How To Calculate Your Car's Fuel Economy?


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How do you check the fuell efficiency and which method is accurate

Have you ever had question like how do you check the fuel efficiency of your vehicle , have your peers told you various methods to check efficiency.

What method should you use ? Which one gives correct figures? If these are questions running in your mind then you ‘ve came to the right place
Welcome to THE AUTOMOTIVE INDIA and this is afrose3 , so how do you check the mileage of your vehicle ,tankfull to tankfull or that worderfull bottle method. In this thread I will be sharing my experience that I had and you will come to know why everyone recommends tankfull to tankfull method .

So I started today and I was curious to try I took a 2lt bottle with me and got it filled with petrol and went to the outer ring road I drived my car untill it was out of petrol . I gave it a few cranks to make sure that it out of fuel I agree im dumb:agree: and stopped the car downhill ,this was my first mistake came out of the car and poured exactly one litre in the tank and cranked the engine after 6-8 cranks the engine started and I started driving at 40kph . To my surprise it stopped after 24.7 km .


Then again I gave some 8-10 cranks to make sure that the fuel is finished. Now here starts the adventure , so got out of the car and poured the rest 1lt petrol I had and started calculating that how I got so good figure I thought there must have been some fuel left even after cranking while thinking I cranked the engine no it refused to start. Then cranked some 8-10 times still of no use now I started worrying. This was my second mistake.


After cranking the engine so many times the battery came down. Now I told to myself that I had done some thing to it and lets start it by bump method ( I don’t know how to start by this method) so pushed the car and sat inside quickly and removed my foot from clutch still no use.
Then came a good Samaritan in type 1 maruti 800 hoping that he would help , I waved my hand to get his attention. He was around 55-60 years . He came and asked to open bonnet and tried to find out the fuel line that goes to carburetor but couldnt and told that petrol must come out of it when I crank and asked how it all happened and after listening that he got frustrated and showered lecture on me telling that “ you boys of this age always want to take risks and think of becoming noted every where for your risks , here it is take this adventure “I simply nodded to him then he told me he would drop to near by local mechanic but I refused .


Then came the second good Samaritan in zen D as I was pushing the car up to try bump start he parked his car and came to me and asked what’s the problem I told him everything , then he said have you tried bump start I said no and gave keys to him and pushed the car and voila it started and stalled then again pushed with all force and it started again , then I asked him how he did that he said I cranked so much that the fuel line was filled with air then my common sense came to light.

I thanked him from depth of my heart. then I told him about the air lock, he told that the bosch pump would lock and I don’t need to worry and asked me to check if it stalls again but it dint stall this time and i reached my house safely.

That’s how it ended , I would never recommend any one to go with bottle

1) Why shouldn’t I go for the bottle method and why only the tankfull method?

Ans : The bottle method is risky business to deal and since petrol is volatile it evaporates more when there is more space in tank and where as if tank is full or half the rate of evaporation is far less.

2) Oh I cant wait so long to check my FE what shall I do?

Ans : After you get the tank filled drive atleast 100 km so that you have consumed 5-8 lts so that there is room for fuel go to petrol bunk and fill the tank. Now divide the number of liters required to fill tank to full by 100 since you have driven 100km. There you that’s your FE.

3) I’ve heard people telling to remove unnecessary weight to get good FE , wont a full tank be unnecessary weight?

Ans: Yes removing unnecessary weight indeed increases FE, but there’s not going to be that much appreciable change and it is better than keeping half tank empty for evaporation and far more better than that bottle method risk.

4) How do I manage to get good FE in traffic?

Ans: If there is bumper to bumper moving traffic drive at a constant speed of moving traffic in correct gear .

THANKS for bearing with me and reading my boring story[:D]
 
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Re: How To Calculate Your Car's Fuel Economy / Mileage?

i go by tank full top up method for petrol and same for CNG gives me approx results which are useful
that fuel dispenser part was nicely shared
so that translates too that we should target pumps with large fuel dispensers ?
 
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Re: How do you check the fuell efficiency and which method is accurate

That’s how it ended , I would never recommend any one to go with bottle
Weird trial Dude... You got better saved as your's is a Petrol Engine. If it was Diesel, you would probably never have started her again, until you pump the fuel manually or take her to a workshop.
 
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Re: How To Calculate Your Car's Fuel Economy / Mileage?

I am using 1 month old New Spark LPG

Although it is due for 1st servicing
calculate FE of LPG it is giving around 14

I do tank full LPG (85% of actual ie 25 litrs) SET TRIPMETER To zero and run on LPG till car switches automatic to petrol mode write down trip reading when switch-over happens.For spark when LPG goes in reserve it giving Beep alarm till Tank empty
 
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How shall I calculate mileage?

My Ritz VXI Petrol has clocked only 333 kms which I bought on 31st January,2013.
I am not understanding how to calculate fuel consumption through the multi functional instrumental panel. It always shows 4.9 lt/100km as an average. I guess I am doing something silly.

I know the best practise is from tank full to tank full.
 
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Re: How shall I calculate mileage?

The information that the instrument panel is showing is that you are using 4.9 litres to travel 100 Kms so the average comes out to be close to 20.4 litres however this is not accurate as in my Dzire also the instrument panel shows around 20.5 (I did reset it) however when I calculated the same using tank full to tank full method it was around 19.2 KM.

You may refer to the manual which you must have got with the car which states how you can swith between the various settings in the instrument panel.
 

sethumurugan

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Re: How shall I calculate mileage?

I am using 1 month old New Spark LPG

Although it is due for 1st servicing
calculate FE of LPG it is giving around 14

I do tank full LPG (85% of actual ie 25 litrs) SET TRIPMETER To zero and run on LPG till car switches automatic to petrol mode write down trip reading when switch-over happens.For spark when LPG goes in reserve it giving Beep alarm till Tank empty
Sanju, i think I missed this post of yours. Even though I have same spark LPG LS model and i do the same way as you do in LPG. But Mine is very less compared to yours. Mine comes between 8-10 in city.

What ever you have mentioned is in city or in highways?

My Ritz VXI Petrol has clocked only 333 kms which I bought on 31st January,2013.
I am not understanding how to calculate fuel consumption through the multi functional instrumental panel. It always shows 4.9 lt/100km as an average. I guess I am doing something silly.

I know the best practise is from tank full to tank full.
I think Mr. RK could be the right person [as far as I know] who can help you, who owns a Ritz.
 
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Re: How shall I calculate mileage?

My Ritz VXI Petrol has clocked only 333 kms which I bought on 31st January,2013.
I am not understanding how to calculate fuel consumption through the multi functional instrumental panel. It always shows 4.9 lt/100km as an average. I guess I am doing something silly.

I know the best practise is from tank full to tank full.
Rakesh,

If you have an android phone download Car management applications which would also help you calculate the mileage of your car. To name a few : acar, fuellog.

These apps would not just calculate you mileage but manage your averall car expenses.
 
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Re: How To Calculate Your Car's Fuel Economy / Mileage?

@Rakesh

I own a Ritz but diesel, ok I do not have any MFD in my car so I check the FE like this

1. Tank full to Tank full method, which is common every body does it. Fill the tank full and set the counter zero and check it when entire fuel comes to empty

2. There are dots to show fuel in our car, when last dot start blinking, immediately I look for a fuel pump and fill either Rs.500 or 1000 and set the counter to zero and I will check till the next time the lost dot starts blinking.

Hope it is clear to you now[:)]
 
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Re: How shall I calculate mileage?

Sanju, i think I missed this post of yours. Even though I have same spark LPG LS model and i do the same way as you do in LPG. But Mine is very less compared to yours. Mine comes between 8-10 in city.

What ever you have mentioned is in city or in highways?



In city without AC.i got above figures.
Petrol around 13-14 without AC
 
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Re: How shall I calculate mileage?

Rakesh,

If you have an android phone download Car management applications which would also help you calculate the mileage of your car. To name a few : acar, fuellog.

These apps would not just calculate you mileage but manage your averall car expenses.
Unfortunately I don't have an android phone but thanks buddy for the tip.
 
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Re: How To Calculate Your Car's Fuel Economy / Mileage?

@Rakesh

I own a Ritz but diesel, ok I do not have any MFD in my car so I check the FE like this

1. Tank full to Tank full method, which is common every body does it. Fill the tank full and set the counter zero and check it when entire fuel comes to empty

2. There are dots to show fuel in our car, when last dot start blinking, immediately I look for a fuel pump and fill either Rs.500 or 1000 and set the counter to zero and I will check till the next time the lost dot starts blinking.

Hope it is clear to you now[:)]
Infact this isnt how tankful method is done and both options you suggested will not yield accurate results check out post #16 suggested by tough guy - thats practically how accurate it could get though i will also attempt to see if OBD2 data can come close to this. this is assuming you havent upsized etc in which case you need to apply a further correction.
 
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Re: How To Calculate Your Car's Fuel Economy / Mileage?

Infact this isnt how tankful method is done and both options you suggested will not yield accurate results check out post #16 suggested by tough guy - thats practically how accurate it could get though i will also attempt to see if OBD2 data can come close to this. this is assuming you havent upsized etc in which case you need to apply a further correction.
OK, IR I will do that this time as mentioned by TG, mine are not upsized and stock one just as it is from showroom no extra things anywhere[:)]
 
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