I have a mind to make a spreadsheet that will illustrate economy to speed in relation to Odometer reading. This will hopefully render a good illustration of diminishing returns, ideal speeds, and the consumption effects of the engine getting some time on it. This is not an mpg meter; there are plenty of threads for that.
What I need from all willing participants is to head out to a nice and level road, make some measurements, and either send me a PM or reply in this thread with the following info:
Current Odometer reading:
MPG at 5 mph intervals, starting at 30, finishing at 65.
For example, here's my readings taken today. I actually made 3 passes, and averaged them out.
1303 miles
30 = 46.8
35 = 48.2
40 = 48.4
45 = 48.8
50 = 51.2
55 = 50.8
60 = 46.8
65 = 43.6
As you can see, my car seems to favor 50 mph (wish I'd get that avg per tank!), and that may not be the case across the board, so let's find out. The more I get, the more accurate and fluid this chart can become, so the more the merrier! Have fun!
Should specify A/C on/off, windows/cabrio open/closed, tire pressure checked?
Sounds interesting. Your spreadsheet might become more complex than you imagined if the above factors are considered though.
Just for fun, I may get some measurements this afternoon.
Good point. I should have mentioned something about that, and those variables, I won't integrate. My intentions are for this to be a cross-section of however the driver drives on a typical day.
On the two occasions I've had to run straight and true... I can attest that your readings at 50MPH through 65MPH are in line with my experience.
At 70 and 75MPH economy drops down to around 40 and 35MPG respectively. My experience is with A/C on, Passion, level roads. Tire pressure slightly above rated (32 front, 38 rear).
Measured when the engine had about 900 miles on it, a couple months ago. I was driving and people buzzed around me, so I wasn't about to write anything down. A relative, +/-5MPG range is good enough for me.
I've mentioned it before, road material is a big player. I have one road I travel on, no matter what I do at 60 mph I'm reading 42 mpg always (I have a lot of wheel time on this particular road). Also, this is on days with no wind. Sometimes I do occasionally catch a tail wind coming home and get 52 mpg on the same stretch for 60mph.
On another stretch of road I road I use for heading to work I'll do 49mpg at 60mph. This road looks identical to the other but apparently is cheaper material, at least that is what the state claims. The speed limit is lower due to it being slick on wet roads, FYI the police don't enforce the speed limit there for whatever reason so the traffic flow remains at the 60mph despite the 45mph speed limit.
Just keep in mind road material & wind will be factors in adding a little bit of variants.
That being said. 50-55 mph seems to be the sweet spot for my car - most mpgs there no matter what road.
I did a little data gathering this afternoon. I used a digital voice recorder to take notes and entered the data into my spreadsheet when I got home. Most of the values are the average of from 2 to 13 observations for that field. No question, this would be more accurate with the benefit of cruise control, but I did the best I could. Didn't care for a speeding ticket this afternoon so 80 MPH is the Max.
Odometer at start of test approximately 1400 miles.
Tire air pressure checked and corrected the day before.
Windows and Cabrio closed for tests.
Fuel is Chevron 93 Octane.
Speed, RPM and MPG from Scangauge II.
Two sets, first with A/C OFF, and then with A/C ON
W I T H
A I R C O N D I T I O N E R
Speed Gear .. RPM ... MPG
5 ........ 1 .... 1185 ... 8.8
10 ...... 1 .... 2375 .. 12.7
10 ...... 2 .... 1349 .. 19.1
15 ...... 1 .... 3531 .. 13.0
15 ...... 2 .... 2100 .. 22.6
35 ...... 4 .... 2340 .. 34.3
50 ...... 5 .... 2480 .. 37.3
55 ...... 5 .... 2750 .. 32.4
60 ...... 5 .... 2975 .. 28.4
65 ...... 5 .... 3238 .. 26.9
Notice that Feral_Collie's MPGs are substantially higher than mine. Also, his peak around 50 MPH, where mine peak at a much lower speed. Hmmmm.
My overall MPG at 1,322 miles with 39.336 gallons is 33.61 MPG. I do tend to drive sporty ... but, THIS was a controlled test. Something doesn't seem right here.
Careful, I am now a certified Jerk for not acknowledging there is a 3-4 mpg penalty for turning on the AC prepare to be demonized. LOL
nice effort karl
The only control measure required for this experiment of mine is a level road, so wherever, however one drives is trivial here.
There are so many external, internal, and operator factors that affect economy that I would need more than Microsoft Excel 98 and an 8 year old laptop computer to make an accurate rendering.
Thanks for the input so far. Keep 'em coming everyone. So far, it looks like it'll be 5000 mile intervals.
Imo, running these tests in low mileage Smarts, while fun, is just a drill.
The MPG changes dramatically up through about 5k on the ode. Ours settled in at about 3-4 k.
We now have 15k+ and run,"ball park", 37 W/air city. 40-45 mixed. (80+mph often).
We have never logged under under 34mpg, and of course best MPG occurs in cold weaher, with air off, where we touched 50 Mpg, after around 3k on the ode.
No Scangage here, just pencil and paper, but we have been expensing work cars for many years. A2Jack.
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