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-   -   Speed vs. MPG charts (post 'em if you got 'em) (

bluejoey 11-16-2010 06:33 PM

Speed vs. MPG charts (post 'em if you got 'em)
Ever since I started lurking on Ecomodder (a few years ago), I've always been keen on the speed vs. mpg charts. Not only do they clearly show the influence of speed on mileage, they also provide a handy reference for people who don't yet have instrumentation, or folks interested in the efficiency slopes of other vehicles. I've searched and haven't found any collections of charts here, so I'm hoping this might become a place to store these charts as a reference. To kick things off, here are a few I've found from users here:

NOTE from admin: if you add a graph, PLEASE also include a link to the source site/page. Thanks!

2006 Toyota Corolla 1.6L Auto by MetroMPG

1998 Pontiac Firefly / Geo Metro 1.0L Manual by MetroMPG
from Speed kills: testing MPH vs. MPG in top gear -

2002 Nissan SE-R, 2006 Scion, Elantra by SentraSE-R

Assorted cars by Auto Bild Magazine
from Speed kills: testing MPH vs. MPG in top gear -

If you have any more, please post them. If you have an instrument (SGII, Ultragauge, etc) and are willing to compare your speed to mpg at a variety of speeds, that would also be appreciated. I would be happy to make charts for anyone who supplies me with a range of figures.

RobertSmalls 11-16-2010 06:44 PM

Thank you for creating this thread. We should all include the source of our data, so folks know how good the data is.

This was posted on PriusChat and linked to by

Also, when Wayne Gerdes reviews a car, he does an mpg vs mph test on it.

Edit: Here's his data on the Honda CR-Z, 6mt, with cruise control and Eco Mode engaged. Ambient 66-68F.


Originally Posted by Wayne Gerdes
* 45 mph - 58 mpg
* 50 mph - 53 mpg
* 55 mph - 49 mpg
* 60 mph - 46 mpg
* 65 mph - 43 mpg
* 70 mph - 38 mpg

Frank Lee 11-16-2010 07:53 PM

Periodically we get claims of higher fe at higher speeds, or at a certain speed range that isn't near the low end. I suppose it's possible if an engine has a peaky BSFC combined with certain gearing and loading... but most of the time I'm tempted to chalk those claims up to faulty fe calculating.

bluejoey 11-16-2010 11:32 PM

Hey RobertSmalls, thanks for the Prius and CR-Z additions!

Agreed Frank Lee. This claim seems to be more common around folks who own fast cars, but I think it's more psychological than factual. I haven't seen much data that contradicts the "lowest RPM in highest gear" rule of thumb for peak mpg.

Found another one!

2005 Corvette 7.0L Manual by MetroMPG

Frank Lee 11-17-2010 12:12 AM

About 1233 rpm @ 55 mph- jealous!

My impression is that the pickup truck driving crowd in general are most prone to making a higher speed/higher fe claim, even though aero kicks their butts the worst.

slowmover 11-17-2010 11:37 PM


Originally Posted by Frank Lee (Post 204537)
About 1233 rpm @ 55 mph- jealous!

My impression is that the pickup truck driving crowd in general are most prone to making a higher speed/higher fe claim, even though aero kicks their butts the worst.

It's the crowd involved. It is not one that has high regard for FE, in general. I always get a kick out of someone towing a big 5'er claiming that slightly 70+ is the best, all-around, in mpg. It tells me -- these claims -- that no records about total fuel use are in place.

Same for "tuners" that magically increase both HP and FE. While such gains are theoretically possible they are essentially limited to stop-and-go traffic (as admitted by the president of one such company). I have yet to see good records combined with steady state driving to substantiate any claims viability (on otherwise stock trucks).

As to the topic I only know that empty or loaded (7k to 9k) my truck will, at 58 mph/1,725-rpm repeatedly, endlessly, deliver a 24-mpg average no matter winds, rain, day, night, traffic, etc. Can go up to 27 mpg, and, if the overhead display is interpreted, nearly 30-mpg at 50 mph over a 40 mile Louisiana backroad. Would be great to run a long course at 45 mph to see the "true" high (and experiment to run down the perfect rpm.) 24-26 is reported by other men in the South and South Central US with similar trucks, so my experience is not uncommon.


Frank Lee 11-17-2010 11:39 PM

Used to have a 460 F250 and it was impervious to conditions too- same fe no matter what.

NHRABill 11-18-2010 03:08 AM

I have seen no change since weather has started to change for my Tahoe consistent on last few tanks only thing has changed is Gas prices rising ...

I am just shifting in 4th @45mph sweet spot seems to be 60mph running @ 1700rpm.

Nice thread interesting #'s

Frank Lee 11-18-2010 05:16 AM

It would be interesting to see if your fe is better at 50 or 55 or 65 rather than 60.

When towing my F150 has a very small sweet spot (as far as keeping the E4OD in OD is concerned) at between 52-55 mph; under 52 and it won't give OD because of the slow speed and load, over 55 and it won't give OD because of the increased aero and rolling resistances. Mind you this is on really flat highway- the slightest rise or gust kicks OD out too. I know when towing OD "should" be locked out but I really like OD, what can I say? Perhaps I am ODing on OD.

rbrowning 11-18-2010 11:54 AM

I wonder what caused the hump in the curve for the Corolla? Aero? Surely it would have been in top gear before 60. :confused:

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