Working out miles per litre of petrol

TomsMom

I don't use my car much and let another member of my family use it when they want to. I make a note of my mileage and then will say "Here's £XX for the petrol I've used" (they usually put the petrol in as they use car more than me at the moment).

The dashboard tells me how many miles per gallon the car does, gives a lower and a higher figure so I assume the lower one is for short journeys (which is the majority of use) and the higher one for longer journeys.

As mine are all short journeys, and I know the mileage, how do I work out how much petrol I've used and how much to pay?

Say I'm buying petrol at an average of £1.45 per litre. The dashboard tells me that I'm getting, say, 23mpg. Is there a way I can work out how much I need to pay for the petrol I use if I do, say 50 miles? Insert other figures if it makes it clearer/easier .

Hope I've explained that OK .

Iceweasel

personally I use litres/100Km but never mind.

50 miles needs to be divided by the mpg and multiplied by 4.54

50 divided by 23 = 2.17 X 4.54 = 9.87 near enough 10 litres

So at £1.45 per litre that £14.50

agrinnall

50 miles at 23 mpg uses 50/23 = 2.17 gallons

There are 4.54 litres in a gallon, so 2.17 * 4.54 = 9.85 litres.

And at £1.45 per litre (I hope that's a made up figure as I'm paying £1.27 here) 9.85 * 1.45 = £14.28.

But you really need to look in the car's handbook to find out for sure what the two mpg figures displayed actually represent.

TomsMom

Thank you both, that's really helpful .

agrinnall wrote: »

And at £1.45 per litre (I hope that's a made up figure as I'm paying £1.27 here) 9.85 * 1.45 = £14.28.

But you really need to look in the car's handbook to find out for sure what the two mpg figures displayed actually represent.

Unfortunately not . I live in a fairly rural area, we have one place that sells petrol and it's usually around that price. If I go to the next little town which is 9 miles away I might get it 1p or 2p a litre cheaper. I'm happy to work on the local price as all my mileage is done within about 15 miles of my home.

I'll check the handbook and see what it says about those mpg figures.

PasturesNew

For 23mpg, to keep it simple, at a cost of £1.45 per litre I'd do the following:
1] Move the decimal point of the fuel cost £0.145
2] Multiply x2

So charge them 29p/mile. That's with a lot of assuming and rounding though, but it'd keep it simple

TomsMom

PasturesNew wrote: »

For 23mpg, to keep it simple, at a cost of £1.45 per litre I'd do the following:
1] Move the decimal point of the fuel cost £0.145
2] Multiply x2

So charge them 29p/mile. That's with a lot of assuming and rounding though, but it'd keep it simple

It's charging me really LOL! They put the petrol in, I cough up a bit when I've done a few miles . I'm happy to do rounding, it's very "ish" :rotfl: .

Perhaps I should round down rather than up, after all I'm paying the car tax, MOT, repairs.......... Ah, the things we do for family!

andygb

agrinnall wrote: »

50 miles at 23 mpg uses 50/23 = 2.17 gallons

There are 4.54 litres in a gallon, so 2.17 * 4.54 = 9.85 litres.

And at £1.45 per litre (I hope that's a made up figure as I'm paying £1.27 here) 9.85 * 1.45 = £14.28.

But you really need to look in the car's handbook to find out for sure what the two mpg figures displayed actually represent.

Very good post.:T
And from that simple equation, you have worked out that the car costs about £28.50 per hundred miles in fuel - which is pretty dire IMO.
What you have illustrated, explains why I changed from petrol to deisel for our main car.

photome

andygb wrote: »

Very good post.:T
And from that simple equation, you have worked out that the car costs about £28.50 per hundred miles in fuel - which is pretty dire IMO.
What you have illustrated, explains why I changed from petrol to deisel for our main car.

As the OP does so few miles a diesel would have no benefit

If they really are paying 1.45 for petrol, I hat to think how much diesel is

andygb

photome wrote: »

As the OP does so few miles a diesel would have no benefit

If they really are paying 1.45 for petrol, I hat to think how much diesel is

Not quite true.
If the OP got a smaller petrol car (which would make instant fuel savings) or a diesel without a DPF, then they would also make instant savings.
There are plenty of reliable, cheap diesels which will give a genuine saving the moment you change cars.

bryanb

Try https://www.mpg-calculator.co.uk or similar

TomsMom

andygb wrote: »

Not quite true.
If the OP got a smaller petrol car (which would make instant fuel savings) or a diesel without a DPF, then they would also make instant savings.
There are plenty of reliable, cheap diesels which will give a genuine saving the moment you change cars.

My car is a 5 year old Renault Modus (the smaller version, not the Grande) so I can't go much smaller and this was the most comfortable for me out of all the small cars I tried when it was purchased.

The dire mpg is because the car is not used very often and my journeys are very short, e.g. today I've taken my dog to the groomers, a 3 mile round trip which I walk when the weather is good. The only other time I use it is a 28 mile round trip to take the dog to the forest and that isn't a regular thing.

The other people who use it are my grandson who is learning to drive so someone goes with him for practice but again journeys are usually relatively short although they do occasionally do a longer journey. Or my son or d-i-l occasionally use it when their cars are out of action for whatever reason and again short trips.

It is an expensive convenience I know, but I am happy to keep it on the road while I'm able to afford it and there's a strong chance that my grandson, once he's passed his test, will use it more often, particularly if he's successful in gaining employment.

I've not intention of changing the car and when the time comes for me to give it up I will happily give the car to my grandson (and he takes on the expense of keeping it on the road) in exchange for him letting me use it when I need to or him taking me where I want to go.

I've checked the driver's handbook to find out if my assumption of the figures is correct and the information doesn't tally with what I'm seeing, e.g. book says average fuel consumption is displayed e.g. 5.3L/100 whereas all I'm seeing is 23mpg, so I need to try and sort that out, I'll take the book round to the car later on and go through the whole of the information displayed.

Thanks for everyone's input.