PCV Oil Valve Consumption

PCV Oil Valve Consumption

Automobiles must possess immaculate and efficient motors. One of the techniques employed to maintain engine cleanliness is through the process of blow-by, where dangerous emissions and oil escape from the crankcase and into the atmosphere.

A defective Positive Crankcase Ventilation (PCV) valve can cause the engine to inhale harmful discharges, resulting in carbon accumulation and substandard performance.

A faulty PCV valve can further lead to oil leaks, as the gaskets and seals rupture, compelling the engine to consume more oil to compensate for the leakage, amounting to approximately 10% of the overall oil consumption.

Read on as we delve deeper into PCV oil valve consumption and more.

What is a PCV Valve?

The acronym PCV stands for Positive Crankcase Ventilation, one of the earliest and most commonly used emission devices in numerous automobiles.

Its chief function is to eliminate crankcase emissions from the engine and convey them to the intake, where they have combusted again in another engine cycle, thereby enhancing the engine's efficiency and cleanliness.

Most PCV valves are manufactured similarly, featuring two hose connectors and a spring-loaded one-way valve inside.

During idle or low RPM, the intake manifold generates a substantial vacuum that aids in efficiently suctioning emissions from the crankcase.

However, during higher RPM and faster crankcase pressure build-up, the PCV valve opens fully and exhausts additional crankcase ventilation. The valve will also close to prevent backfiring from the crankcase.

In turbocharged engines, it is vital to prevent boost pressure from entering the crankcase, which could result in oil leaks and gasket blowouts.

To this end, a one-way PCV valve is indispensable. These valves are designed differently, operating solely during idle and low RPM.

Additionally, some PCV valves feature three connectors for vacuum, which are regulated by electric vacuum solenoids.

How Important Is the PCV Valve?

New vehicle owners may not immediately realize that a defective PVC valve left unrepaired can cause far more damage to the engine than they might imagine. If the damage is extensive, replacing the entire system may become necessary.

Apart from the common issues of oil leaks and excessive fuel consumption, the engine may bear the brunt of these problems.

While these issues are noticeable, detecting them does not mitigate the effects of dirty engine oil, which can cause further harm to the engine.

Unfortunately, many car owners only realize the need to replace their PVC valves when there is still time.

This is due to a need for more awareness regarding the importance of routinely examining the PVC system. Costly damages may result from a defective PVC valve.

Some car owners need to pay more attention to the recommendations of their mechanics regarding PVC valve replacement.

Although some car manufacturers stipulate when a vehicle's PVC valve should be replaced, car owners must pay more attention to these guidelines.

PCV Oil Valve Consumption

The PCV system of your vehicle is precisely engineered to incinerate the blow-by gases that make their way into the crankcase.

During the combustion process of gasoline in the engine's chamber, some combustion gases bypass the piston rings and infiltrate the crankcase.

In the past, older vehicles utilized draft pipes to vent such gases into the atmosphere. Due to the negative implications of releasing combustion gases into the environment, manufacturers devised a more sustainable system for reprocessing these gases.

The PCV valve has a small spring to counter high engine vacuum during cruising, deceleration, and idle. The spring prevented excessive oil vapor from being suctioned into the intake and burned.

If the spring malfunctions, the engine will produce too much oil and oil vapor, resulting in a low-oil situation. Although the spring may occasionally become obstructed and seize up, such incidents are infrequent due to sufficient lubrication from the oil vapor.

A clogged PCV valve can provoke numerous other complications. When the valve becomes obstructed, the internal crankcase pressure cannot escape, leading to potential seal or dipstick failures.

When a seal fails, it necessitates replacement, resulting in significant expenses. Additionally, it may cause an abrupt loss of substantial amounts of oil, in contrast to a PCV valve that remains open and results in slow oil consumption.

Signs That Your PCV Valve Is Going Bad

A malfunctioning PCV valve can manifest in various ways. One of the most prevalent indications is an unstable idle and poor engine performance. In addition, a warning light on the dashboard may appear, signaling a system malfunction.

Another tell-tale sign of a bad PCV valve is the excessive use of engine oil, and you might observe blue smoke emanating from the exhaust.

Below are some more specific symptoms that may indicate a faulty PCV valve:

Rough Idle

As the PCV valve governs the flow of air between the crankcase and the intake manifold, a defective PCV valve can result in identical symptoms to those of an intake air leak.

This includes excessively high idle RPM and other peculiar idle behaviors, such as a notably uneven idle.

Consequently, inspecting the PCV valve if you notice any abnormal idle issues is advisable.


A malfunctioning PCV valve can lead to an erroneous lean or rich fuel mixture, which may result in misfires during acceleration or idling.

An excessively lean fuel mixture may fail to ignite the cylinders properly, leading to misfires. Similarly, a vibrant mixture may extinguish the spark with the fuel and cause misfires.

Increased Oil Usage/Leaks

When moisture obstructs the PCV valve or hoses, the engine crankcase experiences a surge in pressure that forcefully drives the cylinders to increase the pressure, resulting in gasket breaches.

If you observe a sudden increase in oil leaks and consumption, verify the PCV valve and its hoses for blockages.

The Check Engine Light Comes On

Among the conspicuous signs of a defective PCV valve, the appearance of the check engine light on the dashboard is one of the most prevalent. When the engine light illuminates, the engine control module stores a trouble code.

To access this trouble code, an OBD2 scanner is required. It is worth noting that older cars with mechanically-controlled engines and a PCV valve may not exhibit this symptom.

A Lean/Rich Mixture

Due to the problems mentioned above, a defective PCV valve may exhibit symptoms similar to an intake leak, and the air-to-fuel ratio can be affected.

Ordinarily, the air-to-fuel mixture becomes lean, and the symptoms experienced are akin to those of a lean mixture.

A rich mixture, on the other hand, frequently results in slightly more gray or white smoke than usual emanating from the vehicle, and you can detect the odor of gasoline. A lean mixture is more challenging to identify but often leads to misfires.

Rough Acceleration

A defective PCV valve that disrupts the fuel mixture can cause acceleration to become rough at both high and low RPMs.

While a broken PCV valve typically manifests at idle RPM, in some cases, it can also affect higher RPMs depending on the valve's configuration.

Different Colors of Smoke From Exhaust (Black, Blue, and White)

If the PCV valve or its hoses become obstructed, the crankcase will generate excess pressure to force oil into the combustion chambers.

As a result, the oil will burn within the engine and escape through the exhaust pipe, producing significant amounts of blue smoke.

A faulty PCV valve can also lead to fuel mixture problems, resulting in white or black smoke from the exhaust pipe, depending on the type of mixture issue the engine is experiencing.

In summary, if you observe any unusual smoke from the exhaust pipe, you must check that the PCV valve is functioning correctly.

How Long Can You Drive With a Bad PCV Valve?

Although driving with a faulty PCV valve is possible, being fully aware of the associated risks is essential. Persisting with a defective PCV valve can increase oil consumption, potentially leading to engine damage.

The distance one can safely travel with a bad PCV valve depends on various factors, including age and condition.

Industry professionals suggest the driving range could fall within a broad spectrum of approximately 550 to 55,000 miles. Still, this range should be cautiously approached due to the possibility of engine harm.

How Much Does It Cost To Replace a PCV Valve?

The cost of replacing a PCV valve varies widely depending on the make and model of the vehicle and can range from $50 to $250.

The valve is typically affordable, costing between $20 and $50. Conversely, the labor expenses are susceptible to more significant fluctuation and can span from $30 to $200, contingent upon the locale of the valve, as well as the adeptness of the mechanic.

DIY replacements may save you money on labor, but the process can be complicated if the valve is located beneath the manifold.

Older cars tend to have easily accessible valves that can be replaced in as little as 10 minutes.

In contrast, newer models may require over three hours to replace if the valve is underneath the intake. In rare cases, the intake must be removed to access the PCV valve.

Where in the Engine Is the PCV Valve?

The PCV Valve is commonly situated atop the engine's valve cover, though it may also be found on a conduit between the valve cover and the air intake filter.

To locate the PCV valve, trail the hose that runs along the top of the engine. It's worth noting that certain automobiles possess a built-in PCV valve within the valve cover.