Ideal RPM range for a Diesel Sedan

What is the the ideal RPM to maintain for diesel sedan eg Verna crdi or fiesta both running on 1500 cc diesel engine.

I have been driving both and saw that any upward gear shift before 2000 rpm gets a sluggish response from engine and sometime knocking sounds. However if you take RPM to 3000 either engine noise become a roar or you see you side cars are overtaking you.

Maintain your vehicle to save environment

The shift points (gear v/s RPM or speed) are mentioned in the user manuals. That said if you upshift at a speed (or RPM) below the recommended one, you will get engine shudder or even stalling.

S = k.I^2, where S is the amount of stupidity a species possesses, I is the intelligence the species has and k is the universal constant of stupidity.

Some of the modern day diesel engines exhibit turbo lag. It is not so evident in the Fiesta but in other cars, you will feel the engine to be sluggish at lower speeds. Get to know the spool RPM of the turbo and try to keep the engine speed at that point, so that you can make use of the power instantly when you need. For example, in the older swift, turbo lag was very prominent till 2k RPM, after which the car felt like a rocket. So, if we managed to keep the engine speed around 2k RPM, you can harness the power effectively, especially while overtaking, etc.

Where there is a wheel, there is a way!

if you shift up at 2k rpm, you will end up in 1500 rpm which will be ok for normal sedate running. If you upshift at 2500 rpm, you will end up at 2000rpm which will have good pickup and ideal for highway overtaking etc. upshift at atleast 2000 rpm especially at 4th, to avoid engine knocking which can be bad for the engine life.