Can I drive with oil in my spark plugs?

Quick Answer

It is not recommended to drive with oil in your spark plugs. Oil in the spark plug wells or on the spark plugs themselves can cause misfires, rough idle, power loss and engine performance issues. The best course of action is to replace the spark plugs and address where the oil is coming from. Driving with oil fouled spark plugs risks damaging the catalytic converter and engine.

What causes oil to get on spark plugs?

There are a few common causes of oil getting on or in spark plugs:

• Worn valve guide seals – Allow oil to leak past the seal and down the valve stem into the combustion chamber
• Worn piston rings – Allow oil to get above the rings and down into the combustion chamber
• Excessive oil consumption – Either from leaks or internal engine issues that allow oil to be consumed and make its way to the spark plugs
• Incorrect spark plugs – Using a spark plug with the wrong heat range can lead to oil fouling
• Clogged PCV system – Can increase crankcase pressure and force oil past seals and rings into the combustion chamber

Figuring out where the oil is coming from is important to properly fix the issue. Replacing just the spark plugs without addressing the root cause will likely lead to continued oil fouling problems.

Effects of driving with oil fouled spark plugs

Driving with oil fouled or wet spark plugs can cause:

• Misfiring – Oil fouling prevents a good spark, leading to misfires
• Rough idle – Misfires will make the engine run rough at idle
• Power loss – Loss of combustion reduces engine power and performance
• Difficult starting – Hard to start a fouled engine as spark is weak or non-existent
• Increased emissions – Unburned fuel and oil is expelled from the exhaust
• Catalytic converter damage – Unburned fuel and oil contaminates and ruins the cat converter

Prolonged driving with oil fouled spark plugs can also cause engine damage from pre-ignition and detonation. It’s best to address oil fouled plugs promptly to avoid damaging the engine.

How to tell if spark plugs are oil fouled

Here are signs your spark plugs may be oil fouled:

• Check engine light – Oxygen sensor or misfire codes often set
• Rough idle – Engine will shudder at idle with multiple cylinder misfires
• Hard starting – Takes several cranks to get the engine running
• Power loss – Noticeable lack of power under acceleration
• Fuel smell – Fuel odor present from unburned hydrocarbons
• Black smoke – Exhaust produces black smoke from burning oil
• Remove plugs – Physically look at removed spark plugs for oil fouling

Removing the spark plugs and examining them is the surest way to diagnose oil fouling. The ceramic insulator around the center electrode will appear wet with oil, and the electrodes may be coated with oil deposits. Compare to a new spark plug to see the difference.

Can I drive short distances with oil in spark plugs?

It’s not recommended to drive even short distances with significantly oil fouled spark plugs. Misfires from oil fouled plugs put extra strain on the engine and catalytic converter. The engine may suffer damage from just a short drive.

However, mildly fouled plugs may be ok for very short trips of just a couple miles to the repair shop. But prolonged driving risks damaging expensive components. Best practice is to replace oil fouled plugs promptly before driving the vehicle.

Is it safe to drive with a little oil on spark plugs?

A small amount of oil residue or misting on the spark plugs may not cause major performance issues. But any significant oil fouling or wetness on the insulator is not safe to drive with.

Oil in the spark plug wells can also be problematic, even if the plugs themselves look ok. Oil puddling in the wells will get splashed onto the plugs as the engine runs.

For reliability and safety, it’s best to thoroughly clean any oil from the spark plugs and wells before driving. Don’t take chances with minor oil fouling.

Can I drive 100 miles with oil on spark plugs?

Driving 100 miles with oil fouled spark plugs is not recommended and risks engine damage. Misfires and power loss will be apparent within just a few miles. Prolonged driving allows unburned fuel and contamination to build up.

Engine detonation from misfiring can quickly overheat and damage pistons and catalytic converters. The savings in tow truck fees are not worth the extensive repairs caused by driving with wet spark plugs.

Is it safe to drive 5 miles with oil on spark plugs?

Driving just 5 miles with minor oil residue on the spark plugs is generally safe, provided the engine seems to be running normally. But any significant oil fouling should still be addressed before driving the vehicle.

The risks of catalytic converter and engine damage ramp up with continued driving. It’s advisable to carefully inspect and clean or replace oil fouled plugs as soon as possible, before driving more than just a mile or two.

Can you drive 100 miles on 2 bad spark plugs?

It’s generally not advisable to drive 100 miles with even just two oil fouled or bad spark plugs. Misfiring from two cylinders will put strain on the whole engine. Oil and fuel contamination can spread to the other cylinders.

Driving with multiple cylinder misfires also risks overheating and ruining the catalytic converter. The engine computer may detect misfires and go into a reduced power ‘limp mode’ to protect the engine after just a few miles. It’s best to fix misfiring spark plugs promptly.

How far can you drive with a misfire?

It’s safest not to drive more than just a few miles with any engine misfire caused by oil fouled or bad spark plugs. Engine performance will be noticeably poor right away.

Most mechanics recommend no more than 10-15 miles driving with a misfire. Engine computer safeguards will typically activate within this range to prevent damage. But it’s smartest not to rely on limp mode and to repair misfires as soon as possible.

Is it better to replace all spark plugs or just the bad one?

It’s usually recommended to replace all the spark plugs rather than just a single bad plug. As engines age, the other plugs are likely close to the end of their service life anyway. Mixing an old worn plug with a new one can cause performance issues.

Replacing all plugs ensures you have fresh properly gapped plugs that will all wear evenly. Partial plug replacement runs the risk of having to do the job again soon to replace another failing original plug. Doing all at once saves labor down the road.

How long can you drive with a spark plug misfire?

It’s inadvisable to drive more than just a mile or two with a spark plug related engine misfire. The longer a misfire persists, the greater the risks of catalytic converter failure and engine overheating or detonation.

The engine computer may activate ‘limp mode’ where power is reduced. But relying on computer safeguards is unwise. Have misfires repaired immediately to avoid being stranded when limp mode finally cuts engine power. Don’t drive through serious spark plug misfires.

Should I replace all spark plugs if one is bad?

Yes, it’s usually a good idea to replace all the spark plugs when you find one bad or oil fouled plug. If one plug has failed or worn out, there is a good chance the others are not far behind. Mixing a new plug with older worn ones can cause uneven performance.

Replacing a full set ensures all plugs are fresh and properly gapped. Partial replacement risks having to do the job again soon when the next original plug fails. Labor costs are reduced by doing a complete plug set all at once.

Can I drive with a clogged catalytic converter?

It’s not recommended to drive with a clogged catalytic converter, especially if you’ve been driving with oil fouled spark plugs. A clogged catalytic converter causes poor performance, overheating, and risks total failure of the emission control system.

Spark plug misfires allow unburned fuel and oil to reach the catalytic converter, causing the restriction. Continued driving can melt and destroy the fragile honeycomb structure inside, necessitating total cat replacement. Don’t drive long with any suspected cat converter issues.

Conclusion

In summary, driving any significant distance with oil fouled or bad spark plugs is never recommended. Engine misfires from oil contamination risk catalytic converter damage and internal engine components from detonation and overheating.

Promptly replacing wet, oil fouled plugs can prevent expensive repairs down the road. Don’t try to just drive through spark plug misfires, as the savings aren’t worth the potential repairs. Address oil leaks and seek immediate diagnosis of any engine misfire to identify and fix the root cause.