or cloggedA clogged air filter creates a vacuum that pulls in the oil from the crankcase into the combustion chamber, increasing oil consumptionClean the air filter regularly and replace it when needed
Oil fill cap is looseMoving oil inside a running generator can leak out from a loose oil cap and burn as it touches the hot engineFasten the oil fill cap or dipstick properly. Replace the dipstick if the gasket or the dipstick is damaged
Generator running hotAs the engine runs very hot it breaks down the oil which in turn increases the oil useUse a generator tent and never run the unit at high load for long periods
Poor quality motor oilLow-quality oil doesn’t break down easily, reducing overall protection and increasing oil consumptionUse high-quality motor oil from the top brand’s
Generator is oldOld generators have worn out engines that have larger gaps between the piston and cylinder wall that allows the oil an easy route to the combustion chamberReplace the engine or better buy a new inverter generator
Worn out seals and gasketsWeak or broken-down seals and gaskets allow motor oil to leak. As the leaked oil comes in contact with the engine, it burnsReplace the worn-out seals and gaskets
Misaligned piston ringsMisaligned piston rings provide an easy passage for motor oil from the crankcase to reach the combustion chamberTake it to an engine repair shop and realign the piston rings

Why is my Generator Burning Oil? (9 Reasons & Fix)

The reason behind excessive engine oil consumption can be as simple as too much oil in the crankcase to a more complex problem like a worn-out engine. Some causes are easy to fix, whereas others may require professional assistance and money.

However, a generator using too much oil is one problem you shouldn’t ignore. Low oil in a generator’s engine can have serious consequences on a generator’s overall working life.

Here are the 9 most common causes for generator burning oil and what to do about it.

1. Too Much Oil in the Engine

The #1 and the most common reason most camping generators burn oil is that you’ve overfilled the engine oil. When there is too much oil in the generator, the oil pressure inside the engine increases, forcing the oil to find ways to escape.

The increased oil pressure forces the oil out through any weak gasket or up into the combustion chamber, where it burns. Moreover, any oil that is leaking through the gaskets will also burn off as it comes in contact with the hot engine.

The most obvious cause of excessive motor oil in your generator is from the topping of oil with a generator sitting on an uneven surface. In small generators where the fill cap is not easily accessible, you may be forced to tilt the generator to an angle (45 degrees) to pour in oil easily. The uneven surface or the tilt angle can put off the oil level, making you overfill the crankcase.

The easiest way to determine if your engine has too much oil is to open the engine dipstick and check the oil level. Additionally, blue smoke from your generator’s exhaust is another common indication you have excessive oil in your generator.

If your generator shows symptoms of excess oil, you need to correct the problem by draining the excess oil to prevent oil from burning and causing damage to your generator.

Excess motor oil in a generator will not only increase oil consumption but will also cause other mechanical problems. To fix excess oil-related issues, you need to drain the extra oil from your generator’s crankcase.

To drain oil from your generator, locate the drain plug under your generator and drain the appropriate amount of oil in a container. I would suggest draining all the oil and topping it off with a new batch, as draining the right amount can be difficult.

Read More: How Much Oil does a Generator Take?

2. Using the Wrong Oil Grade

Depending on the weather, generators need to run a specific grade of oil to ensure proper functionality. Using the wrong weight of oil can cause a lot of problems including increased oil consumption.

Using a lower weight oil when the outside temperature calls for a higher weight oil means your oil will find its way up to the combustion chamber. As the oil reaches the combustion chamber, it will burn off with the fuel during the combustion process.

Moreover, generators switching from regular motor oil to synthetics may find themselves burning off a lot more oil than usual. Synthetic oil is sleeker than regular oil which makes it easy for the oil to climb up the combustion chamber.

The most obvious sign that you’re using a lower viscosity oil is oil spots under your generator. Using the wrong grade oil will not only burn oil but will also pose other mechanical problems that can create a dent in your wallet.

To prevent the wrong viscosity of oil from burning and causing other problems, you need to drain the old oil and put the right grade oil. As a general rule of thumb, you need a thicker grade oil like 10W30 during summer and a thinner oil like 5W30 during winter to ensure peak performance.

Always refer to your generator’s user manual to find out the recommended type and grade of oil for your specific model.

Read More: Can I Use 5W30 Instead of 10W30 in my Generator?

3. Dirty or Clogged Air Filter

A dirty or clogged air filter is another common cause your generator is burning or consuming more oil than usual. A generator’s engine needs clean air to function, and the air filter is responsible for cleaning the air.

However, over time the air filter collects dirt from the air which may restrict the airflow or prevent it completely. During a combustion cycle, an engine creates a vacuum that pulls in air and fuel in the combustion chamber.

But with the air filter clogged, the vacuum that is created pulls the engine oil lubricating the cylinder walls into the combustion chamber. Once into the combustion chamber, the oil mixes with fuel and burns off which increases your overall oil consumption.

To determine if a clogged air filter is causing your generator to burn oil is look for symptoms like strange engine noise, misfires, reduced fuel efficiency, etc. 

To fix this problem, simply clean your generator’s air filter or change it if it is badly broken down.

4. Loose Oil Filler Cap

Though less common, a loose or worn-out oil fill cap or dipstick can be a reason your generator is losing or consuming more oil than it should. As the generator runs, the moving piston and crankshaft move the oil vigorously.

With a loose or worn-out oil fill cap, the oil leaks out of the engine and burns as it touches the hot engine. Visually inspect the dipstick to check if a faulty dipstick is a reason your generator is burning more oil. 

You need to replace the dipstick with a new one if the gasket on the dipstick or the dipstick itself looks broken down. Moreover, fasten your dipstick properly after checking the oil level or changing the oil to prevent oil from leaking out through it.

5. Your Generator is Overheating

An overheating generator can pose a lot of problems to the unit itself while also increasing oil consumption. From outside temperature to a high electrical load, there are many reasons why your generator might be overheating.

An increase in the engine temperature increases the oil temperature inside the generator. A rise in oil temperature accelerates the breakdown of the engine oil, which in turn helps burn more oil.

To prevent your generator from overheating and burning the oil, make sure not to run the unit at its maximum load. Moreover, use a generator tent, like the GenTent when using your generator under the hot summer sun.

6. Poor Quality Oil

With time and use, the motor oil inside a generator breaks down and loses its quality, increasing the oil consumption. As the oil degrades, it loses its ability to adequately lubricate the internal moving parts of the engine, increasing friction and heat.

The added heat that is produced inside the engine accelerates the oil consumption rate while increasing wear and tear. There are a few things you can do to prevent excessive oil consumption caused by oil quality.

Firstly, make sure you check the condition of your generator oil regularly. A good rule of thumb is to check it every morning before you start using your generator. Remove the dipstick of your generator to check the level and color of the oil.

If the color of your motor oil is dark brown or black, you need to change the oil as soon as possible. Changing a portable generator oil is as simple as unscrewing the drain plug, and the oil will drain out.

Secondly, make sure to use a higher quality motor oil from top brands. Going with less popular brands just to save a few bucks may lead to increased oil consumption or worse, expensive repairs.

7. The Engine is Old

A combustion engine wears down with age creating many problems, including increased oil consumption. As a generator’s engine ages, the gap between the piston and cylinder walls increases, making it easy for the oil from the crankcase to reach the combustion chamber.

As the oil reaches the combustion chamber, it mixes with the fuel and burns. As such you may notice a high oil consumption on a unit that has a few 100 hours of runtime under its belt compared to newer generators.

To prevent a generator from consuming excessive oil as the unit ages are far from straightforward. You either need to replace the aged engine or bore out the cylinder wall and replace it with an appropriate size piston.

To me, both the fixes sound troublesome and most importantly, expensive. Instead, I would suggest you buy a new inverter generator as changing the engine will cost about the same as a new unit.

8. Worn Out Seal & Gasket 

One of the first things that wear out easily as the generator ages are its seals and gaskets. As the seals and gaskets around the engine break down, it increases the possibility of engine oil leaks.

When the engine oil leaks from in or around the generator’s engine, the leaked oil burns as it comes in contact with the hot engine. Over time, these damaged seals leak more, increasing the oil-burning ratio.

The most obvious signs of oil leaks caused by worn-out gaskets are oil stains on the engine and ground. Moreover, as the oil burns when it comes in contact with the hot engine, it produces grey or white smoke from the engine.

To correct this problem you need to take your generator to a service center and replace the worn-out gaskets.

9. Misaligned Piston Rings

A generator’s pistons are fitted with multiple metal rings that are not a complete circle but have a small gap. The gaps are mainly there to allow the rings to contract and expand depending on the temperature.

Over time, the gap on the rings may align right on top of each other, allowing the oil from the crankcase to reach the combustion chamber. As the oil reaches the combustion chamber, it burns, increasing oil consumption.

To correct this problem, you need to remove the piston and install the rings in a way that gaps are not in line with each other. This will restrict the oil from reaching the combustion chamber and limit the oil from burning.

What are the Common Signs of Generator Burning Oil?

By now you are well aware of the most common cause why your generator is burning oil. Though these are not the only reasons your generator is consuming more oil, but are the most common in portable generators.

However, there are signs and symptoms you can look for to determine if your generator is using excessive motor oil.

Some of the most common signs include

  1. Blue smoke from the exhaust
  2. Grey or black smoke from the engine
  3. Oil stains on the engine and ground
  4. Frequent low oil shutdown
  5. Your generator performs poorly
  6. Increased fuel consumption

A generator burning excessive oil is a sign of a bigger problem that is waiting to unfold if not addressed on time. Make sure to check for these symptoms and run scheduled maintenance on your generator to extend its working life.

Frequently Asked Questions

How Fast do Generators Burn Oil?

Though it is normal for a generator to burn some oil while in operation, the rate of oil burns depends on the brand and type of generator. Moreover, your generator may burn more oil than it should because of the causes we spoke about above.

What Happens if A Generator Runs Out of Oil?

The primary function of motor oil is to lubricate the internal parts of the engine and keep it protected. However, a drop in oil level inside the engine decreases the level of engine protection.

As a result, running a generator with low oil or below the recommended level can cause serious damage to the engine’s internal parts. Running a generator for a considerable amount of time with a low oil level can damage the engine beyond repair.

Most modern portable generators come with a low oil shutdown down feature that prevents the unit from running if low oil is detected. However, you need to manually check the oil level regularly if your unit doesn’t come with this feature.


A generator burning oil during operation is normal, but an excessive amount of oil consumption is an indication of a bigger problem. As the oil level drops, the level of protection inside the engine falls.

This increases the wear and tear on the engine’s internal parts, shortening the engine’s life. Your generator may burn oil for a wide variety of reasons but the ones we spoke about above are the most common.

Make sure to address the problem immediately once you identify why your generator is burning oil.