Safe your fuel!
I've found and prooved an idea to save your car's fuel. The idea relies on a very simple concept: the air feels cooler when the wind is moving, so I will make the wind move. What we do really needs is the feel that the car is cool, not the real temperature inside the car. So instead of reducing the temperature of output air from the air conditioner grill, I experiment by increasing the airflow. Most people tries to lower the temperature of air output from the aircond (max the compressor) and reduces the air cond's blower speed to minimum (speed 1, they afraid the blower's noise). This will stress and put your aircond compressor to work hard.
I tried the different approach by putting the fan speed to 2 and reducing the aircond compressor work to half.
The air blower in air conditioning units consumes only small amount of power (around 250w, CMIIW), while the compressor consumes way more power than the air blower (around 5Kw (5000w), CMIIW). By making the compressor works at half of its capacity and making the air blows faster, I can manage to get my car as comfortable as by setting the air temperature as low as possible and fan at minimum. Well at least thats on average tropical sun here in Jakarta, thats enough to stop me from sweating. When the day gets really hot, I usually set the air blower at 3 and the compressor at 3/4, and that really cools my car! On my car, 2008 Toyota Vios, this method grants me 9.8% in fuel reduction. The mileage increases from 13.2 km per litre to 14.5 km per litre. That's the first advantage.
How about the noise from the airconditioning system? Well nothing to worry about, the noise from aircond at speed 2 is much lower than the road noise.
When the car is parked in your quiet neighbourhood, you will hear the hiss. Nothing is too loud here, its just a noise which is as loud as your home's airconditioning system and you can still sleep when your house's airconditioning is on right?
While driving at quiet street below 20km/h, the noise from your tyre and engine will be about as loud. So, nothing to worry about.
At speed of 50km/h, you will not hear the noise from your aircond unless you are listening and looking to it.
At speed faster than 60km/h, there will be no way to hear the wind noise from your aircond.
This method will also prolong the life of your air conditioner compressor (usually they died after 6 years of use), and the aircond compressor is costly compared to the blower fan. Thats the second advantage.
So, happy saving your fuel!
To reduce your car's fuel consumption even further, you can try to lower the viscosity of your oil. My Toyota Vios now runs on Mobil 1 5W-20 oil. The car's manual specify the engine requires 5W-30 as the thinnest motor oil suitable and I usually put 10W-30 motor oil. However I decided to experiment with 5W-20 to see how it behaves, and now the engine runs smoother and the fuel efficiency has increased and allowing 650 km in a single tank of fuel. Thats is 16.7 km per litre for combined route of highway and city. Average Toyota Vios only reaches 450-500 km in a single tank of fuel. Just don't sue me if something wrong happens to your engine while you try to reduce the oil viscosity.
At 125000Km, my engine is still in a good condition. It did not burn the oil, even at reduced viscosity. I started to think if Toyota really designed the engine to use 5W-20 oil, but since by 2008 it was hard to find 5W-20 oil, the manual write that the car requires 5W-30 oil. Well, this is the reason why I dare to try putting 5W-20 oil in my car.
1. My old 2002 Toyota Camry uses the 2AZ-FE engine, which is the same engine used by my 2012 Toyota Vellfire. While my Camry manual recommends 5W-30 oil, Vellfire's manual recommends 0W-20 oil. Therefore the 2AZ-FE engine can accept 0W-20 oil. The same might be true for 1NZ-FE engine on my car.
2. Accoriding to Wikipedia article on SAE viscosity grades: http://en.wikipedia.org/wiki/SAE_viscosity_number#Grades "While it may be confusing that the standard may not specify SAE viscosity, it is not the important parameter. Wear protection and HTHS viscosity are important parameters and are not specified in the SAE viscosity standard."
Therefore I dared to try using 5W-20 and it does really work saving me a lot of money! For 10.000 km, I used to use 689 litre of fuel, now I use only 598 litre of fuel. Thats 91 litre of fuel saved for 10.000 km which translates to IDR 955.500, about 100 USD saving per two months. Very worth the money, considering the price of oil is only IDR 100.000 for 4 litre. More, motherearth loves it too!
Oh yes, I forget to tell you that my car's fuel consumption degrades. When new the car uses 16 km per litre on standard 10W-30 Nissan oil. After 120.000 km, the Vios runs 13.2 km per litre. With my tricks, I can get it back to 16 km per litre on a combined cycle!