MPG vs Speed

Hi Guys,

I am fairly new to the forum so I was hesitant to share this at first, however I hope others can benefit from my “experimentation”. I know I have benefited from this forum many times, so I’d like to give back.

I made a chart of speed vs. MPG for my truck (4x4, Access Cab, V6, Automatic, no TRD, no SR5). Approximately 10 runs at each speed were conducted. I also included the data point “0 MPH = 0 MPG” – seems fitting. The line on the plot is a 3rd order polynomial best fit with the intercept forced to 0, 0.

My goal was to compare the results against EPA estimates and gain an understanding of what the ideal speed for optimal MPG was. As the EPA would note: “Actual results will vary for many reasons, including driving conditions and how you drive and maintain your vehicle.” So without further delay here is my procedure, assumptions/test conditions, and results!

Procedure:
1. Accelerate to desired speed, set cruise control
2. Reset Scan Gauge MPG average
3. Record average MPG for the test duration (3~5 miles)
4. Repeat!

Assumptions/Test Conditions:
• Same weather (no rain, high wind, ect.)
• Same stretch of road (“by speed” – I didn’t do 30mph on the freeway, likewise, I didn’t do 70 in a residential zone) Obey the speed limits!
• Used cruise control to maintain speed
• No changes to vehicle (tire pressure, oil, cargo, etc)
• Same distance (3~5 miles)
• Calibrated Scan Gauge II
• Michelin X Radial LT2 tires (Sam’s club version of the LTX M/S2)
• Brush guard

If the response to this is good I am also considering posting the results of a years’ worth of fuel economy vs. all available weather conditions (temperature, humidity, precipitation, wind speed, wind direction, etc.) as provided by NOAA. I have not yet completed the year, however will be in June. I will be using MiniTab (statistical software) to analyze the response and statistical significance of the interactions between each of the variables and fuel economy. Who doesn’t want to know how temperature, humidity, etc. affect MPG. I swear that when it’s hot, the truck is more sluggish than normal – But I want to know for sure!

Regards,
Chuck

 

So if I understand your chart you got 28MPG at 35MPH under optimum conditions, correct?

 

I have found my truck loves around 58mph, gets me around 24mpgs ish according to my ultragauge which usually averages about 1mpg off. I always take back roads if I have the chance. I'm a bone stock TRD Offroad DCSB 4.0 with 265/75 mud terrains.

 

I would be interested in seeing your long term analysis. This is a pretty good breakdown of cruising speed MPG. I like that all of your data points with the exception of the 30mph run are within 3-4mpg. Pretty consistent readings and gives me a better understanding of how my speed is affecting my cruising MPG.

 

Yeah that's right.

 

It surprised me that 30 mph had the most variability. Have not given it much thought, but I'd be curious to hear others ideas.

 

Two fill ups after plugging in the new ultraguage and I got
21.5 mpg and 20.5 mpg

That's the best gas mileage I've ever calculated

My wife said I was driving like her grandmother but I was trying to keep the Instant MPG as high as possible

I kept the RPMs under 2000 as much as possible

I even reset the CEL on my fatherinlaw's ford taurus with and then plugged it back in

Very cool gizmo

 

Could be the fact at ~ 31 mph you can be in 5th lockup or not... Hence the variance. I will say these findings are about spot on to what I have found.

 

That is great to hear. Interesting thought on 5th gear, I think you may be correct.

 

This is interesting. Usually vehicles peak around 50-55mph. The bell curve effect is accurate for sure. Driving slow means the engine runs longer for distance travelled, driving too fast means you're using way more HP than what would be needed at 10mph less.

 

ppl

 

ya 29 and change mpg works, and no its not stock.

 

ppl.

 

ya I use the metric system in the US...

 

ppl.

 

sigh...

 

...let see...carry the one..