Re: DRLs

[John Hobson <johnh@haht.com>]

>> I have to agree. I can't believe that ANY lights would have a measurable
>> impact on mileage. Even A/C is far less than a 10% drag... Since an
>> alternator is being belt driven all the time anyway (unlike a clutch 
>> operated A/C unit), how would the mechanics of lower mileage come into
>> play ?

The greater the electrical load on the alternator, the harder it is to turn
the alternator. For example, a hand-crank generator would turn freely with
no load. But if the generator is under load (say powering a set of lights),
then the generator will be harder to turn.

DRLs should not drop mileage by 10%. It should possible to estimate the drop
in mileage. Use the wattage of the DRLs to determine how many kilowatts per
hour the DRLs are using. Convert the energy in a gallon of gasoline to
kilowatt hours. Now divide the kilowatt-hours DRLs use by the number of
kilowatts in a gallon of gasoline and multiply by 3 (if you assume that an
internal combustion engine is 33% efficient) to get the amount of gasoline
used per hour by DRLs.