In a gas engine there is a throttle which is restricting air flow at idle and while cruising. Inside the intake manifold between the throttle and the cylinders, the pistons are trying to draw air, but when the throttle is closed, or partially closed it cannot get enough air, thus it draws a vacuum, just like putting your hand over the hose of a vacuum cleaner. The throttle is necessary because the power in a gas engine is regulated by the flow of the fuel/air mixture.

In a diesel engine there is no throttle. The cylinders are free to draw as much air as they can get whether the engine is idling or at full power. The power is regulated by the amount of fuel that is injected into the cylinder. Since there is no throttle to restrict air flow, (no hand over the vacuum cleaner hose) there is very little vacuum created.


JimF is exactly right about the single side parking lights. The Germans have their act together about common sense safety. They are required by law to light the road side of a car that is parked after dark. This is most commonly seen in small towns. The streets wind around with very little room for parking a car, or to get by one.

The Germans, for the most part, actually follow these laws if you can imagine such a thing. In Germany it is a long arduous ordeal to get a drivers license. Because of this, they do not want to lose their license, thus they obey traffic laws. An additional reason that they obey traffic laws is because that by nature, most German people are obedient and orderly.

Have a great day,