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Can't figure this !!!!! I drove to Reno when my Suby had 500 miles on the odometer and got fantastic mileage. 33 going 34 returing. Evervbody else was reporting mileage in the 28 range. Just turned 3500 on the odometer and drove to BC last week..a 1000 miles R/T. Mileage dropped to a steady 28 the whole trip. On both trips the trip MPG reading was extremely accurate....reading the same MPG as I was calculating. Only thing different was during the first trip I never exceeded 60 mph. On the BC trip I was running 70-75. Does speed really have that kind of effect?
 

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I need a fog horn, ,
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short answer: yep.

long answer: your gas mileage is inversely affected by your cruising speed- the faster you go the more gas you have to use to maintain that speed. faster means: more friction on the tires from the road- more friction from components moving faster (AC, PS, etc), and most importantly- more friction of the air against your car. all these things are conspiring to slow you down, therefore you have to use that much more gas to maintain a constant speed.

So you get 5mph better cruising at 60 than 75ish, you might find you gain 10mpg cruising at 50 rather than 75ish- but who wants to set the cruise control at 50?
 

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Yes, speed is a major contributing factor in MPG. I remember once I read somewhere that anything over a certain MPH, say 55 MPH, you lose 2-5% MPG per 3-5 MPH faster. Some odd general calculation like that. Or was that just the Government justifying tickets for speeding................
Brian
 

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I have the same car as you do and the only long trip we hav taken so far was when there was 2500 miles on the odo. I averaged 31.5 there and 30.5 on the way back. 350 miles each way going I was averaging just under 70mph on the way back averaging 75. In my wifes daily commute 35 miles each way about 60% on the freeway going 65mph and 40% in stop and go traffic she averages right at 27.5mpg per tank. Car has just over 6000 miles on it now.
 

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bheinz57 said:
I remember once I read somewhere that anything over a certain MPH, say 55 MPH, you lose 2-5% MPG per 3-5 MPH faster.
Seems like I heard that air resistance for most vehicles causes plenty of MPG loss once you are moving above about 40 MPH. Probably one of those exponential things, too, instead of linear.
 
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