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steeve · 01-09-2019, 02:15 AM

Here are the details; I have been in a long term argument with a "expert" friend about this. My experience has always been that I get better mileage in hills or low elevation mountains. I recently decided to prove it to my friend by performing an accurate test. I drove my 3/4 ton 2008 dodge diesel, 6 speed automatic,down the canyon road from my home and marked both a beginning point and end point at the bottom of a 10 mile long mostly down hill section. I made a return run back up the hill on my way back home. I re-set my OEM fuel mileage instrument at the beginning points for both up hill and down hill of the same test section. So, going down, mostly coasting in high gear, with motor on, I averaged 59 mpg according to the instrument readout; then on the return trip, going up the same section, I got 17 mpg. Averaging the two, comes out to about 38 mpg for the total 20 miles of equal distance, up and down hill driving.
My theory is simply that I use practically no fuel going down hill, and just a bit more than flat-land driving going back up the hill. This is partly because of my driving style of using a "race-car line" (using the whole road), so that I do not slow down for corners much, or at all; I can carry my speed through the corners and not have to use fuel to accelerate back up to speed after exiting the corner. This amounts to maintaining a more constant speed, in spite of all the sharp corners. It is my usual driving habit and obviously saves more fuel than the typical driving style of the general public. Then, when driving up hill, I use just enough throttle to keep from blocking following traffic; I don't bury the fuel pedal, to maintain speed on the steep sections but do try to maintain enough speed to keep following cars from stacking up behind me, again, by driving the "fast-line" around the sharper corners, which tend to slow down most following drivers.
So, it looks to me that I have achieved about 65% better economy in the hills than my average flat-level highway driving of 23 mpg. My friend calls Bull-s**t saying that something is wrong....it can't be true, after all, he has millions of miles experience in the seat of an 18 wheeler. What do you think?

01-09-2019, 02:15 AM	#11 (permalink)
steeve EcoModding Lurker Join Date: Mar 2010 Location: costa mesa, ca. Posts: 7 Thanks: 0 Thanked 4 Times in 2 Posts	Ahhh, finally got my post to work Here are the details; I have been in a long term argument with a "expert" friend about this. My experience has always been that I get better mileage in hills or low elevation mountains. I recently decided to prove it to my friend by performing an accurate test. I drove my 3/4 ton 2008 dodge diesel, 6 speed automatic,down the canyon road from my home and marked both a beginning point and end point at the bottom of a 10 mile long mostly down hill section. I made a return run back up the hill on my way back home. I re-set my OEM fuel mileage instrument at the beginning points for both up hill and down hill of the same test section. So, going down, mostly coasting in high gear, with motor on, I averaged 59 mpg according to the instrument readout; then on the return trip, going up the same section, I got 17 mpg. Averaging the two, comes out to about 38 mpg for the total 20 miles of equal distance, up and down hill driving. My theory is simply that I use practically no fuel going down hill, and just a bit more than flat-land driving going back up the hill. This is partly because of my driving style of using a "race-car line" (using the whole road), so that I do not slow down for corners much, or at all; I can carry my speed through the corners and not have to use fuel to accelerate back up to speed after exiting the corner. This amounts to maintaining a more constant speed, in spite of all the sharp corners. It is my usual driving habit and obviously saves more fuel than the typical driving style of the general public. Then, when driving up hill, I use just enough throttle to keep from blocking following traffic; I don't bury the fuel pedal, to maintain speed on the steep sections but do try to maintain enough speed to keep following cars from stacking up behind me, again, by driving the "fast-line" around the sharper corners, which tend to slow down most following drivers. So, it looks to me that I have achieved about 65% better economy in the hills than my average flat-level highway driving of 23 mpg. My friend calls Bull-s**t saying that something is wrong....it can't be true, after all, he has millions of miles experience in the seat of an 18 wheeler. What do you think?