It is in fact true that driving at slightly (primal word) higher rpms is much better (for both fuel efficiency and engine life. The rpm range for the ii can be different).

Role 1. Engine life:

Every engine has a least resonant rpm. This is when your engine vibrates the least (Think of this as the contrary of that point when your entire car begins to milkshake violently due to excess load). Since the vibration is minimum at this rpm, the article of clothing and tear in the engine is minimized and so is the friction between engine components. This naturally means you take parts that run smoother and longer. This can also increase your fuel efficiency since frictional power loss is minimized.

Part two.Optimal fuel efficiency:

This rpm range need not be the aforementioned equally that for optimal engine life. Your fuel efficiency is best when y'all are not over working the car. This has multiple dimensions to it. Ideally, driving the car at a high gear, just shy of the midway mark on your tachometer is when the fuel efficiency is the maximum (i.eastward. when yous are cruising) but if y'all need acceleration yous will burn down a lot of fuel to get very little. This blazon of driving is best for the highway. In the city limits, it would be best to raise the engine to the sweet-spot (where the resonance is the least) and then shift to drop the rpm dorsum down, all the while not existence ambitious with the pedal.

Low rpms give you better efficiency for two reasons,

1. Dynamic friction is proportional to speed. (College the speed, greater the friction). This applies everywhere, from the creepo shaft to the piston-cylinder to the gearbox. A auto can rev only then much because afterward a certain betoken, the power generated is less than that needed to overcome the frictional force.

Lesser line: Lower the speed, meliorate the efficiency.

2. Volumetric efficiency. (Higher the speed, lower the volumetric efficiency) At depression engine speeds, as the engine goes through the exhaust stroke and the suction stroke, air can easily exit and fill the engine cylinder. As the engine rpm increase it becomes harder and harder for the burnt air fuel mixture to exit the cylinder (in the exhaust stroke) and for the fresh air to enter the cylinder (in the suction stroke). This translates to wastage of power considering the engine has to utilize some of the power generated to push the air out faster and faster. On the suction stroke, the air does not travel fast enough to fill the cylinder in the curt duration that the intake valve is open up. (To make matters worse, the ECU measures the pressure at the inlet and expects a sure corporeality of air to enter the engine and adjusts the fuel injected accordingly, but when the expected amount of air does not enter the engine, the fuel that would otherwise have been burnt gets wasted.)

Bottom Line: Lower the speed, better the efficiency.

Now, remember the least resonance rpm? Remember how coming closer and closer to that rpm, reduces frictional loses? This is around one-half way through your rev range. Hence you volition go the best fuel efficiency when you are in the proximity of least resonance simply low plenty to take advantage of points ane and ii. For easier understanding, look at this graph:

The higher up graph is for an engine on a test bed. For an engine on a machine, the lowest point is a little to the left at effectually 2500 rpm (but similar you stated).

Screw the explanation, give me the respond:

For best fuel efficiency:

When driving on the highway, bulldoze just shy of the midway mark. In the metropolis, rev all the way up to the sweetness-spot and and so shift up to comeback to just shy of the mid style mark.

For all-time engine life:

Do what y'all must to stay at the sweetness spot.

How to observe the sweet spot:

1.Park the machine (handbrake is engaged)

2.Offset the engine, put it in second or 3rd gear.

three.While keeping the clutch depressed, enhance the engine in steps of about 250rpm (Smaller steps if y'all are really particular).

four.At a very exact rpm, the automobile will experience like it is running smoother than usual.

v.Congratulations. You lot accept found the "sweet-spot".

          (PS. This is harder than it sounds, but I encourage you to do it!)  (Disclaimer: Sweet-spot is non a universally understood term,  when searching online or talking to your auto buddies, use the term  "Signal of least resonance".)