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pawoSD · #6 07-28-2009, 02:48 PM

Quote:

Originally Posted by BobK

depends on a bunch of factors. What car, what road, what wind direction and speed, how much stop and go, what tire inflation? During the 55 years, it was figured they could have saved more gas if they had keep the speed limit at 70 and mandated 4 more psi in all tires. My SDL got better mpg at 75-80. Found that out when I was making almost daily 200 mile round trips when mom was sick. Went from 23 to 27 mpg. My old '74 Datsun 260Z barely got 20mpg at 55, but got 26.5 at 85mph. Whole lotta factors involved...but that doesn't fit in the safety nazi or car haters agenda.

That would be impossible to get 6.5 more mpgs going 30mph faster....that defies pretty much every law of energy and physics.

In my diesel I have seen the ultimate best mileage going 50-55mph and coasting all the way to stops (as little brake usage as possible) and gentle steady accelerations. I've seen as high as 30.4 in my 300SD.....my W124 can go a bit faster and still get optimum mileage, it seems to peak around 68-72mph.....on cruise control with no headwind and no A/C on....I can get around 26. Usually its around 22-23 though. The diesel gets about 23-24 at 73mph.

However, there are no cars that will get 6+ mpg higher going 85 than if they were going 55. Not possible. Wind resistance goes up dramatically as well as tire rolling resistance and everything else.