Q: How bad is it for the car if when I accelerate i let it go to higher rpms like 4 or 5?

Hi there:

On a four cylinder or small six cylinder engine, accelerating the engine past 4,000 RPM on a consistent basis is not a good idea. The power band on lower gears tops out around the 4,500 to 5,000 RPM range. As a motor ages, the valve guides, cylinder head hardware and other close tolerance items begin to wear out. The higher they are "wound up" by bringing up the RPM past the power band can cause these components to break. Try to shift the car between 3,500 to 4,000 on a normal basis to extend your engine’s life.

Revving the engine to 4,000 or 5,000 RPMs while accelerating won’t do any damage. That is well below the red line. Once you’ve accelerated to the desired speed, you’ll want to shift into the highest gear possibly that will still allow the engine to run smoothly without lugging. This will provide the best fuel mileage and prolong the life of the engine. Listening to the engine, you will be able to tell when it’s reached the "sweet spot" where it isn’t working to hard, but also isn’t lugging.