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Old Dec 8, 2005 | 07:55 PM
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Question 55mph marks?

Why is 55MPH marked on virtually every older vehicle I see? Nothing that really changes at 55MPH. Anyone know by some chance? Just curious. Thanks.
Zach
 
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Old Dec 8, 2005 | 08:04 PM
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I always thought it was because of the common highway speed limit of 55 mph.
 
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Old Dec 8, 2005 | 08:19 PM
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What n578md said. Newer cars don't have it because the speed limit now varies from state to state, when it used to be 55 mph across the board, from the time of the gas crunch in the 70s to sometime in the early 90s or late 80s when that federal regulation was changed to 65 and later left to the states.

Jason
 
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Old Dec 8, 2005 | 08:37 PM
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Although I agree that the national speed limit was probably the reason they were marked at first, the marks didn't die with the double-nickle. My grandmother has a '99 Explorer with a (faint) mark at 55. I assume that the mark is put there because that is a fairly efficient speed at which to operate the vehicle. Fuel mileage starts dropping fast past 55, anyway. (I think, in an auto, best mileage is usually around 45, right after the TC locks up.)
 
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Old Dec 8, 2005 | 08:58 PM
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The 55mph mark, to me means the optimal crusing speed for economy. and it generally means the norm around here for speed limits too.
 
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Old Dec 8, 2005 | 09:01 PM
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Yeah I know 55mph is the "best" speed for economy cruising the majority of the time, or rather close to it.

Now that I know the former highway speed limits were 55mph, that explains.

2000 must have been the year they stopped doing it. Our 2000 Silverado has no mark at any speed, neither does the 2003 Yukon or 2002 F-250, so I figure it's safe to say that was the "cutoff" year of sorts for the manufactureres.
 
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Old Dec 8, 2005 | 09:33 PM
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Prior to the 55 speed limit, it was 65 back in the mid sixties; here in Ca.
 
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Old Dec 8, 2005 | 09:45 PM
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Dang I feel OLD.
 
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Old Dec 8, 2005 | 10:13 PM
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My 1987 Ford 8000 tandem axle grain truck has this 55 mph mark highlighted with a circle as well. To argue that it is the optimum fuel milage mark is hard. As the 3208 Cat and 13 spd Fuller acheive about 2300 rpm, 200 rpm short of maximum recomended engine speed. Hardly optimum fuel milage.
 
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Old Dec 8, 2005 | 10:44 PM
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I think they meant 55 as being optimum for your standard passanger vehicle and truck.
 
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Old Dec 8, 2005 | 10:51 PM
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I don't know about that at all. My '92 E150 got ~17mpg at 70mph and 13 to 14 at 55mph. Then again it was only turning 1500 rpms at 55, and 1900 at 70.
 
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Old Dec 8, 2005 | 10:59 PM
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Hmmm! I used to get 17 mpg at 70 and 20 mpg at 55 in my 81 F150.

I guess it depends on the vehicle and other variables.
 
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Old Dec 9, 2005 | 01:17 AM
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Definitely. My Thunderbird gets the best mileage between 70 and 80. I've always wondered about the 4 mysterious dots on my Tbird speedometer. Any truck owners out there with mysterious dots?
 
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Old Dec 9, 2005 | 01:53 AM
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Yeah I have some of those dots on my Bronco too...there's one at abut 58mph and one at about 62mph. Strange.

55 should be a pretty economical speed, which, as others have mentioned, is why it was the speed limit and why it was marked.
 
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Old Dec 9, 2005 | 10:10 AM
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Some cars/trucks without tachometers had dots on the speedometer to indicate max speed in each gear. It was a trick I used back in the 50's before I could afford my first Sun Tachometer. LOL Also all cars in the 70's and early 80's I believe had government mandated speedometers with a max speed reading of 85 MPH. The theory in Washing DC at the time was if you were going more than half the max speed on the speedometer you wouldn't be tempted to speed. Didn't work. I know a lot of guys that wanted to see if they could "bury" the speedometer. LOL
 

Last edited by MemphisSenior; Dec 9, 2005 at 10:17 AM.
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