Is going 55 mph really the best speed?

[schume]

Originally Posted by BEEF

looking at it strictly scientifically

I have seen graphs on aerodynamic drag that show there is a deflection point where drag increases sharply. the sharp increase is usually between 50 and 60 mph depending on the aerodynamics of the particular vehicle. I know I saw one that showed the optimum for a vehicle being 53MPH. I can't remember what vehicle was tested but I do remember it being old.

that may be where the whole 55MPH thing came from. it gives you the most speed for the least amount of drag.

there again, I may be reading way too much into the question.

When I worked in HVAC, I came across fan law which can be translated to cars. http://www.hvac-toolbox.com/fan-affi...aws-d_196.html

Aerodynamic drag and engine power needed changes exponentially with an increase in speed. That's why you can't regear a stock Yaris and go 200mph or use hypermiling techniques doing 90. (and expect anything good)

Speed kills.... fuel economy at least :)

[tire]

Originally Posted by thebarber

you want the lowest speed in the highest gear...

this is correct, for any motor vehicle. anything short of bogging the motor will be ideal for fuel economy.

[joe keeney]

55 you'll get flatten by a pick up down here,

[PROX4x4]

I got 45.1 Doing 55-60 MPH, no cruise control.

[joe keeney]

55 not in texas you'll be a hood ornament on a pick up,

[charles nelson]

I average consistently mid-40s mpg while driving at 50 mph.
If there is no wind, the Yaris gets about 50 mpg at 50 mph. Mileage drops to about 40 mpg at 70 mph. At 30 mph I get high 50's mpg.
With a strong head wind I loose about 10 mpg.

[Ilovemyyaris]

I go about 55 plus or minus all the time. I generally get at least 40 or more mpg. Normally about 45 - 50 mpg if it's just highway.

People hate me for it though. Sometimes people honk, middle fingers, angry red necks shouting out the window, and etc. Not sure what's so hard about using the other lane for to pass. I've even seen some other people driving the Yaris wizz past me. Am I the only person who lives in GA who knows about this?

Sometimes I follow big rigs if I need to get somewhere faster. I don't do that much because I heard it's dangerous. Just wondering. Anyone know why exactly they say it's dangerous? As long as you're not right up on them. Doesn't it take them a lot longer to come to a stop than a small car?

[rningonfumes]

Well along with the stopping issues, trucks tend to kick up things real easily and there is also the possibility of a tire blow out. I see what you mean about the stopping but the latter two is what keeps me from drafting, that and truckers hate it.

LoL, at certain times while on the highway some truckers think I'm drafting them so they slow down to 55 or even 50 to try to shake me off. They don't realize I don't want to speed up.

One other point is that sometimes there is debris on the road that is nothing for a truck to run over but it might be too large for your car to handle. So if you are drafting you won't see this object and will not have time to avoid it.

[badmofo]

I drive the speed limit (60) to and from work, 70 miles total, all highway. I don't draft, I coast downhills, I use DFCO down steeper hills and when coming to a stop, Accelerate slowly. I've found it's not one thing you do to increase fuel mileage but a combination that gives the best results.

[Cosworth]

i haven't found a magic speed that would allow me the highest mileage... having said that I get better mileage when I drive between 55-63mph in 5th gear. At this range, I get anywhere from 45-55 instant mpg according to ecometer. At 70mph, I usually get at least 41mpg on average.

[marcus]

47 mpg going 90 kph ; 55 mph 90% of the time fully loaded with a/c

[caineroad]

Originally Posted by marcus

47 mpg going 90 kph ; 55 mph 90% of the time fully loaded with a/c

there must be something wrong with your mpg meter or your calculation.

better yet tell us how many km or miles you can do in a full tank of gas.

im in canada, in my yaris full tank of gas 600km is pretty much top highway driving. That equals 41-42 US mpg

unless you can cover 800km in a full tank, how is 55 US mpg possible?


But conversion from 42 US mpg = 50 UK mpg are you referring to uk units?

[rningonfumes]

^ This year I've hit 522.9 (841.5km) miles on 9.877 Gallons. I've hit the magic 500 a couple more times this summer season.

55mph/no drafting(truckers usually are faster)/lots of highway/I like the down hills (you infer what you want).

If I'm alone, no A/C ever- just 1 inch down on both front windows. If I have passengers, I make them comfortable- only complaints I get is I drive too slow. Even my parents tell me to drive faster if they are the passengers.

[caineroad]

Originally Posted by rningonfumes

^ This year I've hit 522.9 (841.5km) miles on 9.877 Gallons. I've hit the magic 500 a couple more times this summer season.

55mph/no drafting(truckers usually are faster)/lots of highway/I like the down hills (you infer what you want).

If I'm alone, no A/C ever- just 1 inch down on both front windows. If I have passengers, I make them comfortable- only complaints I get is I drive too slow. Even my parents tell me to drive faster if they are the passengers.

841km wow.... impressive

manual tranny works better?

[rningonfumes]

Well, I like my 5speed. You don't have to have a manual for the mpg but it helps. There are people on YW who hit 50mpg quite readily who happen to have autos. What this means is it requires patience. The right weather does wonders as well.

[caineroad]

Say if we are doing the same run of 75miles, considering 55mph vs 75mph. I would finish in exactly 1 hour. Whereas you are saving gas but going slower your car would be running longer, 20 mins more, wouldn't that balance off fuel consumption? Let's say we are both on cruise controls and no a/c, drafting or whatever affecting the car.

[rningonfumes]

Apples to oranges? The only thing wasted here is time which I would need to account for ie leave sooner.

You traveled 75 miles at 75 mph
I traveled 75 miles at 55 mph.

This was more complicated than it needed to be but I'll play.

75 miles / 40 mpg = 1.75 gallons used.
75 miles / 50 mpg = 1.50 gallons used.

I'm being conservative on both sets of numbers.

Let's try it differently.

10 gallons x 40 mpg = 400 miles
10 gallons x 50 mpg = 500 miles.

I like these numbers, easier math lol. I went an extra 100 miles over you at the expense of time. Doesn't matter really for daily commutes but the time might build up if it's say a road trip.

[UltimateMonky]

Originally Posted by Ilovemyyaris

I go about 55 plus or minus all the time. I generally get at least 40 or more mpg. Normally about 45 - 50 mpg if it's just highway.

People hate me for it though. Sometimes people honk, middle fingers, angry red necks shouting out the window, and etc. Not sure what's so hard about using the other lane for to pass. I've even seen some other people driving the Yaris wizz past me. Am I the only person who lives in GA who knows about this?

Sometimes I follow big rigs if I need to get somewhere faster. I don't do that much because I heard it's dangerous. Just wondering. Anyone know why exactly they say it's dangerous? As long as you're not right up on them. Doesn't it take them a lot longer to come to a stop than a small car?

I too live in Georgia and the thing I hate most here, and really most places I've driven, is passage ettiquite! When I have to take the 3 or so hour trek up to Atlanta on 16 it's like hell. People either just cruise at 65 in the left PASSING LANE without a care in the world or ride your ass when you're doing 76 or so in the right lane. As far as I'm concerned the left lane is just a passing lane and you shouldn't take your whole trip on it, it ruins the flow of traffic. Just my little rant!