Understanding the relationship of fuel consumptions and engine loads and oxygen sensor

I've done quite an extensive research about car's fuel consumptions - but little did I know that it is actually quite simple. Back to the basic principle of all engine's which consume fuels based on the load it has to carry which means more loads more fuels. Just like electric motors the heavier the motors the more Amperage it use to spin the motors. Let's focus specifically on car's fuel consumptions.

1. Car running without air conditioner save more fuels - although it is not the most desirable but it is true that if you are running car's without the A/C on it will save lot's of fuels. This is tested on OBD2 ecu scanner where fuel consumptions increase significantly when air conditioner is turned on. The technical principle behind this is very simple as the A/C system is turned the compressor magnetic clutch automatically engage to add more loads to the engine. As a result more fuels are needed to run the A/C compressor unit. Apart from that radiator fan and cabin blower fan also turned on giving signal to the ECU to command the alternator to work harder to stabilize the current which also increase fuel consumptions.

2. Aging cars - as the pulleys, bearings, and driveshaft, power steering, transmission, and internal engine parts worn out over time. It will add more frictions which mean loads and leads to more fuel consumptions to turns those parts. The components potential list of components.

• Alternator pulley and bearing
• Water pump pulley
• Crankshaft pulley
• Power steering pump
• Tensioner pulley
• Serpentine belt
• Driveshaft bearing
• Power steering

3. Over mileage used of engine oil and transmission fluids will loose its lubrications effectiveness on the engine and gearbox which leads to more loads. 

4. Bad car braking system - such as seized brake pads and brake drums could also increase loads which require more fuels to burn.

5. More passengers or loads inside the car obviously increase more engine loads.

6. Climbing uphill also increase engine loads.

7. Cruising car on the road save more fuels based on the average reading vs on Idle. As the car cruising on the road its load is lighter than having to move from initial positions. Just like a simple electric motors require more current to kick at the initial start and less current as it already spinning.

8. Changing gears too frequently also increase more loads example in automatic transmissions changing the gear will consume more fuels on every shift either from Parking to Drive or Parking to Neutral or Vice versa. This is because of torque changes at every gear shift add loads at the initial engagement.

Oxygen Sensor (O2 Sensor).

Perhaps we are too naïve thinking that the oxygen sensor of the car contribute to significant fuel consumptions. Theoretically yes maybe but it's main purpose only capture combustion activity (oxygen) and send the data to the ECU to make adjustment from the basic fuel consumptions which based on the engine's loads. 

The O2 sensor does not adjust to the point that where the car can't run due to heavy loads for the sake of fuel economy. Which means fuel consumptions of a car always benchmark by the loads and then adjusted by the oxygen sensor. So in my opinion the O2 sensor play little roles in car's fuel consumption. 

However if the O2 sensor happen to be faulty - the car will display check engine light or might not turn on at all. But a worn out O2 sensor will still work only that providing the ECU with inconsistent data but the car will be able to run and carry the loads that it is capable of handling.