What is the ideal RPM to get more Fuel Efficiency

When we accelerate a vehicle, the RPM increases and during slowing down it decreases. At the same time when we lower the gear power increases (RPM increase) and when we put higher gears power decreases (RPM decreases). We have to avoid very high side of RPM that is greater than 3000 as well as lower side of RPM that is less than 1500. In a vehicle engine the crankshaft transmits engine power to the transmission and then to the wheels and the crankshaft speed is measured as RPM in the tachometer. So, depending upon the speed the ideal band of the RPM is 1500-3000 only. Most of the efficient drivers remain slightly below 3000 RPM when going on a smooth road for a long drive in top gears.

Based on above premises, driving the vehicle for fuel efficiency requires many steps to be taken to remain in this RPM range and some of them are -

1. Accelerating in fast pace and then braking is to be avoided. A smooth acceleration and slow mode braking will always help in achieving flue efficiency. The engine should not be forced to work hard.
2. In wet or rough surfaces driving with high RPM is wastage of fuel. The tires will slip and drag and load on engine will increase.
3. Gear selection as per speed is very crucial and it is to be maintained to optimise the fuel efficiency. Gears should be changed smoothly 1 to 2 and 2 to 3 and 3 to 4 and not by jumping form 1 to 4. The recommended speed from changing gear 1 to 2 is about 25 Km/hr while for top gear the speed is about 45-50 Km/hr.
4. In automatic transmission (auto gear) one need not to bother for manual gear change but here also gradual speed change is the key to fuel efficiency.
5. Do not touch or slightly push the brake with your foot as it will create drag costing load on the engine.

Many cars that are being seen on roads these days will have fuel efficiency when the RPM is around 1,500 - 2,500
This is how cars are generally designed and to suit the requirements.
If the RPM is lower than this compression loss will be high. If the RPM is higher than this there will be more friction and transmission losses.
The best RPM also depends on other matters also. Fuel type and mixture, the design incorporated for airflow, the timing of ignition and valve etc are some of the factors which will be having a role in fuel consumption.
It is always advisable to use constant speed instead of going high speed and applying sudden brakes. An average speed of around 60 KM/Hour is desirable for good efficiency of the fuel.
Too many times using gears will also consume more fuel.

There are many things that need to be kept in mind for more fuel efficiency.
1. Tyre pressure - Keeping the tires at the proper pressure saves wear and tear on the tire tread . Maintain the tyre pressure that is specified by the manufacture, this will help you meet the expected fuel mileage of your car
2. Driving at a constant speed - The more time you can spend at a steady speed, the less your engine will have to work and the more fuel you can save.
3. Check & change your Air / Fuel Filter - One filter that will have a direct impact on your gas mileage is your fuel filter. Manufacturers recommend changing your fuel filter every 10,000 to 15,000 miles. Even a tiny grain of dirt can clog injectors, leading to erratic performance and lousy gas mileage. The air filter does impact acceleration but does not impact fuel mileage.
4. Avoid traffic jams - Avoid the most traffic areas. Getting stuck in traffic happens to all of us eventually. But if you can plan a route that avoids congestion. That's because a stationary vehicle requires a lot of energy from the motor.
5. Do Servicing as & when required - Maintaining your vehicle in good condition also play a good role in getting good mileage.Always do the servicing at the correct time interval/ kilometers specified by the manufacture.

RPM is a measure of thrust given by the engine to the wheels. Generally, by pressing the accelerator it will increase. The optimal fuel efficient level of RPM for a car is considered around 2500 at a consistent speed but there are many factors which will make it to achieve that fuel efficiency at that RPM. Driving the car in appropriate gears, smooth acceleration and deceleration, servicing of car in time, proper maintenance, avoid rash driving, avoid racing or frequent braking etc are some of the factors which are to be kept in mind and should be religiously followed if fuel efficiency to be achieved.

RPM is only a resulting parameter giving the power of engine being transmitted. Fuel efficiency depends on good driving practices.

RPM is basically rotation per minute and is actually not related to the mileage of the vehicle otherwise most of the companies would have limited the rpm of the vehicle..

The best way to get good fuel efficiency is to drive the vehicle at 75% of the rated rpm.