Speed vs. Fuel Economy - 2004 Chevrolet Aveo sedan (1.6 L, 4-sp automatic)
 

As an experiment for one of my college courses, I decided to test how speed affects fuel economy. This was a fun experiment as I was able to confirm other graphs made with different cars

Here is my data:
Temp: 69F
Pressure: 30.29"
Avg Wind Speed: 2.53 mph
Road Length: 0.85 miles, slightly inclined

Speed(mph) South(mpgUS) North(mpgUS) Average(mpgUS)
__________________________________________________ _______
25-------------38.5-------------40.5-------------39.5
30-------------40.3-------------43.3-------------41.7
35-------------41.2-------------45.6-------------43.3
40-------------40.1-------------47.0-------------43.3
45-------------38.7-------------45.1-------------41.7
50-------------41.5-------------46.7-------------43.9
55-------------38.9-------------42.0-------------40.4
60-------------36.2-------------38.5-------------37.3
65-------------33.7-------------37.2-------------35.4
70-------------32.8-------------35.1-------------33.9

There you have it. A few things to note: My fuel economy stays relatively the same between 30 and 55 mph. I have a 4-speed automatic transmission, and my car was in third at 45 mph (I don't like how my car doesn't shift earlier). At 50 mph is where I was at the lowest rpm range in the highest gear, hence the jump in fuel economy from 45-50 mph. Looking back on it, I wish I would have done 20 mph and 75 mph runs (possibly higher speeds too) to see a decrease in fuel economy at both ends.
One final note: I acheived 46.4 mpg on the 13.4-mile (starting from a stop and ending with a stop) drive back from the test road. I used pulse and glide between 60 and 45 mph.:thumbup:

My art student self tried to use Excel for the first time in about 8 years. Here are the results. Better than nothing? It would be great to get a few more runs for more consistent numbers but you can still see a general pattern.

http://i42.tinypic.com/2r4oeqc.jpg

Edit: can someone who knows what they're doing make a better graph please? I swear this would be 10x better if I did it by hand on graph paper. :(

Start by getting your data into two adjacent columns, with MPH in the left column and average MPG in the right column. Then select the data and insert an X-Y or scatter (two names for the same thing) chart.

Yeah, give me a few minutes and I'll throw one together.

Edit: Let's see if this works:

http://img.photobucket.com/albums/v4.../SpeedtoFE.jpg

I wonder what's the cause for the squiggle in the MPG graph in post #5.
In reality its not all that big, ~2 MPG, ~5%.

It could just be the result of it being only a single data run.

But I can accept that it happening just as the graph turns downward
may be more than just coincidence.

A +1 MPG adjustment at 45 MPH and a -1 MPG adjustment at 50 MPH would
show what I would consider to be a much more likely MPG graph.

Would access to a BSFE chart shed light on whats going on?

An inquisitive but semi-informed mind would like to enquire. :o

Yeah, you're probably right. Just minor noise. It has probably been compounded by the graph's close zoom, but I wanted the text to be big.

Additionally, I think it may have something to do with what Aveomiler observed about the OD not kicking in until 45mph.

He's in third gear up through 45 MPH. I'd like to know if the torque converter was locked up in third gear.

My wife's PT Cruiser had a four speed automatic. The torque converter would lock up in third gear if it was manually shifted to third gear.

Yeah my car stays in 3rd gear too long. At 45 it was in 3rd so my gas mileage dipped a little. I did another run at 50 mph with my car in 3rd gear instead of 4th to see the drop in mpgs. I got under 40 mpg for that run. I would really like it if my car would let me shift a little after 40 mph because I think I would be able to get great gas mileage at that speed.

Thanks Kodak for that graph. Aveo, does your car have manual mode? That could be very useful.

Also, I'm kind of disappointed at the EPA for GM's "economy" car- combined is only 2MPG better than the Probe. You'd think it would be more eco-minded! :(