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#1
09-23-2007, 11:32 PM
 Unregistered Guest Posts: n/a
liter per 100 km to MPG

Hi, need help with my rusty algebra to come up with a formula for this conversion.

This is the way gas milerage is rated in Australia, liters per 100km, I can do the math to make the conversion for any amount of liters, but don't have a general formula.

say a car is rated at 10 liters per 100 km, 10l =10/4=gals, 100 km= 100*.
6= 60miles, no problem....60/2.5=24MPG is there a simpler way?

TY
#2
09-24-2007, 10:55 AM
 Robert Fogt Administrator Join Date: Dec 2005 Location: Seattle, WA Posts: 3,467 Rep Power: 13
Re: liter per 100 km to MPG

There is a conversion page available here:
http://www.onlineconversion.com/fuel_consumption.htm
#3
09-24-2007, 08:45 PM
 Roy Nakatsuka Guest Posts: n/a
Re: liter per 100 km to MPG

A simple formula for doing the conversion is:

US MPG = 235 ÷ E
UK MPG = 282 ÷ E

where E is the rating in liters per 100 kilometers. The MPG formulas are different for the United States and United Kingdom, because the UK gallon of 4.546 liters (also known as the Imperial gallon) is about 20% larger than the US gallon of 3.785 liters.

Here's a sample calculation. For a fuel efficiency of 9 liters per 100 km, the conversions are--

US: 235 ÷ 9 = 26 MPG
UK: 282 ÷ 9 = 31 MPG

Here's a table showing the conversions for a number of different values:
Code:
```            |     MPG
L/100 km |   US   UK
-----------+------------
4   |   59   71
6   |   39   47
8   |   29   35
10   |   24   28
12   |   20   24
14   |   17   20
16   |   15   18```
If you're interested, this is how the formulas are derived. Let E be the fuel efficiency in liters per 100 kilometers [L/100 km]. Then

US MPG = 100/E [km/L] x 0.621 [mi/km] x 3.785 [L/US gal] = 235 ÷ E
UK MPG = 100/E [km/L] x 0.621 [mi/km] x 4.546 [L/UK gal] = 282 ÷ E
#4
09-24-2011, 12:19 PM
 Tiger Guest Posts: n/a
Re: liter per 100 km to MPG

These maths conversions are all well and good, but in Europe the fuel consumption is quoted as urban and extra-urban. These European figures involve a drive around a standard course with stop-starts, accelerations and so on. So they attempt to represent real-life driving.
#5
09-25-2011, 01:59 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,535 Rep Power: 19
Re: liter per 100 km to MPG

Quote:
 Originally Posted by Tiger These maths conversions are all well and good, but in Europe the fuel consumption is quoted as urban and extra-urban. These European figures involve a drive around a standard course with stop-starts, accelerations and so on. So they attempt to represent real-life driving.
True, and US mileage is quoted as city and highway, with a specific weighted average between them as the composite. The course profile details of US city and EU urban are slightly different so they are not strictly comparable.

The mathematical conversions above are for units only and assume the same driving profile. Also note the difference in US gallon (3.785411784 L exactly) and UK gallon (4.54609 L) must be considered.
#6
11-26-2011, 03:45 PM
 Tim Albers Guest Posts: n/a
Re: liter per 100 km to MPG

Metric to Imperial. Kms divided by litres X 2.824 will get u really close to mpg imperial.
#7
11-27-2011, 05:26 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,535 Rep Power: 19
Re: liter per 100 km to MPG

Quote:
 Originally Posted by Tim Albers Metric to Imperial. Kms divided by litres X 2.824 will get u really close to mpg imperial.
It will be close, but changing the factor to either 2.8248 or 2.825 will be closer.

The factor comes from dividing 4.54609 L/Imp. gallon by 1.609344 km/mi (both factors exact). To 7 digits, factor is 2.824 809
#8
03-03-2012, 03:41 PM
 Unregistered Guest Posts: n/a
Re: liter per 100 km to MPG

I know this is an old thread, but the standard formula is "282.48/(litres per 100km)"
#9
03-04-2012, 01:44 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,535 Rep Power: 19
Re: liter per 100 km to MPG

Quote:
 Originally Posted by Unregistered I know this is an old thread, but the standard formula is "282.48/(litres per 100km)"
This factor is correct for Imperial gallons. For US gallons use 235.21 instead.
#10
01-16-2013, 10:32 PM
 Euro Guest Posts: n/a
Re: liter per 100 km to MPG

Quote:
 Originally Posted by Tiger These maths conversions are all well and good, but in Europe the fuel consumption is quoted as urban and extra-urban. These European figures involve a drive around a standard course with stop-starts, accelerations and so on. So they attempt to represent real-life driving.
True. But a car always drinks more (sometimes up to 50%) in urban drive than on the highway regardless of units you measure fuel efficiency. So this is completely unrelated to the conversion formula.

What we have here in datasheets is urban, extra urban and, redundantly, "mixed" which - you guessed it - is always middle spot in between the other two figures. Typically the difference urban / extra-urban is given as 25 - 30% which is generally correct.

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