Calculating litres used.

Joey the lips

Hi Folks.

I wondered if you can help. As stupid as it sounds I need to know how many litres of petrol i use on 100 km. Forgive the stupidity of the question but my reason is genuine. I am entitled to claim duty back under the disabled drivers scheme when i carry my child however there is 2 days when i dont and i am having difficlulty at the moment calculating this.

I figure at the moment 55 euro lasts me 400km roughly so 100 kilometers is roughly 13 euro so all i need to do is divide 13 by the price per ltr which is 1,30 this 10 ltrs.

So i estimate that 10 ltrs on each recept should not be claimed for.

But surly there is a more scientific way.

Thank you

So I

Wheelnut

That calculation seems alright to me. What do you mean by "more scientific"?

brownej

You're doing it correctly but you might want to approach it in a slightly different way.
I'm assuming that your car can't tell you the fuel efficiency itself.

You might want to calculate based on fuel consumed and then convert to money afterwards as 55 euros might get you 400km this week but when petrol goes up in price it'll only get you 380km next week while the litres/100km isn't going to change much if you're like most people and drive the same routes week in week out in the same way.

Long term it can be straight forward enough to calculate engine efficiency. Take an odometer reading everytime you fill up. Fill up at the same needle point on the gauge all the time and put the same amount of fuel in for example 40litres. It's all the same to the garage if the money isn't rounded. After a few weeks you will build up a very clear picture of the long term fuel efficiency of the car.
Then for your claim just use your pre calculated litres/100km figure for the car for the amount of kilometres you want to claim for.

Joey the lips

Wheelnut wrote: »

That calculation seems alright to me. What do you mean by "more scientific"?

I dont know is there stats that the car burns so many lts per km or something like that....

But if my calculation is close...at least i know i am being fair with the system.

Joey the lips

brownej wrote: »

You're doing it correctly but you might want to approach it in a slightly different way.
I'm assuming that your car can't tell you the fuel efficiency itself.

You might want to calculate based on fuel consumed and then convert to money afterwards as 55 euros might get you 400km this week but when petrol goes up in price it'll only get you 380km next week while the litres/100km isn't going to change much if you're like most people and drive the same routes week in week out in the same way.

Long term it can be straight forward enough to calculate engine efficiency. Take an odometer reading everytime you fill up. Fill up at the same needle point on the gauge all the time and put the same amount of fuel in for example 40litres. It's all the same to the garage if the money isn't rounded. After a few weeks you will build up a very clear picture of the long term fuel efficiency of the car.
Then for your claim just use your pre calculated litres/100km figure for the car for the amount of kilometres you want to claim for.

I am slightly confused but will see if i can figure. So if i fill up with the odometer at 1000km and it costs me 50 euro and i fill up again with the odo at 1400km and it cost me 55 euro then its fair to say it cost me 55 euro for 400km so 100 km cost me 1/4 or 13 euro roughly. so if petrol that time is 1.30 per ltr thats 13 divided by 1.30 for that week

This is the best way, brim the car to the top full of fuel. Zero the odometer. Note from the odometer the miles / kms travelled that you can claim for. After x amount of miles, brim the tank again. Note how many litres used and the distance travelled. You can calculate the cars litre/km rate then. Then use that and the mileage travelled that you can claim for the work out how much cash to claim. Don't go off manufacturers specs as they aren't really real world.

Hope that helps

Wheelnut

Joey the lips wrote: »

I dont know is there stats that the car burns so many lts per km or something like that....

Yes there are figures published by the makers but they are not much use in the real world. Each new model is put through a test and the consumption is recorded. This serves for the customer to see if car A is more economical than car B etc. In the real world every driver is going to get a different consumption depending on his style and the driving conditions.

You are doing the correct thing by figuring out the cost of the journeys, but as Brownej points out, the cost will vary with the price of fuel even though your MPG stays the same.

brownej

Sorry I'm not being clear at all.

If you drive the same way all the time. Same routes etc etc then your engine efficiency should be very consistent from week to week. (unless there is something wrong)
So if you calculate your engine efficiency over a few weeks and get a litres/100km for that then just use that number every time.

To do this you need to be consistent about the way you calculate the numbers.

Put petrol in the car at the same fuel tank level for example exactly a quarter full.
Put a fixed amount of fuel in say 40 litres.
take an odometer reading lets say thats at 12000km

The next time you fill up at the quarter tank mark do the same thing.
If for example your odomoeter ready 12400km then you know that 40litres gets you 400km.
do this over a few fills and it will build up a long term pattern.

If after 4 times doing this your odometer reads 13650 then you know that you've put 160litres of fuel in and have travelled 1650 kilometers. thats a long term average of 10.3 litres per 100km (1650/160)
So anytime you need to claim you just say that on average the car consumes 10.3 litre/100kms. I travelled 250km this week that I can claim for. Thats 25.75litres of fuel. Fuel is €1.33 this week so I claim 25.75*1.33 so €34.25

The long term efficiency of your car won't change much but the price of petrol will.

mickdw

You are being very honest with the system I must say. Many many people in your situation would just claim as much as possible given the chance. Its great to see. I wouldnt worry about the exact figures. Somewhere between 7 & 10 L/100km is reasonable.

You obviously dont subscribe to the Ivor Callely school of economics!

Joey the lips

mickdw wrote: »

You are being very honest with the system I must say. Many many people in your situation would just claim as much as possible given the chance. Its great to see. I wouldnt worry about the exact figures. Somewhere between 7 & 10 L/100km is reasonable.

You obviously dont subscribe to the Ivor Callely school of economics!

I have never been dishonest bar white lies. I would imagine i have guilt written all over me. I am well known through the youth service so it would not serve me well.
But thanks

I just want to make sure I am doing right seen as though the govt gave me the resource.