Being overseas, my current and previous cars invariably express their parsimony via the computer as litres consumed per 100km driven.  Is there a simple formula for recalculating fuel consumption into mpg?  I get there eventually but I tie myself in knots, first converting the litres into gallons, then calculating how many gallons I've used over 62 miles... etc. 
 
And is 8.6l/100km a decent figure for a BMW 335D?!  TIA.
                            
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                        I use 62.5/L*4.546 where L is your litres/100km figure. 
 
So in your case, it is 62.5/8.6*4.546 which gives 33mpg.
                            
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                        Perhaps a table - 1 mile per gallon = 286 litres per 100 km, as the former doubles the latter halves, so: 
 
1 mpg = 286 l/100km  
2 mpg = 143 l/100km  
4 mpg = 72 l/100km  
8 mpg = 36 l/100km  
16 mpg = 18 l/100km  
24 mpg = 12 l/100km 
32 mpg = 9 l/100km  
48 mpg = 6 l/100km 
64 mpg = 4.5 l/100km 
                            
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                        Always use Microsoft Calculator Plus: 
 
preview.tinyurl.com/4lxa3 
 
In a classic case of Hutber's Law, the "new improved" calculator in Windows 7 doesn't appear to include the consumption conversions!
                            
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                        From someone who did proper "O" level maths 
Devide 272 ( he thinks) by the litre per 100km fig 
= mpg 
simples 
                            
                                Edited by dieseldogg on 15/11/2009 at 10:48
                             
                            
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                        >>From someone who did proper "O" level mathsDevide 272 ( he thinks) by the litre per 100km fig = mpg simples  
 
 
The figure is 286 as per my table above.
                            
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                        The magic number is actually  454.6 / 1.6093 , which comes to 282.5 . 
 
And it works both ways. Divide this number by mpg to get litres/100km ; or the reverse.
                            
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                        My ... cars invariably express their parsimony via the computer as litres consumed per 100km driven  
 
British cars have a switchable option.  Doesn't yours, or do continental models extend their parsimony as far as that?
                            
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                        Use www.onlineconversion.com 
 
Converts lots of other things too!
                            
                                Edited by Mchenry on 15/11/2009 at 13:11
                             
                            
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                        Ok its a while since I worked it out , I was aware that the 272 fig was perhaps not correct. 
cheers 
M 
                            
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