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

[PaleMelanesian]

So THAT is what a tall 6th gear will do. Wow! ~10 mpg better than my Fit all the way across.

What rpm do you run at 60 mph? I'm at 2800.

[fcporto]

Due to recent activity in this thread, I am re-posting my previous graph with some changes, namely:

1- new graph type, that takes into account the amount of Km made in each test run (and a rather colorful one...)
2- new data from recent runs
3- values are corrected for the computer average error (6.1%)

Mercedes C200 CDI (diesel), estate, manual gearbox

[PaleMelanesian]

100 mph? Really?

[fcporto]

Yes...
Very hard to keep a stabilized speed for so long at these speeds, so this is really an average. In German Autobahn, of course

[101Volts]

I found a site that gives detailed fuel economy information for vehicles at specific speeds. Here's one for the 3.0 Litre Dodge Caravan I sometimes drive:

2000 Dodge Caravan 3.0L V-6 fuel economy analysis (model for North America U.S.)

And here's one for the 84 Caprice Classic Sedan I drive (With not as much info):

1984 Chevrolet Caprice Classic Sedan 5.0L V-8 automatic overdrive fuel economy analysis (since September 1983 for North America U.S.)

I wasn't sure if I could post the graphs here legally, So I didn't.

Also, If searching for vehicles on that website and you want to get to a page like that you need to click on "see detailed fuel economy analysis" Under the vehicle's description, Not one of the big buttons.

And whether or not this site is quite accurate, I don't know. It might be a bit optimistic.

[Blue Angel]

Originally Posted by PaleMelanesian

So THAT is what a tall 6th gear will do. Wow! ~10 mpg better than my Fit all the way across.

What rpm do you run at 60 mph? I'm at 2800.

Not bad for a large-ish compact sedan that weighs 3000 lbs. If I remember right, it's reving almost right at 1500 @ 50 MPH, so at 60 it would rev about 1800 or so. It's a .61 6th gear with a 3.83 final drive and a 26.3" tall tire (215/55-17). No doubt a 6th gear in the Fit would pay off big time.

5th in the Eco is the same .74 ratio as the regular Cruze's 6th gear. That super tall .61 6th is probably responsible for 75% of the mileage increase over the standard car. With my Saturn I was always wishing for a taller gear, but not with this car.

There are a couple of 6 spd manual transmission options from some GM European diesel cars that have even taller gearing. I'm sure putting even taller gears in would suck a lot of the fun factor out of the car, but I drive for economy. Getting a transmission from Europe could be expensive, though!

[2003protege]

Originally Posted by PaleMelanesian

It would definitely benefit from lower rpm cruising. Not necessarily bigger tires, because there are weight and aerodynamic and rotational inertia penalties involved there. Just look at the RPM vs MPG chart and imagine what a 6th gear would look like. I want one.

Thanks so much for the numbers. I'm surprised to see that ratio on the Fit; I thought it would be better. This is one of my biggest complaints about my protege, like the fit it turns about 50 rpm per MPH putting anything close to highway speeds in the boy-racer range.

[Pawtuckett]

Originally Posted by 101Volts

I found a site that gives detailed fuel economy information for vehicles at specific speeds.

Thank you, 101. I've known about that site, but didn't know they had the simulated fuel consumption charts there.

From their site: "Estimated mileage (fuel economy) by constant speeds on top gear, steady ride without acceleration or braking, flat concrete or tarmac surface, no wind"


My real world results are definitely lower than these simulated results...I think. I'll have to pay attention on the way home today. The tank I'm working on now might get me over 800 miles. I sure hope it does!

[cmendes0101]

I want to make a chart for my cars but am a little unsure how this would work. How do you get a chart with increasing speed and mpg?

I'm assuming if I had instant mpg on a graph with speed it would jump around. Would I do something like drive 20mpg for a minute then get the avg mpg for that minute then increase to 30mpg etc etc?

[2000mc]

assuming you have a scangauge...
use trip mpg, reset the trip just as you enter your test section at the given speed. note your current trip mpg at the end of your test section. repeat the same section in the opposite direction and average the 2.

after all the runs at different speeds, i like to start over again to check data. my car seems to slightly increase mpg even after the thermostat has opened and will plateau after about 30mins of driving


and then theres also http://ecomodder.com/forum/showthrea...ery-11445.html