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Author Topic: 55 MPH vs. 65 MPH Back to Topics
AustinLee3

Veteran Author
Tennessee

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Message Posted: Dec 14, 2013 12:58:24 PM

According to different sites, the more you go over 55 miles per hour, the less gas mileage your car will be getting. Does this apply to all vehicles?

I drive a 2003 Cavalier automatic and its estimates get about 21 city to 30 highway. I've been getting 26 city and 32 highway. I've noticed that when I would normally do 55 miles per hour that my car was getting about 30 miles to the gallon, but when I started doing 65 miles per hour on my normal route to school, I've been getting about 32 - 34 miles to the gallon.

To me, it seems as if my car gets better gas mileage when I'm doing 65 miles an hour. Yes, it's wrong and unsafe to speed, but it's just something that I have noticed.
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randy3116
All-Star Author Tennessee

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Message Posted: Apr 16, 2014 5:35:29 AM

unless i excessively speed; my overall ampg remains in the mid-30s
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Houckster
Champion Author Atlanta

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Message Posted: Apr 16, 2014 2:17:43 AM

QUICKIE68 writes: When on trips I check MPG with every tank of gas. I get the same MPG when driving at 65 MPH that I do driving at 80 MPH. Once the car is moving the weight will push the car down the road and get better mileage.
_________
QUICKIE68 has discovered a whole new law of physics.

THE REALITY: The faster a car goes, the more resistance it will meet. THERE IS NO WAY AROUND THIS. The more resistance the car encounters, the harder the engine must work and the more fuel it will consume. THERE IS NO WAY AROUND THIS.

[Edited by: Houckster at 4/16/2014 2:20:34 AM EST]
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pghbill
All-Star Author Pittsburgh

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Message Posted: Apr 16, 2014 12:34:32 AM

forget the 55
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dontuknowOH
Champion Author Ohio

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Message Posted: Apr 15, 2014 11:14:35 PM

Our vehicles get the better mileage at (different for each) speeds when cruising, the engine RPMs are different in top gear, and many other variances in design makes for different economy cruise speeds.
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Quick68
Champion Author Columbus

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Message Posted: Apr 15, 2014 9:08:58 PM

When on trips I check MPG with every tank of gas. I get the same MPG when driving at 65 MPH that I do driving at 80 MPH. Once the car is moving the weight will push the car down the road and get better mileage.
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PatAZ
Champion Author Tucson

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Message Posted: Apr 15, 2014 8:55:29 PM

I go what the speed limit is and don't worry about it.
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cDagasGo
Champion Author Maryland

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Message Posted: Apr 14, 2014 6:35:32 PM

Over 55 seems to get better mileage.
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deant99
Champion Author Ontario

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Message Posted: Apr 13, 2014 9:17:15 PM

65 for me but cruise helps either, except on steep inclines
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dgsteven
Champion Author Los Angeles

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Message Posted: Dec 30, 2013 3:55:37 AM

I prefer 65 mph
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GBMAX
Champion Author Phoenix

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Message Posted: Dec 29, 2013 7:32:56 PM

65 seems best for me
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BartandLisa
Champion Author Newfoundland

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Message Posted: Dec 29, 2013 5:46:32 PM

Depends on the vehicle's engine more than the speed itself.
My car revs at 2500 when cruising at 75mph, while my father's is barely 2000 rpm. At 55 mph, fuel mileage is no better.
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Floridaman2013
Champion Author Atlanta

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Message Posted: Dec 29, 2013 8:51:57 AM

Most automatic transmissions today are 6-9 speeds and with OD. Engines are very fuel efficient so 55 is not an ideal speed for today's vehicles. As other people have pointed out here, there way too many variables that can affect fuel mileage today but going 55 is the least for the newer cars.
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the1roadhog
Champion Author Atlanta

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Message Posted: Dec 29, 2013 8:33:54 AM

Good luck in getting the folk to do 55mph
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cv
Champion Author Raleigh

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Message Posted: Dec 29, 2013 7:12:00 AM

2000 rpms seem to be optimum for my truck and that is 65mph.
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hyeglenn
Champion Author Fresno

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Message Posted: Dec 28, 2013 10:25:28 AM

65 plus.
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Vin63
Champion Author San Bernardino

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Message Posted: Dec 27, 2013 10:22:09 AM

My Duramax is right around 1700 RPM - 65 MPH; the Audi A3 TDI is 1900 RPM - 64 MPH.
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SmoknFord
Champion Author British Columbia

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Message Posted: Dec 26, 2013 11:53:23 AM

Every vehicle has a 'sweet spot', mine is just under 100 kmh. Anything above that then mileage starts to suffer. But... at that speed it makes for boring driving ;)
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the1roadhog
Champion Author Atlanta

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Message Posted: Dec 22, 2013 7:31:16 AM

In '74 it was 55. Don't care to go back to those days.
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kennyman
Champion Author Alberta

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Message Posted: Dec 22, 2013 2:01:33 AM

I don't care. I like the 70MPH speed limit.
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GrumpyCat
Champion Author Alabama

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Message Posted: Dec 22, 2013 1:03:08 AM

Believe my 2000 Avalon got best MPG at 67 MPH. Always got 30+ at 67 or faster. never got more than 27 MPG at 60 MPH.

My 2009 ML320 Bluetec got 31 MPG at 60 MPH over 1000 mile average. But at 70 MPH it gets 29 MPG. Not worth the savings.
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OceanArcher
Champion Author Mississippi

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Message Posted: Dec 21, 2013 11:31:55 AM

Find the best speed for your car, and deal with it ....
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Deno
Champion Author Pittsburgh

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Message Posted: Dec 19, 2013 10:13:54 AM

My old Chevy (05 Impala) gets its best MPG at 62-67 mph, regardless of terrain.
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dontuknowOH
Champion Author Ohio

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Message Posted: Dec 17, 2013 8:32:10 AM

At the time I owned an older car which had a V/8 engine with distributor type older Ign. system. I could attach a timing light and receive the info of knowing at what cruise RPMs the engines timing was advanced the most degrees, rather the light would show the engine's set advance low end RPM timing curve.

The curve changes with varying heavy engine loads on all vehicles old/modern to prevent pinging/knocks/harmful piston/ring/valve damage (plural).

Low end tuning accounts also for pep and fuel consumption, most is done by the ECM, but older engines could be bumped by a good mechanic for each driver habits thus gaining an edge for economy or performance. Emission clamps are in effect today making the engines follow a planned course.
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mojo803
All-Star Author Columbia

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Message Posted: Dec 17, 2013 12:45:02 AM

1600-1800rpm at whatever speed
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nonsuvdriver
All-Star Author Toronto

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Message Posted: Dec 16, 2013 1:51:28 PM

Little better mileage @ 55 but that speed is too slow these days
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randy3116
All-Star Author Tennessee

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Message Posted: Dec 16, 2013 11:23:25 AM

my car averages aout 5% better mpg at 65 than 55
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BobP1950
Sophomore Author Chicago

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Message Posted: Dec 16, 2013 9:38:20 AM

I have a 2009 Ford Focus that i swear gets better mileage at 65-70 mph with the cruse control engaged. Upwards of 35-38mpg.
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ggg452
Champion Author Manitoba

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Message Posted: Dec 16, 2013 9:06:56 AM

Driving slower is not only cheaper but also safer...what's the hurry?
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mincemeat26
Champion Author Atlanta

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Message Posted: Dec 16, 2013 8:50:48 AM

hi
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OceanArcher
Champion Author Mississippi

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Message Posted: Dec 16, 2013 8:47:15 AM

General traffic flow dictates my speed on the highway - except in Texas ...
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Dale Jr.
Champion Author Illinois

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Message Posted: Dec 16, 2013 8:43:35 AM

Wow. I believe everyone here knows the faster you go the less mpg's your vehicle gets.
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twt
Champion Author Virginia Beach

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Message Posted: Dec 16, 2013 6:39:45 AM

What a Nimrod.
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MertieMan
Champion Author Lexington

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Message Posted: Dec 16, 2013 5:17:20 AM

Only a rookie could have thought this up, and the answer is a vehement NO.
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pawnkingfour
Champion Author Georgia

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Message Posted: Dec 15, 2013 10:16:24 PM

I found that to be true, and driving between 45 to no more than 55MPH gives me more mileage per gallon of gasoline.
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Camry05
All-Star Author Indiana

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Message Posted: Dec 15, 2013 7:28:34 PM

65 mph is not speeding in most states interstates and I drive at a "prudent"
speed with the flow of traffic.
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PatAZ
Champion Author Tucson

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Message Posted: Dec 15, 2013 10:34:29 AM

No matter we use the 75mph limit here.
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dontuknowOH
Champion Author Ohio

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Message Posted: Dec 15, 2013 10:33:28 AM

A lot of the difference between 55 - 65 MPH."sweet spots" is due to final gearing plus engine size V/S expected average vehicle weight(planned loaded weight variations)and a big... AND >> the low end Ign. System Engine/cam advance rate timing @ lower RPM Range cruise speeds.

The modern engines automatic control variations is bossed by the ECM System and driver's choice habits somewhat. Then there is the wind direction/force factor and other nature's elements, Many! This planet Yes..... Does grease in a skillet go solid when the heat is turned off? and what if the home A/C is on running? Then what about during Winter when the furnace is running, the grease thing?.... Scrape or pour.....!

Just saying a lot if unseen things affects mileage and automotive type devices 24/7.
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rodmiser
Champion Author Missouri

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Message Posted: Dec 15, 2013 10:19:06 AM

54 mph is even BETTER:)
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Maintroll
Champion Author Lexington

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Message Posted: Dec 15, 2013 8:42:23 AM

This is an old myth since cars now have overdrive and cruise control on them. My car gets better mileage at 70 mph than at 55 mph.
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Glasman
Champion Author South Carolina

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Message Posted: Dec 15, 2013 12:55:53 AM

Amazing-

more rpm's burn more gas-

less rpm's burn less gas-

Merry Christmas !
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AParrette
Sophomore Author Jacksonville

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Message Posted: Dec 14, 2013 10:56:51 PM

i get horrible mileage at 90mph
but that is what I cruise at

i find 65 is better than 55 but that is with my short gearing in my 5spd stick
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forresj
Champion Author Wilmington

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Message Posted: Dec 14, 2013 7:13:10 PM

It's all about air resistance. The resistance goes up exponentially when you increase speed at a constant rate. The sweet spot is usually 50-55mph when resistance is moderate and your engine is engaged at it's highest gear. If you go slower, you'll lose mileage efficiency because your car gear shifts downward eventhough resistance is low below 50mph.

All cars are different on where the sweet spot resides. It depends on the aerodynamics of your car. If your sits low to the ground, the sweet spot is higher than if your car is not aerodynamic. Do an experiment by putting your hand outside the window. You'll experience a much high resistance when your hand is vertical than horizontal.

[Edited by: forresj at 12/14/2013 7:16:31 PM EST]
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minookaband
All-Star Author Illinois

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Message Posted: Dec 14, 2013 5:45:31 PM

every car/truck has a slightly different "sweet spot" for the best mileage.
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Madridjoe
Veteran Author Lancaster

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Message Posted: Dec 14, 2013 5:44:26 PM

I don't worry much about it, just set my cruise control on or slightly above the speed limit, but my Silverado will do better at 55
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hoopitup2000
All-Star Author Virginia

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Message Posted: Dec 14, 2013 5:44:17 PM

Higher speeds=More wind drag

The sweet spot is generally between 40-60 depending on the car.
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rick_evans
Champion Author Boston

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Message Posted: Dec 14, 2013 1:39:39 PM

"but when I started doing 65 miles per hour on my normal route to school, I've been getting about 32 - 34 miles to the gallon."

1. Over what period of time
2. Same road and weather conditions
3. Did you test what happens if you went back to driving 55 to see if it was
not a change in driving style that resulted in the boost in MPG?
4. How did you determine your MPG?
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RickF350
Champion Author Washington

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Message Posted: Dec 14, 2013 1:31:32 PM

My truck gets its best fuel mileage around 45 MPH.
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