Tips on Buying Cars: new car break-in......., piston rings, long periods

Question
I haven't had a new car in a long time... in the manual it says "Avoid driving for long periods at constant speed, either fast or slow." What do they mean by 'long periods'??  ... 20 minutes, 40, 60 or more?  It's awfully vague.  Thanks

Answer
That's a good question.  Manufacturers don't put an exact distance or an exact length of time because it's not an exact science.  During the first 3000 miles or so, the piston rings, valves and other engine components are breaking in.  I would say the distance you drive isn't what watch but varying your speed based on time will work. Every 10  or 15 minutes will get the job done.  55mph then 50 mph then 55 mph etc. It's a bit aggravating but it will help get the engine ready for the future 100,000 or 200,000 miles.

Geoff