Hello guys,

please what is the best method to calculate the actual fuel consumption. I know vehicle manufacturers have rated millage on their vehicle and I believe this is base on a kind of standard testing.

Would like to know this so I can
1. Know if my car is developing any issue
2. Know the best route that gives me the best fuel economy.
3. And to know the best driving pattern that gives me the best fuel economy

There are two ways to gauge your vehicle's fuel economy: miles per gallon (mpg), which is probably the most common way to phrase it in the good ol' US of A, and gallons per 100 miles (g/100m) which is all newfangled and Euro-style -- sort of like the Daft Punk of fuel economy. It's also a much easier way to compare fuel consumption between two different vehicles. Here's how to calculate either.
Miles per Gallon:
Next time you fill the tank, note the mileage on the odometer, or simply reset the trip odometer to zero.
Drive.
When you fill the tank again, note how many miles you've driven. Let's say you're in a Lamborghini Murcielago and you drove 300 miles. Or more likely, you're in a Geo Metro with a three-cylinder engine and drove 400 miles.
Now look at the receipt (or the gas pump, if you're still at the station and reading this how-to on a mobile device) to see how many gallons of fuel you put in the tank. The Lambo holds 24 gallons and the Metro holds 10.6 gallons; we'll assume you drove until it was completely empty.
The formula is right there in the terminology: miles per gallon. Take the miles driven in the Lamborghini (300) and divide by the number of gallons you added to the tank (24) to get the miles per gallon. That's 12.5 mpg, by the way. The Geo Metro example works out as 400 miles divided by 10.6 gallons = 37.7 mpg.
Bam! You got your miles per gallons right there, math ninjas. And now that you know how to calculate your car's specific mpg, you can reverse that business and find your gallons per hundred miles.
Gallons per 100 Miles:
First, figure out how many gallons of gas you use in one mile by finding the reciprocal of your car's mpg. You were worried, weren't you? Thought you'd have to remember what the heck a reciprocal was all on your own? Relax. It's just dividing one by the number in question -- in this case, the number in question is your car's miles per gallon. So, using the Lamborghini example above, it's 1 divided by 12.5 and for the Geo Metro, it's 1 divided by 37.7.
The answer is your car's gallons per mile. So, that's .08 for the Lamborghini and .026 for the Metro.
Multiply that number by 100, and you've just found your gallons per one hundred miles! It takes 8 gallons to drive 100 miles in the Murcielago and 2.6 gallons to drive the same distance in the Metro.

@kingschild123, well said, very well said.
@op, nice topic

What of someone who doesn't wait for his tank to read empty or reserve what can I use may be inbetween the reading can that be used.

SAW THIS ON A SITE ON THE INTERNET. Its a kind of power point slide that was uploaded on the site, seems much more explanatory that the one Kingschild123 pasted earlier.

HOW TO CALCULATE YOURCAR’S FUEL CONSUMPTION (FC)

• a) Definition Fuel Consumption (FC) is the measurement of fuel usage of a car over the distance covered by that car or in short; The amount of fuel used per distance. Do not confused Fuel Consumption (FC) with Fuel Economy/Efficiency (FE), they are closely related but they are not exactly the same thing.
• b) Unit of Measurement There is no universally accepted standardized unit for Fuel Consumption but the most common measuring unit used for FC is Liter per 100 Km (L/100km). While for FE, the unit of measurement would either be in Miles per Gallon (MPG) or Km per Liter (Km/L)

• 2.0 METHODS OF CALCULATION Two basic methods of calculation (simple mathematics to be honest) will be explained here and will be done in unit of Liter per 100 km (L/100km). Conversion to other useful unit will be showed in the later section.

• a) Rough Estimation For this method, 2 simple info is needed namely (i) the volume of gasoline you’ve spent/used over a specific distance & (ii) the rough estimated distance your car covered in that particular period.

• Example 1;A women traveled to her workplace with hersedan approximately 50km daily (round trip). Inthat distance, her car used up to around 4.7liters of gasoline. Her FC in L/100km would be-FC = 4.7 L / 50 km = 4.7 x 2 L / 50 x 2 km = 9.4 L / 100km @ 9.4 in L/100km

• Example 2; Ahmad journey to his factory & return home daily is 40km. He spent around RM25 of gasoline for 5 days of traveling for work. The FC calculation is as follows; First, RM25 of gasoline at RM1.9 per litre; Gas = 25 / 1.9 = 13.16 liter Second, total distance; Distance = 40 x 5 = 200 km*continue to next slide**price is for Malaysian RON95 Gasoline as at 2012

• Example 2;Hence, Ahmad’s Car FC; =13.16 / 2 L 200 / 2 km = 6.8L / 100 km = 6.8 L / 100km @ 6.8 in L/100km

• b) Careful Calculation Route-based type of driving which is City Driving (uneven road surface & a lot of braking/short stop) & Highway Driving (good road surface condition & smooth driving) shall be determined This will depend on your i) Odometer & ii) Fuel Gauge You’ll need to carefully observe the movement of your fuel indicator/gasoline usage

• b) Careful Calculation (Cont’) Correspondingly you’ll have to note down your mileages from the point you filled up your tank & until the moment it get back to the previous fuel level Note that however this is no guarantee that you would get an accurate value for your car FC, rather an approximation of how your car has perform in consuming its fuel

• Example 3; Chong went to a gas station to fill up his car where he spent about RM 35 (for RM1.9 per litre of gas). At that time, his fuel indicator had only just fall to one bar & his car mileage reading is 75100 km. After a few days of driving his car fuel indicator dropped exactly to one bar of gasoline again. At that particular time, his speedometer clocked 75280 km for his mileage. Note that Chong used federal road to his workplace daily. The FC calculation is as follows;*continue to next slide

• Example 3;First, RM35 of gasoline at RM1.9 per litre;Gas = 35 / 1.9 = 17.5 literSecond, total distance;Distance = 75280 - 75100 = 180 kmHence, Chong’s Car FC; =17.5 L 180 km = 9.7 L / 100 km = 9.7 L / 100km @ 9.7 in L/100km forCity Driving

• Example 4; In a vacation to the North side of the country with his wife Mary, Daniel filled up (once only) his car with a full-tank worth of gasoline (60 liter), right after his fuel indicator blinks a warning for near empty tank. His car mileage is 35500 km the moment he filled up his tank & it clocked 36330 km when his fuel indicator started to blink again when he reached his home. The calculation is as follows; First, Volume of gasoline; Gas = 60 liter*continue to next slide

• Example 4;Second, total distance;Distance = 36330 - 35500 = 830 kmHence, Daniel’s Car FC; =60 L 830 km = 7.2 L / 100 km = 7.2 L / 100km @ 7.2 in L/100km fora combination of Highway & City Driving

• 3.0 CONVERSION TO OTHER UNITa) L / 100 km Miles Per Gallon (MPG)b) L / 100 km Km / Liter*note that when conversion is made to eitherMPG or Km/liter, the value they represent istermed “Fuel Economy” or “Fuel Efficiency”

• 3.0 CONVERSION TO OTHER UNITa) To convert L/100km to MPG,Y (MPG) = 282.58 X (liter / 100 km) and, vice versaX (L/100 km) = 282.58 Y (MPG)*this is a reciprocal function

• 3.0 CONVERSION TO OTHER UNITExample 5;Let say given FC is 6.6 L/100 km, so the MPG is?Y (MPG) = 282.58 6.6 (L / 100 km)Y (MPG) = 282.58 = 42.82 Miles Per Gallon 6.6

• 3.0 CONVERSION TO OTHER UNITb) To convert L/100km to Km/Liter,Z (Km/Liter) = 100 X (Liter/Km)Example 6;What is the Fuel Efficiency (Km/L) for given FC8.5 (L/100 km)?Z (Km/Liter) = 100 = 11.76 km / Liter 8.5 (Liter/Km)

• 4.0 IMPROVING YOUR FCa) Keep Your Speed Below 100Km/h (roughly 60 Mph) or Drive Slowly! Generally speaking, by going over 100Km/h, your FC will suffer, ranging from 20% to 30% of your best FC

• 4.0 IMPROVING YOUR FCb) Don’t Push The Pedal Too Hard Yes, take it easy on the pedal. Speeding and rapid acceleration and braking would reduce your gas mileage up to 20%!

• 4.0 IMPROVING YOUR FCc) Moderation in Air-conditioning The air-con compressor drew its power directly from your engine so it is advisable for you to put the compressor at minimum (and/or your usage!)

• 4.0 IMPROVING YOUR FCd) Avoid idling / Excessive Warm up!e) Avoid bad road condition / traffic congested route

We just got done discussing this.

Guys, stop with the manual tracking and just get an app for your phone.

I use Gas Cubby. Very easy, absolutely efficient, has historical data and can also track other stuff like registration, repairs.

I like it as it gives me a total cost of ownership on all my individual cars.

This app is not on android

domack99: This app is not on android

Yes it is, I know cause I used it on my Note2 and it's also on Blackbery.

In any case there are others.

Good discussion,
Few things to note if you really want to calculate your fuel consumption.
1. Where you buy ur fuel. = If u ar in ♍γ̲̣̣̥ part of the World, watch where u pullover for refuel as so will short fill you if you don't look, some have bad calibration and 10L will end up being just 6L of fuel. So fuel are bad and your car takes more to perform.
2. How you drive the car = hard driving, hard breaking, over speeding, bad uneven road and trafic jam all determines fuel consumption
3. Plugs condition = bad plugs, wrong plugs(it fit in doesn't mean it is the correct spec)know the plug spec of your car and use them right.
4. Payload in the car= unneccesary load/logages in the car contribute to the amount of weight the car is carring about. If it is not needed drop it at home.

Writing from practicalize experience on different vehicles or time.

Evasmil4: Good discussion,
Few things to note if you really want to calculate your fuel consumption.
1. Where you buy ur fuel. = If u ar in ♍γ̲̣̣̥ part of the World, watch where u pullover for refuel as so will short fill you if you don't look, some have bad calibration and 10L will end up being just 6L of fuel. So fuel are bad and your car takes more to perform.
2. How you drive the car = hard driving, hard breaking, over speeding, bad uneven road and trafic jam all determines fuel consumption
3. Plugs condition = bad plugs, wrong plugs(it fit in doesn't mean it is the correct spec)know the plug spec of your car and use them right.
4. Payload in the car= unneccesary load/logages in the car contribute to the amount of weight the car is carring about. If it is not needed drop it at home.

Writing from practicalize experience on different vehicles or time.

Agrred with you, if the fueling is not accurate, it could throw you into confusion, thinking you are consuming more fuel.

domack99:

Agrred with you, if the fueling is not accurate, it could throw you into confusion, thinking you are consuming more fuel.

And this is why I recommend an app, though you still have to watch for garbage data entry.

Good morning NL,
Please I want to know the actual liters in gallon used in nigeria.

E.g
1 US gallon is 3.8 to 4 liters in Nigeria
1 UK gallon is 4.3 to 4.5 liters in Nigeria.

Which one is in use in Nigeria.

UK or US gallon?