Most fuel efficient speed to drive?

Page 1 of 2  
Back in the 80's I remember my dad telling me that the most fuel efficient speed to drive his car was at 45 mph, and that it was a spec that was published for many car models.
With the gas price absurdity these days, I'm just curious if is there an equivalent most efficient speed for today's cars? (Specifically my 05 EX-4 accord)
-MVL
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

;-) Greg
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Coupla anecdotes to throw into the mill:
My 1991 Civic seems to get its best fuel mileage somewhere between 35 and 55 mph.
Someone recently posted here that going over 3000 RPM reduced mileage. That figure may vary somewhat, but I have noticed that cruising at 70 mph in 5th gear (of course) with my car puts me over 3000 rpm and reduces my fuel mileage. I do not get my best mileage on long highway trips, with the cruise control set at 68 mph.
Avoid rapid accelerations.
It seems staying in gear (instead of coasting with the engine at idle) and braking with the engine improves my Honda's fuel mileage, too, because (according to someone here) of the way the fuel control etc. system is set up.

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 30 Aug 2005 02:56:50 GMT, "Elle"

For every carburated car i've owned, the optimal speed is around 60mph. This is, i believe, why the US speed limits were set to 55 in the oil crisis.

depends on the hill, and what you do with the coasted momentum really - use it to boost your vehicles speed, and you culd save fuel.
Never really bothered to be honest, since fuels so cheap in the US.

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

That was one reason. 55mph was determined in tests to be a good compromise between speed and mileage. The cops loved it too, once they discovered they could make megabucks from all those new scofflaws driving on roads designed for much higher speeds than 55. Hello, Fuzzbuster!
The other reason was the new pellet-type catalytic converters that were mandated for 1975. It seems that they had a tendency to fire pellets out the tailpipe if exhaust pulses got too violent. No pellets = no conversion. Modern monobloc cats are immume to this.
<snip>

It sure is (thank god). http://www.aip.com.au/pricing/oecd.htm
I've also not found much difference in my mileage with car speed. Not enough to make me do anything about it, anyway.
On average, I get about 27 mpg. A low of about 25 is seen at sustained sppeds over 90 mph, and a high of about 30 at sustained speeds of about 60mph. I only conducted my speed tests once (60 is boring, 90 is too cop- friendly), so I can't confirm my results.
--
TeGGeR®

The Unofficial Honda/Acura FAQ
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Dunno. My 91 Civic is fuel-injected.

We disagree.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Agghhhh ... not this conversation again!? ;p

Grrrrrrrrrr .....
a
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That's because the fuel only cuts out (some carburetors too) when in gear and above 1180-rpm and gas pedal released (carburetor rpm is different). Idling is big business. Cruising is only a fraction of the injection pulse width if you measure it. Your best bet is to keep moving (not to slow, not too fast) in gear to increase your miles per gallon.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Instead of speed watch the RPM. The sweet spot for most Hondas are from 2100 to 2400 rpm. Since some people may be driving on the wrong gear at 55-mph.
The new VTEC-E has a different higher sweet spot. Check your information source.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 29 Aug 2005 18:34:38 -0700, mvl_groups snipped-for-privacy@yahoo.com wrote:

Wind resistance is another factor that has not been discussed so far. The relationship between wind resistance and speed is complex. However, at low speeds, the amount of wind resistance depends linearly on speed. For example, is the speed of the car is increased form 20 mph to 40 mph, the wind resistance. will roughly double. However, at higher speeds, the wind resistance will begin to increase more sharply, so that doubling the speed may triple or quadruple the wind resistance.
Part of the reason the spped was set to 55 was because with cars back then, that was the approximate speed at which wind resistance began to be an important factor. This became obvious if one listened to wind noise. At 45 or 50 mph in my 1976 station wagon, wind noise was barely noticeable. But at 75, conversation became difficult.
Modern cars are much more aerodynamic than they were 30 years ago (except for those Chrysler products with huge, boxy, ugly grills), so the wind resistance probably does not become an important factor until a higher speed, but at some point it is going to take much of the available engine power to just keep the car moving.
Elliot Richmond Freelance Science Writer and Editor
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Wind resistance (as measured by power required to overcome aerodynamic friction) should vary roughly in a square or cubic relationship with speed.

I suspect what's really at work here are the conditions under which your typical car engine is designed to operate most efficiently. That the typical passenger car is not designed for optimal efficiency at 20 mph nor 75 mph makes sense, since the average driver's average cruising speed is probably closer to 35 to 60 mph.

I wouldn't use the decibel level to indicate anything more than wind resistance goes up with speed according to a square or cubic relationship.
(I lean towards cubic, from a units analysis standpoint, but I may be missing something from empirical studies on car drag.)

All engine power is strictly to keep the car moving. "A body in motion tends to stay in motion, unless [the nasty F-phenomenon kicks in, which it will]."
We can't eliminate engine (internals), wind, or rolling friction.

Free.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sounds rather low. I would have thought 55-65mph a sensible speed in 5th, though quite how anyone can set cruise control (or even use it for that matter!) at that low a speed on a motorway is quite beyond me!

Give it a break! You guys are pretty much *given* petrol. At least this is a Honda group, so most of you aren't as selfish as your fellow countrymen in their gas-guzzlin' 4x4 pieces of crap. Try paying £60 to fill your tank each time (over $100).
a
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not if it had poor aerodynamics, which would have been pretty common back then (especially if the car involved was not brand-new in the '80's but a car 5 years old, maybe dating from the mid-'70's, even). At low speeds, aerodynamic drag will be unimportant but it increases with the square of the speed.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
mvl_groups snipped-for-privacy@yahoo.com wrote:

level ground 45 to 50mph in 5th gear sounds about right(off the top of my head) and probably puts out about 2200 RPM. Anything below 1800 RPM starts to labor the engine. Above 65 mph much of your fuel is consumed pushing air out of the way of the car. All experts & mechanics(I am neither) out there, please correct me if I am mistaken. Rich
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
mvl_groups snipped-for-privacy@yahoo.com wrote:

This question was printed in the latest Road & Track magazine... there's a very good, extensive answer there (check out the issue with the "flat-out one-mile" tests on the cover).
--
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 0535-3, 09/02/2005
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
mvl_groups snipped-for-privacy@yahoo.com wrote:

Actually, you can also find the R&T article here: http://www.roadandtrack.com/article.asp?section_id &article_id%90&page_number=2
--
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 0535-3, 09/02/2005
  Click to see the full signature.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
if i drive 70-90km/hr in my 04 civic (automatic tranny) i usually get 50-55 mpg consistantly
On 29 Aug 2005 18:34:38 -0700, mvl_groups snipped-for-privacy@yahoo.com wrote:

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
yeah, canadians sorta use a combination of the 2 systems. or at least i do. :)
On Sun, 04 Sep 2005 03:50:49 GMT, "Doug McCrary"

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I communte through many stop lights and stop signs each day. I've been looking for the most fuel efficient acceleration for my 05 Accord (4 cyl).
I've seen posts saying that cars in general drive most efficiently if driven near peak torque RPM, which for the accord is around 4500. My car's an auto, so I don't have too much control over RPM's. But the automatic likes to hover around 2000 RPMs, so the only way to be close to 4500 is almost flooring the starts.
But I've also heard that the harder starts are less fuel efficient. Based on the Nav MPG, I think I've found keeping RPM's under 2000 (sloooow acceleration) is more efficient.
I don't mind speed of acceleration, since my commute is on 1-lane roads where no one can pass, and regardless of how fast I drive, I just get stuck behind another car at the next stop light.
Anyone able to comment one way or the other on hard vs. soft acceleration?
-MVL
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.