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post #1 of 33 (permalink) Old 06-02-2008, 02:49 PM Thread Starter
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2k RPM Experiment

So with ga$ prices creeping up over $4/gal, I decided to try a little experiment in my Commander. I was averaging 12.9 mpg with 65% highway driving. I drive around 80 mph on the highway and around 10 mph over on the secondary roads.

My experiment was to see how much I could increase my mpg by keeping the RPMs at or under 2000 RPM. Before I post my increase, I will describe what it was like:

- It was difficult to accelerate with such slowness but I did "kinda" got used to it. Traffic would sometimes accelerate faster than me, but not by much.
- On the highway, 2000 RPM = ~68 mph (GPS calculated). This was the more difficult thing to do since I was driving around 12 mph slower than I normally do on the highway.

After running two full tanks like this, I was averaging 15.9 mpg... a 23% increase.

Final Thoughts: Although difficult to change my driving habits, saving $17 on each fill up is worth it for now.

I want to know if anyone else has done something like this or has any other techniques that might help.

John

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post #2 of 33 (permalink) Old 06-02-2008, 03:02 PM
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That's a substantial increase but I don't think I could retrain myself to do it. I guess it's worth a try though.

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post #3 of 33 (permalink) Old 06-02-2008, 03:12 PM
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Since your hiway mix is so high I'll wager that you would retain 15mpg+ if you drove in town as normal but kept to the 68mph highway speed. May go up if you go ahead and drop to 65 on the highway. Speed kills our highway mpg, that's for sure.
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post #4 of 33 (permalink) Old 06-02-2008, 03:31 PM
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Smoky the Bear says:

Quote:
Originally Posted by RedCommander
Speed kills


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post #5 of 33 (permalink) Old 06-02-2008, 05:10 PM
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I've noticed that keeping the RPMS BELOW 2k gives a significant increase in MPG. I shoot for 1700-1800.

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post #6 of 33 (permalink) Old 06-02-2008, 05:18 PM
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Also don't forget that cruise control is your friend, if it's safe to use. (I have a hard time with it in heavy traffic.) I've noticed an easy 1+ MPG increase on large vehicles like a Suburban by using cruise as opposed to using the gas pedal.
That computer is much more precise than my right foot.
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post #7 of 33 (permalink) Old 06-02-2008, 06:38 PM
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I have recently set the cruise on 66MPH (It is actually more like 72 with the oversized tires) And I can get about 16-17 on the highway. If I crank it up to 70 (76) It kills the MPG down to about 14.
I also noted the EVIC is optimistic in its calculations even though with the larger tires it souldn't be..

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post #8 of 33 (permalink) Old 06-02-2008, 06:48 PM
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evic doesn't know about your larger tires, so those are not a factor in it's calculations. Now if you took it to the dealer and had them correct the tire size in starscan maybe it would be correct.
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post #9 of 33 (permalink) Old 06-02-2008, 07:04 PM
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I have a 2006, 4.7, QDII, Class IV Tow. I don't know your axel ratios. I purchased new and just went over 16,000. I live in Ft. Wayne and drive to Indianapolis. 2000 rpm = 73 mph. Going south against the wind I average 18.5. Coming home (North) with the wind I get 20.5. I always use Marathon mid grade. I went to northern Michigan two weeks ago, mushroom hunting. Again at 73 mph I got 20.5 and where 131 goes down to 60 north of Cadillac, it went up to 22.5 at 63 mph. I do not know if using mid grade helps, but around town, stop and go I always get 13.5 - 14.
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post #10 of 33 (permalink) Old 06-02-2008, 08:16 PM
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I know the EVIC doesnt know about my tire size so it should be giving me a much lower MPG than I'm actually getting. Bigger tires mean the engine has to work harder to turn the larger tires (higher gear ratio). Since the EVIC still thinks they're the same size, so the same number of revolutions per mile it should think it using more gas per mile. I think it is saying lower MPG than it did with stock tires but it still is higher than when I calculate it.
Oh, and tire size options in star scan don't go any larger than stock.... no where close to my size...

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