Actually its not about travelling at 2k rpms its all about how you reach those 2k rpms. Suppose there are 2 person both driving at 3k rpms.
1 of them does a tire slip every time he picks up the car in 1 st and every time he does sudden braking like moon pe jakay brake lagana
The other one just feather weights the accelerator and his car takes slow time to reach 3k rpms. Whenever he is driving he sees 3-4 cars ahead and even if he has a doubt he has to brake after a certain distance he picksup his foot from the accelerator and let the car cruise and brake with light foot.
Both of them are travelling at 3k rpms now the second will get a far better mileage.
All I can say is that you are the number 1 guy.
You can get only one thing either power or economy. To say my car is just like a donkey cart when on CNG with AC on and at times I have to push it really hard to overtake a LPG rickshaw. The result of that is good mileage these days I am doing 130km + on a 8kg fill in city traffic with AC on full time. What if I do NFS every time i drive I will get 95-100 kms and that is what most of people with same car in my city are getting. Take for example a filling of 500 rs for 8kg. If I do fast driving I will get 5rs/km and if I do slow like I am doing less than 4rs/km. If your monthly drive is around 1500 kms per month than you are saving 1500 rs per month. So decide what is better 1500 rs saving or fast driving