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Old 05-28-2007, 05:29 PM   #15
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Join Date: Dec 2002
Location: Ottawa
Posts: 4,006
Originally Posted by BigD
Cool, I have been misinformed (edit: what load do they use though, that is the key. You can't measure how much you car will have to work in the real world on a dyno, when air resistance builds up exponentially, and not all roads are flat, plus I bet they accelerate slowly - well used to, that's why the 'adjusted' rates are much lower). Do you actually figure your consumption with real numbers?
The numbers I get personally are actual calculated numbers, the OBC is quite optimistic. If I go by it, It tells me I'm getting 7.9 L/100km or less on pure highway.

For the EPA and Canadian highway tests they use 'conversions' to account for wind resistance based on drag coefficient and frontal area. etc.

I heard a while back that they were going to add a 3rd test that would simulate 'higher speed' driving (100km/h +) and they would put that as a seperate rating for new vehicles, but I have yet to see them begin doing this.

How do you account for independent tests though, who consistently get worse mileage than EPA and as I noted above, the 540i6 is no exception, with MT averaging 18.
I dunno, I can't really. Really there are just too many factors that could change the millage significantly. Like Elevation, temperature, gears, different drivers etc. It would be too hard for me to speculate why there are such varriances.
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