Hacker Read top | best | new | newcomments | leaders | about | bookmarklet login

They're probably accurate to within less than 10%. How many kilometers would you have to drive to save a dollar from slightly bigger tyres?


sort by: page size:

5.8 grams per kilometer would mean in only 10,000 KM your tyres lose 58 Kg. Seems way off.

How many KM remaining depends on the terrain, traffic, driving technique, weather and a host of other factors. Nobody is expecting 100% accuracy just a rough estimate. They are already mentally doing the conversion anyways.

This is true -- my understanding is that Germany actually requires they never read low EVEN IF FITTED WITH THE WRONG SIZE TIRES which is sort of insane.

That said, I believe the odometers are typically bang on, which would mean the mileage calculation should be accurate. Or could be, if they wanted it to be.


Afaik it’s more like 10% per 1000km

> My 2016 ICE car's "miles left" meter is accurate to +/- 2 miles from the moment I top up the tank (80% highway driving, 20% hilly city and rolling country roads).

No way. That’d be accurate to under 1% - well within the variation you’ll get just from different air densities (temperature, pressure, humidity). Forget about A/C on or off, tire pressure, etc.

It’s gotta be tricking you somehow.


Divide your miles by 10 and they seem about right.

You're lucky, I have, several times in Germany, where some dealers come with a ruler measuring them, plus km limits per day.

I did the calculation in Freedom Units and converted to grams per km. Assuming tires last 60,000 miles or 100,000km and got 0.1 gm/km. So matches your analysis closely.

Notable I put 60,000 miles on my cars tires since I bought it. They are due for replacement kind of whenever.


6.7% per 1000km is .65% per 100km which is almost exactly 1% per 100miles, as GP said.

So it's just off by a factor two if you compare with DC.


For example, when driving a long distance (150m+), it told me that I could have saved X miles if my tires were inflated another 5psi, and saved Y miles if I had used less cabin heating.

3.5% per 1000km.

Or you can use some basic math, and calculate how much tire/breaks wears(loses original matter) per 100 000 km and how mach of gas a car burns for the same distance and compare these numbers.

This sounds pretty reasonable actually, but it would need to account for miles driven too. Does Norway?

I disagree. First, the human mind is not that good at dealing with decimal and numbers between 0 and 1. My car is rated 4.5l / 100 km, which is easier to deal with than 0.045l / km.

For a simple calculation, say 5km, what the easiest 0.045 * 5 or (4.5/10)/2 ?

Secondly, a car is designed to be driven over distance, so making measurement on only one kilometer wouldn't be representative of real world usage.


Well, I wouldn't be surprised if the software internally always computed l/100km and the converted to mpg for display.

I would like to see those statistics normalised by the kilometres travelled. Unless they are, I'd argue those are misleading.

I have my car set to display L/100km, but that's mostly because it's a hybrid and so kW/100km is more logical than the inverse and it makes sense to have them both operating the same way.

My previous car didn't have an economy reading anyway, so my only frame of reference before was calculating pence per mile rather than MPG. L/100km seems logical and I had got used to it in a matter of weeks. Mine is generally around 5-6L/100km on long, mostly petrol journeys, so this is now my new mental benchmark, and it's also trivial to go from this to pence per litre, and not much more to get to the pence per mile that I thought in before. I guess my brain has got good at multiplying by 1.6 as I use km for running and cycling too.


> Unless I've really messed up my math,

You have.

The chart is in (g per 100 kcal)

>"magic math" and change them from 42 g/km to 229g/km.

42 is for production of the car 229 is for ‘well to wheel' emissions (i.e. exhaust-pipe plus those emitted to produce the petrol).

No "magic" required.


I've never heard anyone say that. Who are these people that are reading fuel consumption in their dashboard and doing the mental arithmetic to convert that to km/liter? I've only heard "my car spends about 5-8", meaning 5-8 l/100 km in casual conversation. I.e. the number you'd read directly from the dashboard.
next

Legal | privacy