even though i personally believe that about 90% of cars get better milage at lower speeds i’ll go off subject and say that, at least where i live, if you don’t hit the gas and fly down the high way your going to get rear ended by a semi truck. again ti may be differnt where you live
I stick with my comments that some vehicles will get better mileage at higher speeds.
Also, I’m close to anal about things like this and it’s ludicrous to think that I would be driving in 3rd and not know it.
For those not in the know, my Lincoln Mark does NOT EVEN HAVE 2 DRIVE positions on the shifter. It only has one DRIVE position. Overdrive is turned off by a button and when turned off, the rpms go up and a green “OD OFF” lamp illuminates.
And it ain’t happenin’ judging by the 1800 rpm at 70 mph cruise.
Anyone want to comment on the mileage in regards to my old BMW motorcycle?
An R/100/7 and in 5th gear at 55 it gets 30-32 and at 70+ it gets better than 40; and yes, it’s still in 5th gear.
And that has been verified a number of times including several near 2000 mile cross-country trips with a near 5 gallon gas tank.
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Checking fuel mileage over one tank can be erroneous if you do not fill to the same level at the same station at the same pump. Filling technique is vital.
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Get on your bicycle and go slowly and then fast. Then decide which speed requires more effort. Those of you who can go fast more easily than slowly will also get better gas mileage going faster with a car.
On #2, of course it takes more effort!!! But you’re covering more ground in less time so it may actually be more efficient. The computation for efficiency has three inputs; energy consumed, distance traveled and time elapsed. Why not try your experiment with the bike in first gear and see how good you do. Better yet, put it in the highest gear and don’t pedal very fast. Did you use more or less energy to travel the same distance? Was inertia your friend on the hills?
#1 will never work on a single tankful. It’s far too inaccurate. You have to AVERAGE fuel consumption over many tankfuls to get any meaningful information.
The notion of getting better mileage in any car by going faster is absurd. The ‘sweet spot’ is in your head.
If it’s absurd then explain how I got my aforementioned results posted on the first page of this discussion? I arrived on the mileage estimates over many tankfulls of fuel - filling up every other day for about 6 months. I also kept immaculate records of fuel and mileage, coming up with the averages.
And someone mentioned time elapsed. Fact is, when one drives faster, the engine runs for less time because you reach your destination faster. Really, the difference in mpg using fuel as the constant is minor by speeding up. However, if one arrives at a destination half and hour earlier, that half hour the engine isn’t running more than makes up for the reduction in mileage at speed. Therefore, in the real world, it would end up you would get better mileage by driving faster, due to the engine running time reduction.
It’s a God given fact, believe it or not. Where did I say that every car or motorcycle would get better mileage at higher speeds?
I SAID that some will; it depends on a number of factors including gear ratios and what not.
I have been waiting to see if anyone is going to mention something that affects this, but so far no one has. You’re the anonymous expert; want to give it a stab?
Give it up, you’re either arguing with a troll or someone who has no basis in mechanics from which to draw their conclusions.
I won’t give it up. My figuring is done on countless tanks of gasoline. I also live in a rural area and 99% of my driving is on the open road; about half on 55 mph county highways and the other half on state 65-70 mph roadways.
If it’s 10 o’clock at night and I want a cold brew then it’s a 50 mile round trip to get one.
It appears that a question I posed was flagged for some reason and is now gone.
So here I go again.
There may a reason why the situation as I describe it (better economy at higher speeds) could occur. Does anyone want to take a stab at it? It’s not that transparent a possibility if one is a “mechanical thinker”. 
The notion that driving faster always consumes more fuel is false.
The above is tgrue only on completely flat roads with no wind.
If are in high gear you go as slow as you can go before the engine lugs on a flat road with no headwind, you will get great mileage. But you will not necessarily be in the best torque range. Start going up a hill and you will waste gas. Rev up to a better spot in the torque range before you climb, and you will get better mileage on the hill.
Each car has different torque curves and gearing, so YOUR MILEAGE MAY VARY. I know that in hilly terrain, my 1985 Honda Accord got 3-5 more MPG at 65-70 than 55.
Look at the research for Continuously Variable Transmissions (CVT’s). The idea there is to keep the engine in the ‘sweet spot’. So I buy into the sweet spot theory.
To Tom in Sacramento: It’s not just the money saved, it’s the potential reduced dependance on foreign oil, and the lives saved if everyone drove like a person with a brain rather than like a madman. Yes, it’s worth it.
Charles in Phoenix
NOBODY has the patience to drive 55 mph for any length of time on any interstate near Colorado. That’s 85 mph country. You would get a ticket for obstructing traffic. Your 2.73 gears would indeed produce the lowest possible RPM. My '92 Vic gets better mileage than my Mother-in-laws '95 4cyl Escort…(22mpg)…Hard to believe, but true…
I think that you need to do the exact same trip at the different speeds. It would be OK to drive one way at lower speed and return on the same road at the higher speed. The test would be valid of you had similar traffic conditions.
I did this with a rental Impala. I drove one direction at 60 MPH and the other at 70 MPH with the cruise control on. I got 15% better mileage at 60 MPH.
I think you may be able to add a vacuum gauge to your intake manifold to find the best speed for good mileage.
From: Tom Keys
At: tomandgail1@tx.rr.comGasoline mileage
This is in reply to your story in the
Dallas Morning News, Sunday, July 15,
Automotive Section, Page 1M, “How high will
gas go before we slow down.” Now if you
wish to reprint this and make it more
concise, you have my permission. I am 75
and normally not a hot rodder. During Sept
and October of 2006, my wife and I took a
70 MPH and 75 MPH , driving trip from
Dallas up through Okla, Kansas, Nebraska,
Wyoming, Montana and into ALberta, Canada
to Lake Louise and on up to Jasper and back
to Dallas with a side trip to Calgary and
then down through the Rocky Mountain
National Park. This was a 4 week trip in
our 2005 Acura 6 CYL. MDX SUV loaded up
with both summer and winter clothes plus a
plug in refrigerator. This vehicle is
designed in California and manufactured in
Canada and MUST use high test gas only (at
$4.00 a gallon in Canada in 2006.
Consistantly,ALWAYS, we received 23 MPG
with a loaded vehicle and always driving
through the Great Plains and north at 70 to
75. We always checked our odometer while
gassing up and also used our pocket
calculator. NOTE> We also had to keep
close track converting Canadian liters into
American gallons ( not Imperial gallons)at
the pump and kilometers into miles as the
speed limit in Canada is STILL about 50-55
MPH in most cases which really sucks. Our
gas mileage ran a consistant poor 17-18
Miles per galloon when maintaining that
required lower speed. Once we were able to
head east across Canada toward Calgary at
max speed we again regained our 23 MPG and
again south through the Great Plains. While
driving through the Colorado Rockies and
again at reduced speed, we again dropped to
17 and 18 MPG. Bear in mind also, that all
the Montana highways are over 7000 feet in
altitude and into Canada and the thinner
air still delivered 23 MPG. So, in this
specific case, I dispute your claim.
Sincerely, Tom Keys, Carrollton, Texas.
Here’s the rest of the story for Frank, who wants to endanger us all by increasing the speed delta on highways. At 75mph his 300mi trip would use 8.7gal (@ 44.5-10=34.5mpg). That’s 2gal more but 1hr less. So he’s earning $6/hr. Is that worth it?
Slowing down means that he saves $6 in return for spending an extra hour on the road. That’s not even minimum wage!
I understand the mpg issue when driving
slower and I have no problem with it. I was
wondering where the additional running time
comes in? If one drives 1000 miles at 60
mph vs. 75 mph that means the vehicle is
running about 2.4 hours longer on each 1000
mile trip. If you drive at that rate for
100K that means another 240 hours running
time if my math is correct. That’s 10 extra
days my vehicle has run. I was wondering
where that fits in the equation?
When driving slower you use enough less fuel per mile AND per unit of time so you use less fuel for the total trip even if it is stretched over more time.
I remember when I was about 10 yeas old my older brother and my father were talking about running out of gas and I suggested going faster. It was a while and some laughter before they explained that fact of life.
[b]The notion that driving faster always consumes more fuel is false.
It all depends on the car, the engine, gear ratios, etc.
My Lincoln will get better fuel economy at 70 than it will at 55; all proven during a number of road trips.
[/b]
Extremely unlikely. I suggest poor testing and wishful thinking. The one very important factor is wind resistance which increases with speed faster than 1:1.