Car owners always remain concerned about the fuel efficiency of their cars, and why should they not be….. it saves money. In this blog i’d recommend some measures for “How to improve MPG of car (Mileage per gallon or per liter)”. MPG of Car depends on multiple factors, some are manageable at individual level while the others might require deeper maintenance techniques, and help from specialist technicians. But remember MPG of car has inverse relation to the friction /resistance to free movement of a car. This resistance to movement could either be because of the performance of the engine or due to external factors causing restriction to free movement of the car. These factors are briefly discussed below.
In subsequent paragraphs I’ve categorized MPG impacting factors into two main categories i.e factors manageable at individual level, and factors requiring relatively deeper maintenance action which are manageable at technicians level. But in my opinion car owners must have slight knowledge on both because technician level measures will make you more knowledgeable about your car and you can always discuss the issue with technician with more confidence. I’ll try to keep the things simple and will be explained in simple English so that everyone can understand the discussion. So let’s begin….
1. Individual Level Measures
Drivers / owners may take following measures at individual level to improve MPG / MPL of their cars:-
(a) Driving styles
Car driver plays a vital role in good or bad MPG of a car through their driving styles. Driving style includes but not limited to the following aspects, which if managed carefully will improve the MPG of car:-
(i) Foot Manipulation for Accelerator
Driving with light foot increases the MPG of the car. Driver must be cautious while accelerating and should not press the accelerator too hard to gain desired speed. It, however, sometimes become difficult if the average road speed of other drivers is more than yours. So it has to be a best balance between the light foot and the average road speeds.
(ii) Brake Application
In order to improve the MPG of car, one must try to apply limited brake at the known points of stops such as at traffic signals / destinations. At such points the car may be stopped by normal deceleration without application of brakes, this style is also known as gliding.
(iii) Gear Shifting Behavior
Shifting behavior is more significant in manual transmission cars, but that does not mean that gear shifting cannot be manipulated in auto-transmission cars – it certainly can be. In either of the cases the gear transition should be kept soft with light acceleration and least revving of engine.
(iv) Use of Air Conditioning
The more Air Conditioning is used the lower will be the MPG. Always take it normal to have lower MPG with AirCon ON. How much effect on MPG with AirCon is little difficult to define because it varies on multiple factors such as engine condition and capacity (cc), AC compressor efficiency, AC Compressor bearing condition, load on the car in terms of people and heat load etc etc. But generally speaking AC decreases 25-30% MPG of the car.
(b) Route Selection / Road Condition
Route with minimal traffic should be selected for better MPG of your car. Also the road and traffic conditions greatly affect the fuel consumption of an automobile. If there are more traffic signals on a road or there are numerous speed-breakers or zebra crossings, then the MPG of the car will get adversely affected. Hence, right selection of route and road will positively contribute towards improvement of MPG of car. Similarly, if the route comprises of a hilly terrain, then MPG will always be low for uphill drive and vice versa (you know it !!!).
(c) Load in the Car
More load in the car means more resistance to free movement of the car, hence low MPG will be recorded. The usage of two similar cars with different loading conditions will report different MPGs. The car with more loading will always have a low MPG. To improve MPG, loading of car needs to be managed in an better way.
(d) Tire Size and Tire Pressure
Tires play a major role in MPG of car, because it is the only part of the car that comes in contact with the road and is a point of friction for movement. It is advisable to always use manufacturers’ recommended tire size as it is designed for best possible MPG vis-a-vis the engine/load capacity of the car. Similarly tire pressure should also be maintained according to the user’s manual. Tire size and pressure impacts the MPG in following ways:-
(i) Wider tire size increases the contact area with ground causing more friction to movement, hence low MPG will be observed. Just a word of caution that narrower (than recommended) tires may cause braking issue and could be dangerous.
(ii) Low tire pressure flattens the tire thereby increasing the contact area with ground causing more friction (as we experience heavy drive with flatten tire). Hence less tire pressure will adversely effect the MPG of car. It is recommended that regardless of the appearance, the tire pressure must be checked at least on monthly basis and should be equalized for smoother drive.
(e) Oils and Filters Selection
I’m including this aspect in individuals’ category because it is the prime responsibility of the owner to select the correct grade of Oil and filters for their cars in accordance with the manufacturer’s recommendations mentioned in car user manuals. Correct grade and quality of engine oil not only increases the life of the engine but also contributes towards better MPG of car. Similarly, correct grade and quality of transmission oil also plays a positive role in friction-less drive. Replacement of lubricants and filters as per the defined periodicity will save you money in terms of extended and trouble-free life of your car as well as improved MPG with smoother drive. Word of advice “Never ever compromise on quality of lubricants and especially the quality of filters”.
2. Technician Level Measures
The factors that affect the MPG of car and require relatively deeper maintenance, special tooling and expertise are listed below for the understanding of the non-techies. I, therefore prefer not to make it a technical discussion, but only an overview of the causes of low car MPG:-
(a) Catchy brakes
Catchy brakes may increase the drag force and results in poor car MPG. This can be judges by comparing the tire/rim temperature among the four wheels. Higher temperature clues for higher friction could be caused by catchy brakes. The symptom of catchy brakes is resistance to free rolling of car at lower speeds. Whenever some maintenance is done on brakes or wheels, the driver must pay special attention and check the temperature of wheels for next 2-3 drives.
(b) Wheel bearings
Faulty wheel bearings also induce friction to the free rotation of the wheel hubs. The symptoms of faulty wheel bearing is grinding noise during high speed driving or sometime the noise only heard during slight veering of car during straight drive. Faulty bearing(s) also increases the temperature of the wheel rim
(c) Engine tuning
Most of the modern cars are self tuned through ECMs (Electronic Control Module), yet there are factors that varies the engine settings that needs to be reset periodically, these are:-
(i) Engine Tappet settings
In a layman language ‘Tappets’ are the linkages that are operated by the engine drive in order to open/close engine values. Tappets are prone to get loose over a period of time which may cause excessive engine noise, loss of power or rough running. These factors results in extra fuel comsumption and low efficiency of the engine. If not as per the adjustment, tappets may also cause hard engine running or hesitation in acceleration.
(ii) Valve Clearances
Worn out engine valves may cause loss of power, misfires and low MPG of car.
(iii) Spark Plugs
MPG of car is greatly effected by the condition of Spark plugs. Spark plugs cause low MPG if they become dirty with carbon deposits or get worn out due to extended usage. Spark plugs are life-items that needs to be replaced after a specific mileage of the car. Generally the life spark plugs is 50,000 KMs to 75,000 KMs). If the fuel quality has high lead contents, then the spark plugs must be replaced earlier. In such cases it is better to replace spark plugs at 75% of the defined mileage.
(d) Coolant and Thermostat Valve
Thermostat valve in engine cooling system ensures that the car engine run at optimal temperature. MPG is best if the engine runs at optimal temperature usually 80-90 deg Celsius. Especially if engine runs at low temperatures the ECM (Electronic Control Module) will make the mixture rich causing low MPG. Similarly, if the engine operates at high temperatures, it will cause lean mixture, resulting in higher throttle setting to achieve desired acceleration / speed causing low MPG of car. Hence engine coolant and thermostat vale plays a vital role in optimal performance of the engine.
(e) Lambda / Oxygen O2 Sensor
Lambda / Oxygen sensor ensures environment friendly exhaust gases from the car. If the O2 sensor fails, it may cause rich / lean mixture resulting in low MPG. O2 sensor may be cleaned periodically or if completely failed it will throw 0420 code for OBD2 compliant cars.
(f) Catalytic Converter Condition
Depending on the mileage of the car and the quality of the fuel used, the Catalytic converter may get clogged due to carbon deposits. Indications of clogged ‘CAT’ are loss of power, non-responsive throttle, high idle RPMs or smelly exhaust gases. Cheaper solution is to clean the CAT, but its a temporary solution, best is to replace the CAT with a new one.
These were the few salient factors that can adversely effect the MPG of car. It is hoped that this article must have been helpful for you, if you have liked it, Please Subscribe to my website and share this blog on your social network through sharing bar on the left.
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