Spark plugs can tell you a lot about the health of your car’s engine. For example, you might find that the plugs are fuel soaked, indicating a fault with the fuel or ignition system, or that the plugs are carbon fouled, pointing to a rich running condition.
Or you might find that the spark plugs are wet with oil. What does this condition mean, and is it something you should be worried about?
What Is a Spark Plug?
Spark plugs are small electrical devices that convert thousands of volts of electricity into sparks meant to ignite the mixture of fuel and air inside all gasoline-burning combustion engines. This ignition leads to a controlled miniature explosion, and the energy from this is harnessed to run the engine.
Threading into the cylinder heads of engines, pressured gas and air pushed by the piston is ignited by their spark, slamming the piston back in a fraction of a second.
Exhaust pushes the piston back as more fuel and air is drawn into the cylinder, and the cycle repeats. Vehicle spark plugs rarely form any debris that prevents them from working, but spark plugs for small two-stroke engines are a different matter.
What Will Happen If There Is Oil On Spark Plugs?
With the way the combustion system is wired, air and fuel are the only two things that should come into contact with your spark plugs. When everything is in working order, there shouldn’t be any oil on your spark plugs.
If oil indeed finds its way to the spark plugs, an oil-soaked spark plug might not be able to make a spark effectively or at all, which means suboptimal or, worse, no ignition, no combustion, and no energy generation. Even if the fuel pump is supplying fuel to the chamber, the fuel will find a way to escape the cylinder without burning.
In general, an oily spark plug directly affects engine performance, and if this problem of oil on spark plug threads is prolonged enough, it can prematurely wear out the engine bearings because too much fuel is piling up in the oil pan. In addition, it can also cause permanent damage to the catalytic converter.
Is it bad to have oil on your spark plugs?
The most common cause of oil on spark plugs is a leaking valve cover gasket. Once the seals around or next to the plugs start to leak, oil can seep into the spark plug wells. You do not want this oil to get into the cylinder.
This decreases the space inside the combustion chamber, which can cause hydro locking. Once you fix the seal, remove the spark plugs and place rags over the plug wells. Crank the engine. This will push the oil out onto the rags.
Once there is no more oil coming out of the plug wells, you can reinstall the plugs.
Reasons There’s Oil On Your Spark Plugs
Once you’ve discovered oil on your spark plugs, it’s time to dive into why it’s there. It’s not like there’s a spark plug gasket that’s leaking – so what’s going on? We’ve highlighted the most common reasons there might be oil on your spark plugs below.
#1. Leaky O-Ring Seal.
While your spark plugs might not have a gasket, they do use O-rings. These O-rings keep oil and everything else on one side of the spark plug, and the other side remains dry.
If you only have oil on one spark plug, you might have a leaky O-ring seal. This is one of the best outcomes if you have oil on your spark plugs. However, you still need to address the problem as soon as possible. Leaky O-ring seals can cause your engine to misfire and lead to more extensive damages.
#2. Blown Head Gasket.
While coolant in your compression chamber is what most people associate with a blown head gasket, another fluid that could be leaking is oil. When that happens, it’s common for oil to get into the combustion chamber.
You’ll notice excessive smoke, oil in your coolant reservoir, and there will be some oil on the tip of your spark plugs. You’ll need to replace the head gasket before the problem worsens and leads to more severe concerns. The good news is that head gaskets are cheap – the bad news is that it’s a labour-intensive process.
#3. Worn/Leaking Valve Guides.
Valve guides ensure that your intake and exhaust valves stay in the appropriate position at all times. Not only that, but they have seals that keep oil out of the combustion chamber.
If those seals give out, then oil gets into the combustion chamber, and it’s a quick hop, skip, and jump away from getting on the spark plug gaskets.
Like other components here, valve guides themselves aren’t that expensive, but they require a lot of work and time to replace – which can rack up a massive bill at the repair shop.
#4. Valve Cover Gasket Leaking.
Your vehicle uses valve cover gaskets to keep oil near components that need it and away from those that don’t. One of the components it keeps oil away from are the spark plugs. But if the valve cover gasket is leaking, then oil can easily seep into the spark plugs.
Like head gaskets, valve cover gaskets are cheap but it’s a labour-intensive process to replace them.
#5. Damaged Piston Compression Rings.
Around each piston in your engine, there are compression rings that keep oil from seeping into the combustion chamber. But when these compression rings are damaged, nothing is keeping the oil from seeping into the combustion chamber.
These rings keep everything running smoothly and prevent more significant problems. So, if you suspect damaged compression rings, it’s best to repair them as soon as possible.
#6. Damaged Piston.
While damaged or cracked pistons are rare, it’s not entirely unheard of. Combustion chambers get extremely hot, and as the pistons age, this heat can become too much for them. If you have a cracked piston, you’ll need an engine rebuild, which is not a cheap process.
However, if you let the problem go, you risk breaking down on the side of the road and potentially completely destroying your engine. Cracked or damaged pistons isn’t a problem you can ignore.
Oil in the Spark Plug Well Symptoms
The number of symptoms indicate that there is oil in your vehicle’s spark plug well. With these common signs, you can easily detect and resolve such a problem before the car develops further issues.
These signs are useful when determining how to remove oil from the spark plug well. Some of the most common symptoms of oil in spark plug wells are as follows:
1. The Smell of Gas Emanating from the Tailpipe
Have you ever wondered why you keep smelling gas coming from the exhaust pipe of your car? This could indicate that there is oil in your Toyota Camry’s spark plug well. This is true for many other vehicles, and in some cases, the odour penetrates the car cabinet.
2. Blue Exhaust Smoke
The exhaust pipe may soon begin to emit blue smoke, indicating that oil is being burned somewhere in the engine. Typically, such indicators appear when there is oil in the spark plug well.
When there is oil on the spark plug, it affects the engine’s efficiency and how it burns fuel. The fuel supply increases as the ECU attempts to adjust the fuel ratio. Regardless, unburned excess fuel in the combustion chamber would pass through the exhaust valve.
3. Reduced Engine Performance
As the oil in the spark plug well makes contact with the plug, spark generation is reduced. Remember that this spark is in charge of the car’s ignition. The oil contamination of the spark plug tip would be disastrous.
In essence, the fuel/air mixture would have fewer chances of igniting in the combustion chamber of the vehicle. There will be insufficient pressure for the engine to function properly if there is no proper combustion.
4. Engine Misfiring
Engine misfiring can occur in any of the engine’s cylinders due to incomplete fuel/air mixture combustion.
With oil in the spark plug well, the plug is less likely to generate enough spark to complete the ignition of the gas/air mixture. As a result, you will begin to notice misfiring in your vehicle’s engine.
5. Increased Fuel Consumption
An increase in fuel consumption indicates that the spark plug is being clogged by oil. In essence, if you notice an increase in fuel consumption, inspect the spark plug to see if it has any oil on it. This sign will show you how to drain the oil from the spark plug well.
6. Engine Backfiring
This occurs when the fuel/air mixture combusts outside the combustion chamber of the engine cylinder.
When there is oil in the spark plug well, this symptom appears. It is caused by improper combustion of the fuel particles, which causes them to migrate to the exhaust.
How to Get Oil Out of Spark Plug Wells
If there’s oil in the spark plug wells, you might be wondering what you need to do to get it out. The truth is that it’s more important to find the source of the problem and fix it.
That’s because the oil will work its way into the compression chamber and burn off. As long as there’s no more oil leaking in, that’s the end of your problem.
So, while oil on your spark plugs is a big deal – it’s not something you need to tear your engine apart to clean. Once you’ve found and repaired the faulty component, you should be good to go.
However, if you are worried about the excess oil, all you need to do is spray some carb cleaner into the spark plug holes and let the oil run into the combustion chamber. Reinstall the spark plugs and let your engine burn off the excessive oil.
How to Fix: Oil On Spark Plugs
While simply cleaning off excess oil temporarily solves the fouled plug problem, pinpointing and repairing the root cause of the oil leak is necessary or you’ll just be repeating the same cleanup process.
Potential solutions include:
- Replace damaged or worn spark plug tube seals and O-rings allowing engine oil down into the well. Ensure the fresh seals are properly fitted.
- If oil smoke or coolant mixing suggests head gasket failure, replace the complete gasket set to prevent further compression leaks. This extensive engine repair restores the seal between the block and heads.
- For oil-fouled plugs alongside valve train noise, consider replacing worn valve stem seals and guides that have loose tolerances. This also necessitates some valve and cylinder head removal for access.
- Confirm piston, ring and cylinder wall wear as potential sources of oil blow-by internally in the engine, especially on high mileage vehicles. Engine overhaul and rebuild may be required in such cases.
While fouled spark plug replacement and wiring insulation cleaning may get a rough-running engine operational short term, the root sources listed above must get addressed to prevent ongoing oil contamination issues leading to misfire conditions or catalytic converter damage.
What Are the Negative Effects of Oil on a Spark Plug?
If your spark plug is coated in oil, your engine will malfunction in one of three ways:
- Complete failure to start;
- Difficulty starting;
- Rough running.
Can You Drive With Oil On Your Spark Plugs?
In short, yes, you can drive with oil on your spark plugs, but you’re going to want to figure out how it got there. That’s because oil on your spark plugs isn’t a normal condition, and it can be indictive a much more serious problem.
The oil on the spark plugs isn’t the problem – it’s how the oil got there that can damage your engine.
Can you Clean and Reuse Spark Plugs?
Absolutely! Once you’ve completed the necessary repairs to keep the oil from coming back, use a carb cleaner to spray down the electrode and threads and let everything dry. Once it’s dry, reinstall the spark plugs, and you’re good to go!