“O” Level maths question: S3 petrol consumption
Discussion
At the beginning of the month I had my petrol tank professionally drained, checked with a borescope, and given a (literally) clean bill of health. The sender had been replaced by the previous owner but was a bit erratic, nothing new about that…. With 25 litres of fuel put back in, the gauge was still showing empty, so the sender arm was adjusted to show between a quarter and a half full. Topping it up with the remaining 20 litres that had been drained, it showed full. However I know the capacity is supposed to be 54 litres, and give range of approx 260 miles. Since then I have driven 160 miles, and refilled with a further 20 litres, so the gauge again shows full but I know it isn’t – but also don’t know exactly how full it actually is. I passed O and A level maths, albeit a long time ago, and worked as a statistician for many years, but this one has me stumped. So the question is:
1. What is my fuel consumption ?
2. For a further 10 points, how many miles can I travel before running out of fuel ?
3. And after Brexit please can we have mpg back ?
1. What is my fuel consumption ?
2. For a further 10 points, how many miles can I travel before running out of fuel ?
3. And after Brexit please can we have mpg back ?
The fuel gauge is useless. Well the gauge is probably OK but the sender is crap. I've lost count of the hours I've spent messing about with the float level trying to get the gauge accurate. I work on filling up every 220 miles to be on the safe side. All you need to do is brim the tank, drive 250 miles and brim it again. Then just do the maths and you'll know your range. Easy peesy 
There are unknowns you haven't removed, which you need to. You don't know how much fuel you've actually used, since you cannot measure the difference.
You need your starting and ending fuel to be equal, or the discrepancy minimised, by refilling multiple times. Brim the tank, drive a known distance, brim the tank, calculate.
You need your starting and ending fuel to be equal, or the discrepancy minimised, by refilling multiple times. Brim the tank, drive a known distance, brim the tank, calculate.
Assuming your tank and lines are now clean, stick a jerry can in your boot, once the gauge shows empty see how many miles you can get before it conks out.
Now you know how many miles you can achieve on ‘empty’, does anything else matter?
If it does, buy a solar powered milk float
Now you know how many miles you can achieve on ‘empty’, does anything else matter?
If it does, buy a solar powered milk float
Edited by LawrieS on Thursday 31st May 22:24
Thanks chaps for varying degrees of helpfulness ! The tank cleaning-out was part of a process to identify what was causing sporadic fuel-feed issues (traced to the internal filter, now replaced). BTW I had also initially suspected an ignition issue, but having changed the coil and replaced some slightly suspect wiring, that's now 100%. Anyhow agreed on all the above points, I'm just a teensy bit worried about the "drive until you conk" option in case I'm somewhere on a major/motorway at the time which is really not a good place to be. As this is my 5th S, I know that the consumption is likely to really be in the 20-something mpg's, so I shall continue to refill every 150-200 miles and keep a detailed log of consumption. That's the trouble when you retire, you get really worried about world issues such as war, disease and famine, and why Waitrose have wrecked their free coffee deal, and which sock to put on first.
lordofthewings said:
At the beginning of the month I had my petrol tank professionally drained, checked with a borescope, and given a (literally) clean bill of health. The sender had been replaced by the previous owner but was a bit erratic, nothing new about that…. With 25 litres of fuel put back in, the gauge was still showing empty, so the sender arm was adjusted to show between a quarter and a half full. Topping it up with the remaining 20 litres that had been drained, it showed full. However I know the capacity is supposed to be 54 litres, and give range of approx 260 miles. Since then I have driven 160 miles, and refilled with a further 20 litres, so the gauge again shows full but I know it isn’t – but also don’t know exactly how full it actually is. I passed O and A level maths, albeit a long time ago, and worked as a statistician for many years, but this one has me stumped. So the question is:
1. What is my fuel consumption ?
2. For a further 10 points, how many miles can I travel before running out of fuel ?
3. And after Brexit please can we have mpg back ?
1. Use a gps- app on your phone to track driving distance and always fill up full, then it’s easy to calculate 1. What is my fuel consumption ?
2. For a further 10 points, how many miles can I travel before running out of fuel ?
3. And after Brexit please can we have mpg back ?
2. On the eurotour my s3 did 9,3l/100km
3. NO!!!
Stick the fuelio app on your phone. Brim the tank
Drive around
Brim the tank again
Put data into fuelio
Works out and keeps track of mpg for you.
Dimples.
Although it isn't really as it shows the differences in mpg you get when your right foot starts to play. Mine has varied betwwen 40 and 20 mpg.
But does it really matter how accurate it is really? Wait until it gets near the bottom, allowing a margin for safety then refill.
If you're retired you should have plenty of time to just pop off and buy fuel
Drive around
Brim the tank again
Put data into fuelio
Works out and keeps track of mpg for you.
Dimples.
Although it isn't really as it shows the differences in mpg you get when your right foot starts to play. Mine has varied betwwen 40 and 20 mpg.
But does it really matter how accurate it is really? Wait until it gets near the bottom, allowing a margin for safety then refill.
If you're retired you should have plenty of time to just pop off and buy fuel
lordofthewings said:
Maffe said:
1. Use a gps- app on your phone to track driving distance and always fill up full, then it’s easy to calculate
Memo to self: finally move into the 21st century and buy a smart phone, rather than the old Nokia that I still use...I inadvertently left "Location" switched on on my phone, and it burned though a whole month's data allowance in two days!
Plus the b
ds know where you are...
I was reading a safety operators report involving a plane that ran out of fuel
Turns out the fuel use calculator is only as good as the operator
I tend to brim tank. Then do 200 miles regardless of conditions then brim tank again a few times and you get a good average of what fuel you’ve used. Ignore the gauge until you know what these figures are. You might want to use a gps if your unsure of your milometre readings.
Turns out the fuel use calculator is only as good as the operator
I tend to brim tank. Then do 200 miles regardless of conditions then brim tank again a few times and you get a good average of what fuel you’ve used. Ignore the gauge until you know what these figures are. You might want to use a gps if your unsure of your milometre readings.
...bragging eh ? In 1978 I collected my new Taimar from the factory, and drove south stopping overnight at my parents' home in the New Forest, then onto the ferry to France and next stop (apart from refuelling) was Zurich where I was living/working at the time
, fantastic trip and fuel consumption was just under 30mpg overall (a lot of Motorway cruising). OK done with bragging, pic of car below, last heard of a few years ago, who has it now ?
, fantastic trip and fuel consumption was just under 30mpg overall (a lot of Motorway cruising). OK done with bragging, pic of car below, last heard of a few years ago, who has it now ?Gassing Station | S Series | Top of Page | What's New | My Stuff