Maximizing MPG on Long Uphill Grades

withersea · 08-02-2006, 10:00 AM

I have had the car now for approximately one month. My 33 mile drive to work has a couple of long uphill grades on the interstate. I'm currently averaging (computer) 47-48 MPG on the drive to work but coming home (more downhill) 49-50 MPG. Any tips for maximizing MPG's on those long high speed uphills?

**efusco** · 08-02-2006, 10:14 AM

Not much.
1)If there's a downhill slope prior to the uphill grade and traffic isn't an issue you can try to glide/accelerate on the downhill and utilize that momentum to get you part way up the uphill section. I do this quite a lot on the hills in my area and am convinced it makes a big difference over time.

2) Turn OFF the cruise control before you start the uphill or start accelerating slowly before the cruise kicks in. As you're aware there's a delay of 1-2mph before CC kicks in and when it does it accelerates quite aggressively to try to get back up to speed. If you can maintain the base speed at a lower fuel burn rate that will help a little.

3) Lower your speed as much as reasonable and even allow the car to lose speed as you climb...again, traffic conditions permitting.

My scenario....I glide/hyperstealth down a hill as I approach an uphill section. Maintaining a very gentle acceleration on the flat before the uphill to maintain speed I slowly let the speed bleed off as I go up the rise. Sometimes I can get over the smaller hills without applying significant ICE power, sometimes on a tall steep hill it just gets me 10% of the way up...but at least I wasn't having to apply full ICE power from the base of the hill to maintain speed. Then, traffic permitting, I let ~5mph bleed off as I approach the summit and then regain the speed slowly as I crest the hill and begin the next downhill section...

This is going to have a subtle effect, but I think, if you track such, you'll notice an improvement in mpg of 2-4mpg over the next few tanks if you can do this approach.

randreed · 08-02-2006, 10:23 AM

Timely advise - THANKS!

I'm just about to head back to NJ from Boston and there are a LOT of hills on I-84. I used CC all the way here with windows open, and did not change my established 48.5 average. I'm going to follow your advice on the way back with windows up and AC on low to see if that combination makes a difference.

**efusco** · 08-02-2006, 10:31 AM

I didn't really mention my speeds here, perhaps I should.
I allow my momentum to pick up as much as possible. On 55mph roads that sometimes means speeds of 80+mph by the time I hit the bottom of the hill (and that's using NO GAS power)! If you do not feel safe with that or there are other people on the road or many places where cars could enter PLEASE use your head and take safety into consideration first. I'd say that most of the time my speeds peak at 65-70mph on those 55mph roads and I let it blead off to around 45-50mph, but these are on rural roads in SW Missouri. On the highway/interstate I do allow momentum to pick up, but never let my speed drop below the limit (70mph on the freeway and 60mph on the hwys I usually drive).

And yes, I think conservative use of the AC (78-80 degrees F on auto AC setting) with windows up is a bettery, more fuel efficient and more comfortable way to drive, esp. on the highway.

mastergunnera8 · 08-02-2006, 10:38 AM

I turn my AC off just before the incline begins, then switch back on at cresting...

**efusco** · 08-02-2006, 10:42 AM

<div class='quotetop'>QUOTE(mastergunnera8 @ Aug 2 2006, 09:38 AM) [snapback]296253[/snapback]</div>

Quote:

I turn my AC off just before the incline begins, then switch back on at cresting... [/b]

You can do that, but there's really not much point and the savings are negligible if any. The Prius auto-AC system will actually decrease the output of the AC during times of high demand, like acceleration. It doesn't turn it off completely to avoid the cabin warming up which would necessitate a higher AC output to cool it off again...as would occur if you turn it off completely.

I used to do that too, but am convinced the benefit isn't there FE wise. That said, I DO think you can get a power boost by turning it off if you need it for a long steep climb.

ken1784 · 08-02-2006, 10:54 AM

<div class='quotetop'>QUOTE(withersea @ Aug 2 2006, 11:00 PM) [snapback]296233[/snapback]</div>

Quote:

Any tips for maximizing MPG's on those long high speed uphills?
[/b]

My bet is do not use the battery power, which means no yellow arrow from the battery on uphills.

Ken@Japan

randreed · 08-02-2006, 10:56 AM

<div class='quotetop'>QUOTE(ken1784 @ Aug 2 2006, 10:54 AM) [snapback]296263[/snapback]</div>

Quote:

My bet is do not use the battery power, which means no yellow arrow from the battery on uphills.

Ken@Japan
[/b]

That's an interesting idea - how can you force that to happen?

**efusco** · 08-02-2006, 11:02 AM

<div class='quotetop'>QUOTE(Rand Reed @ Aug 2 2006, 09:56 AM) [snapback]296264[/snapback]</div>

Quote:

That's an interesting idea - how can you force that to happen? [/b]

Search Dead banding or dead-banding on PC and you'll find tons of info. Basicly you just feather the gas pedal until all but the yellow arrows (ICE to wheels) disappear on the Energy display.

While this is definately the single most fuel efficient way to go, it's completely impractial in real-world driving. All but the gentlest slopes will cause dramatic loss of speed due to the very low power output of the ICE in this situation. One could try it, but I think you'll have more frustration than you want for a tiny gain in mpg.

jtullos · 08-02-2006, 11:19 AM

In my experience (approx. 3000-4000 ft. climbs at 55 MPH and 70 MPH), there are two types of climbs to consider. If it's done intelligently, and there are points where the climb levels off or even drops for a short distance (needed for trucks), then take advantage of that. Otherwise, accelerate a little more on the gentler slopes, but try to hold your speed on the long, steep slopes. If you've got a short but steep slope, go ahead and lose a little speed. But when you've got the worst ones to deal with, you just have to suck it up and remember that you will get wonderful mileage going back down the hill.

08-02-2006, 10:14 AM	#2
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 14,210 My Car: 2004 Prius Package: #9 Nominated 1 Time in 1 Post TOTM Awards: 0 Friends: 24	Not much. 1)If there's a downhill slope prior to the uphill grade and traffic isn't an issue you can try to glide/accelerate on the downhill and utilize that momentum to get you part way up the uphill section. I do this quite a lot on the hills in my area and am convinced it makes a big difference over time. 2) Turn OFF the cruise control before you start the uphill or start accelerating slowly before the cruise kicks in. As you're aware there's a delay of 1-2mph before CC kicks in and when it does it accelerates quite aggressively to try to get back up to speed. If you can maintain the base speed at a lower fuel burn rate that will help a little. 3) Lower your speed as much as reasonable and even allow the car to lose speed as you climb...again, traffic conditions permitting. My scenario....I glide/hyperstealth down a hill as I approach an uphill section. Maintaining a very gentle acceleration on the flat before the uphill to maintain speed I slowly let the speed bleed off as I go up the rise. Sometimes I can get over the smaller hills without applying significant ICE power, sometimes on a tall steep hill it just gets me 10% of the way up...but at least I wasn't having to apply full ICE power from the base of the hill to maintain speed. Then, traffic permitting, I let ~5mph bleed off as I approach the summit and then regain the speed slowly as I crest the hill and begin the next downhill section... This is going to have a subtle effect, but I think, if you track such, you'll notice an improvement in mpg of 2-4mpg over the next few tanks if you can do this approach. __________________ Evan E. Fusco, MD Seaside 04BC9/OEM EVb/NAV & auto-BT/XM Radio, CAN-View, Shark Fin, BT Stiff. Plate, Skid Plate & Strut Support

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08-02-2006, 10:00 AM	#1
withersea DNF is better than DNS Join Date: Jun 2006 Location: TN Posts: 1,145 My Car: 2006 Prius Package: #7 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 2	I have had the car now for approximately one month. My 33 mile drive to work has a couple of long uphill grades on the interstate. I'm currently averaging (computer) 47-48 MPG on the drive to work but coming home (more downhill) 49-50 MPG. Any tips for maximizing MPG's on those long high speed uphills?

08-02-2006, 10:23 AM	#3
randreed Same as it ever was . . . Join Date: Jul 2006 Location: West Milford, NJ Posts: 591 My Car: 2006 Prius Package: #5 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 3	Timely advise - THANKS! I'm just about to head back to NJ from Boston and there are a LOT of hills on I-84. I used CC all the way here with windows open, and did not change my established 48.5 average. I'm going to follow your advice on the way back with windows up and AC on low to see if that combination makes a difference.

08-02-2006, 10:31 AM	#4
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 14,210 My Car: 2004 Prius Package: #9 Nominated 1 Time in 1 Post TOTM Awards: 0 Friends: 24	I didn't really mention my speeds here, perhaps I should. I allow my momentum to pick up as much as possible. On 55mph roads that sometimes means speeds of 80+mph by the time I hit the bottom of the hill (and that's using NO GAS power)! If you do not feel safe with that or there are other people on the road or many places where cars could enter PLEASE use your head and take safety into consideration first. I'd say that most of the time my speeds peak at 65-70mph on those 55mph roads and I let it blead off to around 45-50mph, but these are on rural roads in SW Missouri. On the highway/interstate I do allow momentum to pick up, but never let my speed drop below the limit (70mph on the freeway and 60mph on the hwys I usually drive). And yes, I think conservative use of the AC (78-80 degrees F on auto AC setting) with windows up is a bettery, more fuel efficient and more comfortable way to drive, esp. on the highway.

08-02-2006, 10:38 AM	#5
mastergunnera8 Join Date: Jun 2006 Posts: 46 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I turn my AC off just before the incline begins, then switch back on at cresting...

08-02-2006, 11:19 AM	#10
jtullos Join Date: Jan 2006 Location: Dayton, NV Posts: 172 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	In my experience (approx. 3000-4000 ft. climbs at 55 MPH and 70 MPH), there are two types of climbs to consider. If it's done intelligently, and there are points where the climb levels off or even drops for a short distance (needed for trucks), then take advantage of that. Otherwise, accelerate a little more on the gentler slopes, but try to hold your speed on the long, steep slopes. If you've got a short but steep slope, go ahead and lose a little speed. But when you've got the worst ones to deal with, you just have to suck it up and remember that you will get wonderful mileage going back down the hill.