As any car, including the Volkswagen, covers the miles between tune-ups, changes occur in the engine and elsewhere. The clearances between engine parts and the adjustments in other systems of the car become slowly less efficient. Mechanical wear, high temperatures and engine vibration all play a part in causing engine performance to fall off. Loss of power becomes almost impossible for the driver to notice.
One reason why the VW engine should be tuned at periodic intervals is that a small, four-cylinder engine really can't afford to be running inefficiently. Unlike big American cars, the Volkswagen is designed to operate with a small, economical engine and give reasonable performance. However, when the engine is out of tune, it can't do either. While an American V-8, with 300-plus horsepower, can afford to have 100 of these horses sleeping, the Volkswagen can ill afford to have even 20 horsepower going to waste. When a V-8 is running on only seven cylinders, it's only a 12 percent drop. However, when one cylinder in a Volkswagen fails to produce, the drop is twice as great-25 percent.
Apart from power and efficiency considerations, there is one other major reason for giving the Volkswagen engine periodic tuning attention-money. This is one incentive that should appeal to practically everyone. An engine that is kept in perfect tune will last longer because it's running exactly the way its manufacturers intended it to. And the Volkswagenwerke are by no means going to ruin their reputation of Teutonic efficiency by recommending tuning specs which do not contribute to the maximum life of their engines. Besides lasting longer, a consistently-tuned engine will get more miles per gallon over its entire life. Tuning is not expensive, either. The most expensive component of a tune-up, new spark plugs, will pay for itself in gas mileage alone even if replaced every 10,000 miles. So there you have it: more miles per gallon, more miles per engine, and most important, more miles per dollar.