does anyone know....
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Joined: Sep 2005
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From: Springfield MO
does anyone know....
I was wondering at what speed do you get the best mpg, I have searched for charts but couldn't find any. I have heard it is about 55-65mph??
Last edited by samson80; Oct 6, 2005 at 10:14 AM.
Instructor
Joined: Jun 2003
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From: Halethorpe MD
It depends on your gearing. It is more of a matter of at what RPM in your top gear do you get the best mielage. I may be wrong but I believe it is the RPM at which your engine pulls the most vacuum because old style fuel mileage gauges were just vacuum gauges.
Melting Slicks
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St. Jude Donor '03,'11
Originally Posted by samson80
I was wondering at what speed do you get the best mpg, I have searched for charts but couldn't find any. I have heard it is about 55-65mph??
many years ago i had one of those computers in my car that monitored real time fuel consumption and speed yada yada yada.
i got the best instantenous MPG at around 40 mph. Somewhere in the 20s if i remember right.
All these dudes getting mid 20's MPG in their C3 must have been taught to drive by their grandmothers.
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Joined: Sep 2005
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From: Springfield MO
Originally Posted by turtlevette
many years ago i had one of those computers in my car that monitored real time fuel consumption and speed yada yada yada.
i got the best instantenous MPG at around 40 mph. Somewhere in the 20s if i remember right.
All these dudes getting mid 20's MPG in their C3 must have been taught to drive by their grandmothers.
i got the best instantenous MPG at around 40 mph. Somewhere in the 20s if i remember right.
All these dudes getting mid 20's MPG in their C3 must have been taught to drive by their grandmothers.
Last edited by samson80; Oct 6, 2005 at 10:26 AM.
Le Mans Master
Joined: Mar 2004
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From: Little Rock AR
I think you should theoreticaly get the best mileage when you have the highest brake specific fuel consumption. 
That would have the highest thermal efficiency.
Highest Vacuum probably optimizes highest volumetric efficency (a component of overall thermal efficency) and that is a good thing but probably not the exact point of maximum fuel efficency but I am just shooting from the hip here.
Obviously this optimal speed will vary depending on cam timing, gearing, wind resistance, etc. Every car is different especialy if it is modified from stock. Is that a screwy statement or what?
-Mark.
That would have the highest thermal efficiency.Highest Vacuum probably optimizes highest volumetric efficency (a component of overall thermal efficency) and that is a good thing but probably not the exact point of maximum fuel efficency but I am just shooting from the hip here.
Obviously this optimal speed will vary depending on cam timing, gearing, wind resistance, etc. Every car is different especialy if it is modified from stock. Is that a screwy statement or what?
-Mark.
Team Owner
Joined: Jul 2004
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From: South West - but north of Dayton, Ohio
If I'm driving my Vette - I could care less about mpg. It sucks gas at about 12 mpg average. I can tell you that the harder you stand on it - the worse your mileage will be... 
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Drifting
Joined: Dec 2004
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Originally Posted by turtlevette
many years ago i had one of those computers in my car that monitored real time fuel consumption and speed yada yada yada.
i got the best instantenous MPG at around 40 mph. Somewhere in the 20s if i remember right.
All these dudes getting mid 20's MPG in their C3 must have been taught to drive by their grandmothers.
i got the best instantenous MPG at around 40 mph. Somewhere in the 20s if i remember right.
All these dudes getting mid 20's MPG in their C3 must have been taught to drive by their grandmothers.
While I've never driven slow enough to find out, generally, you need to be in high gear at the lowest road speed that the engine runs smoothly. Mileage is related to engine efficiency and wind resistance, and unless you have a radical cam, low revs (minimum internal friction) and low speed (minimum external load) will give the best mileage.
Sticks do better since they waste no energy pumping oil, have NO gear losses (on 4 speeds w/1:1 top gears), and have no slipping torque converters or disengaged, but still dragging (wet internal) clutches or brakes.
OD autos make up for some auto losses by running the engine slower, but the engine still needs the same power to keep the car moving as a direct drive auto at any given speed.
Melting Slicks
Joined: May 2005
Posts: 2,152
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From: Folsom Ca
Originally Posted by samson80
Thanks for the help I guess that it is diffrent in every car, I will just have to do a few experiments myself! 
Drifting
Joined: May 2004
Posts: 1,442
Likes: 2
From: Flanders NJ
Originally Posted by samson80
I was wondering at what speed do you get the best mpg, I have searched for charts but couldn't find any. I have heard it is about 55-65mph??
Sorry, coun't resist
Team Owner
Joined: Feb 2005
Posts: 32,519
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From: central America
St. Jude Donor '08-'09
Originally Posted by 71redskin
i'm no expert but i always thought a car ran its most efficiently at halfway the redline on the tach...so if your redline was 6k...3k would get you the best mileage...just my .02
trw