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Discussion Starter · #1 ·
Intuitively, it seems that in Mountain Mode, the additional steps in the energy chain would reduce performance, but:

Locomotives and ships use engines that drive generators that drive motors that drive the propulsion mechanism (propeller, wheels). In such complex "serial hybrid" systems, operating cost reductions must justify the expense of the additional components in the chain, overcoming inherent losses at each step.

The Volt inserts a battery in series with such a serial hybrid system, which enables the engine to run more efficiently than in a typical serial hybrid, because the battery buffers generator output and enables the engine to operate optimally, with little variation in load.

Yesterday, I took a rare trip - 200 miles - in my 2012 Volt, and did some experimenting. My impression is that by using Mountain Mode I got incremental miles from the system. I felt that intermittent use of MM actually extends range... is that possible?

Surely someone has MEASURED the efficiency of the system in Mountain Mode. Can you point me to such studies?

Thanks!

PS - at 33k miles, my '12 Volt is still the best car I've ever owned (the list began in 1954 and includes a lot of interesting and fine cars).
 

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It's a favorite discussion topic here - actually the topic that got me to register instead of lurking some more, well over three years ago. Search for gaming mountain mode or mountain mode games and you should turn up a couple dozen threads through the years.

The answer isn't simple. If you put a fair amount of thought into it and are careful about exactly when you're in mountain mode and when you're in EV mode burning off the miles, it is possibly to beat the car's programming - by about 10% in the best cases I've seen valid testing on.

However, it isn't a gimme. The car is pretty smart, and is doing something sorta similar to the mountain mode cycling on its own between 35 and 65 mph, but with lower engine speeds and a much smaller cycle range. Most of the time people get about the same results cycling mountain mode as just driving - and if you choose your timing poorly, it can actually cost you up to ~15% more fuel to cover the same ground (adding mountain mode charge requirements on top of freeway cruise and a hill of any kind drives the engine up well past the efficient range.)
 

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Discussion Starter · #3 ·
Excellent information - thanks.
I'll follow my own advice to prospective and new Volt owners: Just drive it.
 

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Yep. I think I've only hit Mountain Mode once in my Volt, and I've had it a bit over a year now. I do use Hold in certain situations.

Mostly if I know my trip will be more than battery range, which often times outside of my commute it is, I'll hit Hold. I'll try to use Hold when I'm on the highway and switch back to Normal when I hit surface streets.

Right now, I live off of a highway. I have to go down the highway (65MPH speed limit) for at least 8 miles (each direction) to get anywhere except the local grocery store and the local WalMart. The 'rents house is about 40 miles. What I'll end up doing is hit Hold right after I get on the highway and get up to speed, then switch back to Normal when I have to cross through the city to get to the other highway. Then back to Hold down that highway, and then Normal when I exit for the last few miles to the 'rents. Then on the way back, I "just drive it" because I know the battery won't make it, but I'll most likely be on the highway for the last bit.

Did this a couple times over the last couple weeks and usually hit about 38 miles on battery and about ~40MPG on the engine.

Good thing is I'll be moving a lot closer in, so I may modify behavior.
 

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Here is one of the most remarkable posts (http://gm-volt.com/forum/showthread.php?139985-Three-years-already&p=1940410#post1940410) that I've read regarding Mountain Mode on long trips:

2013 Volt here w/Hold mode and I find myself hardly using it anymore. I prefer mountain mode for long-distant trips and used this exclusively during the couple of cross-country trips this last summer...
Since my 2011 Volt does not have Hold Mode, I've always used MM for long trips. It works great for me.
 

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I have a 2012, and I use MountainMode not to gain MPG, but to avoid NVH and short runtimes. I have a 56 mile drive that has highway, city streets, plus a few stops, that I do routinely. If I let the Volt stay in normal mode, it happens to spend most of the time on this drive running the gas engine on the city streets, and using battery on the freeway. There's also at least one place where it's likely to switch to gas about 30 seconds before I park. I preferring using Electric in stop & go traffic, and gas on the highway, so I use Mountain Mode to game the system a bit.
 

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