Firstly; rev counters when fitted to small cars are often quite unnecessary.  Secondly, the good majority of standard drivers often don't understand the significance of the information a rev counter offers and thirdly, you shouldn't allow your vision to dwell on the rev counter because it doesn't tell anything which is more important than the road ahead!

A rev counter simply shows the number of revolutions an engine's crankshaft (the rotating bit which converts the reciprocating motion [in a car's case, the up and down motion of the pistons] to circular motion) is revolving per minute (RPM) - usually divided by 1000; i.e., 2 on a rev counter is telling you that your engine's crankshaft is revolving 2,000 times per minute.  Typically, petrol engines of 1000cc to 1800cc (1.0litre to 1.8litre) have an operating range between zero and 6,000 revs per minute.

The dial normally has a red line area in the higher numbers indicating that the engine (not the car) is reaching its recommended maximum safe speed; entering this red area is known as  ‘redlining'.  As a general rule it would be unnecessary to run the engine in this red area for more than a few seconds at a time, if at all.  Having said that, most modern cars have a built in  ‘rev limiter' which electronically prevents the engine from  ‘over-revving' by shutting off the power momentarily until the engine speed is lowered; and it does all that without you ever being aware it's happening!

If rev counters do have any use it is to assist you in selecting an appropriate throttle and gear setting for a particular situation; employing  ‘sustained gear changing' for instance.  Also; by matching a particular audible  ‘pitch' from the engine at a particular RPM with the speed with which things travel in your peripheral vision, it is possible to maintain a particular speed, in a particular gear, without either looking at the rev counter or speedometer - but this requires a lot of practice.

Don't get too hung-up on the rev counter but if you want to experiment with the information it gives, you can start practicing in 1st or 2nd gear in say, a 40mph zone.

Most cars are eminently capable of achieving 40mph in second gear without over-revving so, take it to 40mph in second and give a quick glance at the rev counter.  It'll typically be somewhere around the 4,000 - 4,500 rpm area on the dial.  Next, find a 50mph zone and, using 2nd gear again, take the engine to the beginning of the red line area - then note the speed you're doing in mph and try to remember the audible pitch of the engine at that speed and in that gear.

Experiment in other gears on unrestricted dual carriageways and motorways (unfortunately, 5,000 rpm in 5th gear will take you well over the speed limit) and with practice you'll get to know how to obtain the best performance from your car in any gear without fear of over-revving the engine.

"...DON'T BE AFRAID TO HEAR YOUR ENGINE"!    GKB 2013