WTF? Better MPG's in the Hills than flat?? - Ford Powerstroke Diesel Forum
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post #1 of 8 Old 10-14-2013, 04:51 PM Thread Starter
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WTF? Better MPG's in the Hills than flat??

I don't post too much, but thought I'd ask. . . why would I get better mileage driving through the mountains at 70mph than I would on flat ground at 65?? Hand calculated. . .16.4 in the mountains, 12.6 on the flats. Last week I took a road trip from northern CA to Yuma AZ, back to San Diego, then to Vegas, then back to northern CA.

Truck is an '03 with a 7.3. . .here's what's been done to the truck-
8"lift, 35" x 12.5 tires
3.73 gears
Injectors- done before I purchased truck, I'm told a little bigger than stock
Tranny/TC/Valve body- new
Cold Air Intake- new
Turbo back exhaust- new
Turbo- Garret GTP38R- new
Up Pipes, Y Pipe, pedestal- new
Fuel Filter- replaced 4k miles ago
Edge set at 100

I would think mileage would be much better on flat ground, with a lower rpm, not working at all. On the last leg of the trip, I fueled up before the mountains and directly after, just to check mileage to see if I was an idiot. Anyone??

Thanks.
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post #2 of 8 Old 10-14-2013, 05:04 PM
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Higher elevation requiring less fuel? If you took I80 back into CA, I really have no idea, unless the partial throttle going back down increased the average that much.

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post #3 of 8 Old 10-14-2013, 05:10 PM Thread Starter
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Originally Posted by Macon View Post
Higher elevation requiring less fuel? If you took I80 back into CA, I really have no idea, unless the partial throttle going back down increased the average that much.
That's what I thought on the first leg of the trip. On the way back, it's a much more gradual climb, for a much longer distance than the descent. That's where I got the best mileage. I dunno. . .
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post #4 of 8 Old 10-15-2013, 08:44 AM
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It's probably a result of different filling levels when you filled up.
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post #5 of 8 Old 10-15-2013, 09:19 AM
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Quote:
Originally Posted by Matthews View Post
It's probably a result of different filling levels when you filled up.
That's what I would suspect also. Doesn't seem logical that flat ground, going slower will give less mpg... then increasing speed and engine load results in higher mpgs.

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post #6 of 8 Old 10-15-2013, 08:03 PM Thread Starter
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Originally Posted by RollinEarly99 View Post
That's what I would suspect also. Doesn't seem logical that flat ground, going slower will give less mpg... then increasing speed and engine load results in higher mpgs.
I'd agree, it makes zero sense to me; this is why I paid such close attention on the way back. . . filled till it spilled out(topped off) the last 3 tanks. Would there be anything that'd make the truck run more efficient when it's working harder? Or, more importantly, is it possible that somethings not working correctly(fuel pump/hpop/???) when the truck is under lower RPM's/less boost?

This thing's been a turd since I purchased it. Turbo, pedestal, up-pipes, Y pipe, and tb exhaust made a HUGE difference. Still seems like it's lacking. . .and I'd think mileage would be better. Dunno.

Thanks. . suggestions appreciated.
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post #7 of 8 Old 10-15-2013, 08:19 PM
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SOMETHING WITH THE EDGE MAYBE?
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post #8 of 8 Old 10-15-2013, 08:29 PM
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If your rpms are too low at 65mpg that lugs the motor and makes it less efficient.

Most people report that the 7.3 is most efficient if cruised at 2000-2200 rpm. So if that's the case, 70 mpg might be better for you.

Also, I've noticed a difference in mpg before from one brand diesel to another.

Too many variables to say for sure.

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I love finally having my truck back... that 7.3 dog that I was driving was just not cutting it.
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