Marinucci: Timely oil change still smart investment

Although modern automotive designs have eliminated or minimized some vehicle maintenance, timely oil and filter replacement remains a critical service.

In fact, certain engine advancements have made the trusty oil/filter change more important than it ever was on older, simpler engines.

Computer-controlled valve timing — a common, contemporary system — does not tolerate neglected engine oil.

Field experience has shown that a low oil level and/or dirty, thickened oil are the most common causes of system trouble. This includes an array of potentially confusing valve timing-related trouble codes.

Service sales professionals must continue preaching the value of regular oil/filter changes using high-quality motor oil and filters.

Understanding the most-basic aspects of computer-controlled valve timing may help service sales people sell engine maintenance more easily, more often. These systems are sophisticated but grasping their fundamentals may not be that difficult.

Decades ago, the vehicle's engine control computer began tailoring air/fuel mixture and ignition timing to operating conditions. But relatively recently, engineers added valve timing control to the engine computer's duties.

Computer-controlled valve timing used to be associated with upscale vehicles and high-performance cars.

But within the last 15 years, this technology spread across a vast range of high-volume vehicles. No doubt vehicles with computer-controlled valve timing have been rolling into your service bays for years now.

OK, remember that valves allow the air/fuel mixture to flow into the engine and waste gases (exhaust) to flow out of it.

The rotating component called a camshaft operates the valves. To grossly simplify, the camshaft's "clock position" within the engine determines when the valves open and close.

Altering this clock position — based on operating conditions — changes valve timing by changing when the valves open and close. This variable valve timing improves performance and fuel economy while reducing tailpipe emissions.

For auto makers as well as motorists, this combination of benefits amounts to having your cake and eating it, too.

So, how does all this work?

An intricate device known as the camshaft controller or phaser is mounted on the camshaft. The controller/phaser contains a set of vanes.

Pushing engine oil against these vanes rotates them as well as the camshaft bolted to them. This action alters the clock position of both the vanes and the camshaft within the engine.

Continuously and precisely adjusting this clock position fine-tunes valve timing to the engine's needs.

A simple but effective analogy here may be a garden hose and a fan. Imagine a box fan sitting on the shop floor. Spraying water at the proper point on the fan makes its blades rotate.

Aiming the water spray at another point on the fan makes the blades spin in the opposite direction.

The force of the water spray is analogous to engine oil pressure. The fan blades are comparable to the vanes inside a camshaft controller/phaser.

An electrically operated valve regulates the flow of oil through the camshaft controller/phaser oil circuit. The engine computer rapidly pulses this oil-regulating valve open and closed.

Engineers often employ additional filtering to protect this pulsed oil-regulating valve from dirt and debris. So, there may be a fine-mesh screen located somewhere in the passage supplying oil to the camshaft controller/phaser.

Typically, the valve-timing components I just described are the last ones to receive lubrication from the engine's oil pump. Arguably, then, they are especially vulnerable to problems such as a low oil level or restricted oil flow.

Sludge deposits inside a poorly maintained engine may restrict oil-supply passages. But when that passage contains a filter screen, the screen itself may be the site of the restriction.

These filter screens are very fine-mesh designs — perhaps much finer than most people realize. A partially or totally clogged screen in an abused engine should not surprise anyone.

While some service personnel suggest that filter screen service on an abused engine is a breeze, the screen may be situated in a very awkward location. Accessing the screen may take a lot of time.

Removing a badly varnished and sludged-up screen also may be a bigger headache than technicians anticipated.

What is more, simply cleaning or replacing a restricted screen does not cleanse the oil supply passage itself. Contaminants could collect inside the fresh screen a second time.

Flushing out the engine's oil passages may be the only realistic shot at saving a neglected engine. (Surely, the pros and cons of the internal flush procedure are topics for another time.)

Last but not least, experience has shown that neglected motor oil may cause the oil-regulating valve to jam — possibly stick intermittently. An internal-engine flush job may rejuvenate a sticking valve.

Removing the oil-regulating valve from the engine and cleaning it separately may fix it. But like the screen service, this single step does not treat the oil-supply passage itself.

I will wrap up with the reminder that an ounce of prevention is worth a pound of cure. Regular oil/filter changes with high-quality products keep computer-controlled valve timing systems humming.

Refer to the auto maker's recommendations for service intervals and service definitions. When in doubt, change the oil and filter at shorter intervals.

Timely maintenance always has been — and still is — the cheapest insurance against premature engine trouble.