Why, with electronics controlling almost everything on today’s vehicles and longer and longer recommended maintenance and service intervals for most engine components, is your mechanic saying your car needs a tune-up? Do you really need a tune-up, and will it bring real benefits?

Tests show that installing premium spark plugs, improve fuel mileage by as much as 4.8% over originally installed original equipment plugs.

“If your fuel mileage has gone to pot, if your car or truck is sluggish and appears to have lost its zip, if it is hard to start, or you have failed an emission inspection, you almost certainly need a tune-up. These are sure signs something is amiss under the hood, and you can expect a good tune-up to improve your vehicle’s gasoline mileage, restore the performance and pleasure to your driving, make sure you pass that emissions inspection, and possibly save your catalytic converter from costly replacement,” according to Martin Kashnowski, Director of Product Management, Consumer Products for Robert Bosch Corporation.

“A tune-up in the good old days meant routine replacement of spark plugs, distributor points, rotor, condenser, distributor cap, spark plug wires, PCV valve, and air and fuel filters. But the evolution of electronics has eliminated most of those components in favor of sophisticated devices that don’t necessarily need periodic replacement. But they do, however, need to be inspected and replaced as necessary, especially when there’s some sort of performance problem,” said Kashnowski.

Basically, a tune-up today usually means:

Inspect and replace the spark plugs

Check and replace the spark plug wires

Replace oxygen sensors if mileage or driving patterns warrant

Check and replace the distributor cap and rotor (if so equipped) if worn

or cracked

Inspect and replace air and fuel filters as needed

Verify proper operation of various sensors and other electronic control devices

But isn’t everything under the hood supposed to last for 50,000 miles or more before replacement is needed? Well, maybe yes and maybe no. Many components today have a recommended replacement interval of 50,000 miles or more under ideal operating conditions – the problem is, few of us drive under ideal operating conditions.

‘Normal driving’ can punish vehicles

“Short trip driving, loading up the engine by carrying or pulling excess weight for extended periods, or constant idling can prevent the spark plugs from getting hot enough to burn off deposits, causing them to foul, for instance. If the vehicle is burning oil due to worn valve guides, seals or piston rings, this will also foul spark plugs – as can cracked or deteriorated plug wires,” Kashnowski noted.

Fresh, premium spark plugs use multiple paths to generate a strong, consistent spark.

“Fouled plugs, or plugs whose electrodes are so worn they widen the air gap so much the plug will not fire properly mean the engine is operating at less than peak efficiency, and may actually be misfiring on one or more cylinders.

This will clobber your gas mileage and decrease performance noticeably, and a single fouled spark plug can cause your car or truck to fail an emissions test,” he continued.

“If your vehicle has bad or worn plugs, it’s performance and efficiency will only get worse as the miles roll by.

No matter how many miles are on them, your mechanic should replace the spark plugs if they’re oil or carbon-fouled, if they’re covered with deposits, or if the electrode is noticeably worn.”

When replacing spark plugs, consider the real advantages of upgrading to premium spark plugs.

These plugs, such as Bosch Platinum2 or Platinum+4 premium plugs, feature a pure platinum center electrode that reaches operating temperature faster, ensuring the plug will not build up carbon deposits. “

A platinum center electrode, combined with two or four side (ground) electrodes resists wear, corrosion – and they resist erosion.

Every time a spark plug fires, metal is lost in the process, and over time this widens the firing gap, which puts extra load on the electrical system, saps performance, and may eventually lead to misfire,” he emphasized.

Ignition wires

should be sound

While replacing the plugs, your mechanic should also check the ignition wires, which carry the “juice” from the coil and distributor to each spark plug (some modern cars use distributorless ignition and direct coil packs for each cylinder that eliminate the need for spark plug wires). Ignition wires must be sound in order for the spark plugs to fire correctly, and wires deteriorate with age, mishandling, heat and vibration – any condition that increases internal resistance or prevents proper voltage from reaching the plugs will cause misfires.

Modern wires have a conductive core of carbon-impregnated fiber, copper wire (mostly European vehicles), or spiral-wound nickel alloy wire (known as Mag wire) encased in insulation and an outer protective jacket.

“If your mechanic recommends replacing the ignition wires, low-resistance Mag core wires are available for most applications and a good bet to ensure strong spark and long life. They will provide your spark plugs with maximum voltage for years to come,” according to Chuck Ruth, Director of Product Management, Engine Management Systems, for Bosch.

Be careful. Some vehicle manufacturers recommend replacing the coil whenever replacing ignition wires, to avoid the higher resistance in new wires from damaging the ignition module.

Oxygen sensors control fuel mixture

Another critical component in keeping today’s vehicles running properly is the oxygen sensor.

“In all modern cars, SUVs and light trucks, oxygen sensors located in the exhaust system monitor the unburned hydrocarbons and oxygen in the exhaust and send signals to the engine’s computer, which uses this information to maintain the proper mixture of fuel and air fed to the engine.

These O2 sensors are normally located in the exhaust system before the catalytic converter to measure exhaust emissions as they come from the engine combustion chambers. Some vehicles also install additional O2 sensors after the catalytic converter, comparing the signals before and after the converter to make sure the converter is operating properly,” said Ruth..

Oxygen sensors can become sluggish and less sensitive as they age, and a worn or defective O2 sensor is often the main cause of failure to pass an emissions test – and will likely cause your fuel mileage to drop significantly, and can sap its performance.

It may also cause a “Check Engine” light to come on. Testing the oxygen sensors according to the vehicle manufacturer’s service procedures, and replacing a sluggish or defective O2 sensor can improve fuel economy from 10% to 15% and pay for itself in a year in fuel savings alone, while restoring your vehicle’s emissions to proper levels. Also, it can reduce the chances of an overly rich fuel mixture damaging your catalytic converter.

“Obviously, O2 sensors should be replaced if they have failed or are clearly malfunctioning. But to maintain vehicle efficiency and performance, we recommend replacing these sensors regardless of their condition at certain ‘safe’ intervals:

Replace unheated O2 sensors (on 1976 to early 1990 vehicles) every 30,000 to 60,000 miles

Replace first generation O2 sensors (mid-1980 to mid-1990 vehicles) every 60,000 miles

Replace second generation O2 sensors (mid-1990 to current vehicles) every 100,000 miles

“The same hard driving patterns that wear out spark plugs early, also take their toll on oxygen sensors. If your ‘normal driving’ is punishing your car or truck, don’t be surprised if your mechanic tells you he needs to replace one or more oxygen sensors,” Ruth said.

Distributor cap, rotor – and filters – essential

Ignition components such as the distributor rotor and distributor cap, which direct the flow of electricity to the spark plugs, must work properly if the spark plugs are to fire when they are supposed to — or fire at all. The rotor inside the distributo

r and under the distributor cap sends high voltage to each spark plug as it spins and brushes past individual contacts in the distributor cap.

Corrosion or oxidation build-up, moisture, carbon tracking on the rotor or inside the cap can cause weak ignition. Cracks or burn-through in the distributor cap can cause spark plug misfiring, or no firing at all.

If in doubt, replacing the distributor cap and rotor is simple and inexpensive insurance against poor performance and fuel economy – and potential engine failure, when you least expect it.

Replacing the air filter and crankcase breather filters is a normal part of any tune-up, and of course, tests should be conducted on all electronic control devices and sensors to make sure they are operating properly.

Worth It?

So you have spent a few hard-earned bucks on the tune-up your mechanic insists you needed.

Can you now beat everybody at “leaving the stoplight quickly,” and will you have to empty your gas tank every week or two because you’re saving so much in fuel usage? Was it worth it?

“Only time will tell whether you will be aware of all the improvements – but every day your car or truck starts easily, accelerates smoothly to highway speeds, uses significantly less fuel – and is in compliance with emissions requirements – you will be reaping the benefits.

“You will be seeing these benefits in dollars and cents as well as driving pleasure for tens of thousand of miles,” Kashnowski concluded.

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