This article explains why oil ends up on spark plugs, the real dangers of driving with this issue, how to diagnose it early, and a breakdown of other small car troubles many drivers ignore until they become expensive repairs.

What Causes Oil on Spark Plugs?

Oil on spark plugs means oil is leaking into the combustion chamber or spark plug tube—something that should never happen in a healthy engine.

1. Worn Valve Cover Gasket

The simplest and most common cause.

• The valve cover gasket seals the top part of the engine.

• When it cracks or wears out (often from heat or age), oil leaks into spark plug wells.

Symptoms

• Oil around spark plug holes

• Burning-oil smell

• Misfires, especially when cold

Fix: Replace gasket. Cost in Kenya: KSh 1,500–4,000 including labour.

2. Faulty Spark Plug Tube Seals

Some engines (especially Nissans, Mazdas, and some Toyotas) have spark plug tubes sealed by rubber rings.

When these fail:

• Oil fills the plug tube

• The ignition coil gets soaked

• Misfires start

Fix: Replace tube seals. Labour is usually more than parts.

3. Worn Piston Rings (Serious Problem)

If oil is on the tip of the plug (electrode), then oil is entering the combustion chamber.

This usually means:

• Worn piston rings

• Cylinder wear

• Blow-by from high mileage

Symptoms

• Blue smoke from the exhaust

• High oil consumption

• Poor fuel economy

• Loss of power

Fix: Engine overhaul or replacement.

4. Worn Valve Seals

Valve seals prevent oil from dripping into the cylinders through the valves.

When they wear out:

• Oil burns during start-up

• A puff of blue smoke appears during morning start

• Oil fouls the spark plugs over time

Fix: Replace valve seals (mid-level repair).

5. PCV Valve Failure

A stuck PCV valve increases crankcase pressure, pushing oil into the intake and ultimately onto the spark plug.

Symptoms

• Rough idle

• Excessive fumes

• Frequent oil fouling

• Increased oil use

Fix: Replace PCV valve (usually under KSh 2,000).

Is It Safe to Drive With Oil on Spark Plugs?

No.

Oil on plugs causes:

• Frequent misfires

• Loss of acceleration

• Poor fuel economy

• Hard starts

• Possible catalytic converter damage (very expensive)

• Engine overheating

It should be repaired immediately.

How a Mechanic Diagnoses Oil on Plugs

A proper diagnosis may involve:

• Removing ignition coils

• Checking plug wells for oil

• Inspecting the electrode

• Compression test (to check piston rings)

• Leak-down test

• PCV system inspection

A good mechanic will tell whether the problem is minor or engine-level.

Other Small Car Troubles Most Kenyan Drivers Ignore—but Shouldn’t

Many small issues start cheap but become VERY expensive if ignored. Here are the most common ones:

1. Engine Mounts Starting to Wear

Worn mounts cause:

• Vibrating steering

• Rough idling in traffic

• Clunk during acceleration

Fixing early costs 3–7K. Waiting too long damages:

• Exhaust

• Driveshaft

• Gearbox mounts

2. Slight Overheating

A temperature gauge “a little above normal” is a warning.

Small causes include:

• Sticky thermostat

• Low coolant

• Weak radiator cap

• Partially blocked radiator

Overheating kills engines.

3. Dirty Throttle Body

Symptoms:

• High or fluctuating RPM

• Delayed acceleration

• Poor fuel economy

A simple cleaning solves this—KSh 1,000–2,000.

4. Failing O2 Sensor

Very common in Kenyan cars.

• Sudden high fuel consumption

• Black smoke

• Hesitation

Fix early ? Save fuel and protect your catalytic converter.

5. Bad Wheel Bearings

Drivers often ignore the humming noise.

If it breaks completely:

• The wheel can lock or come off

• Dangerous at highway speeds

Replacement: KSh 3,000–8,000.

6. Loose Heat Shields

Causes a rattling noise that many assume is harmless. But the heat shield protects:

• Fuel tank

• Exhaust

• Cabin wiring

A loose shield can tear off on the road.

7. Low ATF (Automatic Transmission Fluid)

Most ignored issue in Kenya.
Symptoms:

• Jerky shifting

• Delayed acceleration

• Harsh downshifts

Ignoring leads to gearbox replacement (100K+).

8. Check Engine Light for “Small” Issues

Even if the car is driving fine, a CEL means:

• Something is failing

• Fuel economy is worsening

• Emissions are rising

• Engine damage might be starting

Scan early. Don’t guess.

Final Thoughts

Oil on spark plugs is a high-priority issue, and while some causes are simple (gasket or tube seals), others are serious (worn rings).

The key is early diagnosis.

Small car problems—vibrations, odd noises, rough idling, fluctuating RPM—should never be ignored. They are early warning signs of bigger trouble.

At MagariPoa.com, we encourage preventive maintenance to keep your car running smoothly, safely, and affordably.