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You may call me naive or simplistic, but I just read the manual and use the grade of fuel the manufacturer recommends. Their engineers designed the engine and its management systems, and as in the Volt, they know the unique storage and lower rate of usage situation. They surely know that premium fuel is more costly and could be a detrement to sales, yet they specify it for that specific vehicle. There is a reason that they designated premium fuel.

For the last 20 years I owned cars that specify premium fuel (Volvo turbos, Gen1 Volt.) The forums I followed were full of the gas grade controversy. Lots of "Yeah, but..." - "What about this situation?" - "But my car runs fine . . ." stuff.

Will those cars run on lesser grade fuel? Sure - with the modern engine management systems they could probably detune sufficiently to run on some gaseous sludge from a rusty barrel in a third world jungle - but at what cost to the engine life and performance? And the seat-of-the-pants dyno is not an accurate gauge of "it runs just fine."

I recognize the additional cost and its impact on the billfold - I'm just a working guy, not particularly affluent, and now retired. But if the added cost of premeium fuel creates an undue strain on your economy (or ego) perhaps you bought the wrong car.

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There is a reason that they designated premium fuel.
For Volts, yes, mostly long term storage of fuel and gen 1's over compensating on everything. For those other brands, ha, its just marketing so the Karen's of the world can look down on folks buying cheap gas. Part of owning a vehicle is status to some folks. A $2000 bottle of champagne gets you just as drunk as a $4.99 bottle, sure it may taste a little better, but not enough to justify its cost.
 

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Yep, I come from the ridiculous big turbocharger worlds. 93+ was the name of the game. But, since running Premium on Gen1 Volts was complained about, I'm surprised to have see such a change on the Gen2. Normally, most naturally aspirated cars don't have much of a benefit to running higher octane rated fuels.
The Volt (at least Gen 1) is very weird about throttle handling and almost all the ICE-running time is spent with the throttle completely open and RPM constrained instead by the generator draw-off. I've often wondered whether that greatly-increased air availability would contribute to pre-detonation and whether that's part of the high-octane recommendation. But I also don't know that Gen 2 is any different, or if Chevy just learned enough to decide that it wasn't as big a hazard as they thought it might be and eased the requirements. (But might still benefit...)
 

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I have a 2013 Volt with 70K miles on it, most of which have been on the plug. I live in Denver, the "Mile High City" and often go into the mountains with it. The Gen 1 requires 91 octane gas but at higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline with most engines. E.g., our other car is a Toyota RAV 4 hybrid requiring 87 octane but I've run it on 85 octane for a couple of years without any knocking or negative effects. But, GM has been very specific on this issue saying that less than 91 octane will damage the engine. So, is there a Volt owner on this forum who lives at a similar high altitude who has used a lower octane gas in the Volt where it has not damaged the engine? That is, someone with a 2011-2015 Volt.
The owner of the "Sparky" volt (probably a 2012) ran for over 400,000 miles in his Volt with regular grade gas. As someone else said, the timing will be retarded so as to not damage the engine. The ultimate output will be less and the gas mileage will be less. I have done the gas mileage experiment and have found it to be lower with 87 unleaded. However, the cost/mile is maximized with regular and not premium gas where I live (Texas).

At higher altitude the maximum output will be achieved at an octane less than the recommended 91. I'm sure I could do a calculation to determine that, but I'm not going to. I'm sure that 88 would probably perform just fine in your Volt in Denver.

I run regular gas (87) in Austin around town. Perhaps on the highway if I thought I would need more power, I would bump it up to premium, especially if I needed some passing power on a 2 lane highway.

I have 160k miles on my 2012 Volt. Don't overthink it. Do what you want to do. You aren't going to damage the engine of a modern naturally aspired car with lower octane gas.
 

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When I had my gen1, I ran regular in it the few times it was used on a long enough trip to use the fuel. We did always have premium in it when it was running on mostly electric. Premium fuel can sit in injector lines for a lot longer without deteriorating. That same engine is used in other models that don't spec premium fuel.
 

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When I had my gen1, I ran regular in it the few times it was used on a long enough trip to use the fuel. We did always have premium in it when it was running on mostly electric. Premium fuel can sit in injector lines for a lot longer without deteriorating. That same engine is used in other models that don't spec premium fuel.
While the engine was in a car that listed 87 octane, there was a KRD - 91 Octane code on the car's code list.
 

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I have a 2013 Volt with 70K miles on it, most of which have been on the plug. I live in Denver, the "Mile High City" and often go into the mountains with it. The Gen 1 requires 91 octane gas but at higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline with most engines. E.g., our other car is a Toyota RAV 4 hybrid requiring 87 octane but I've run it on 85 octane for a couple of years without any knocking or negative effects. But, GM has been very specific on this issue saying that less than 91 octane will damage the engine. So, is there a Volt owner on this forum who lives at a similar high altitude who has used a lower octane gas in the Volt where it has not damaged the engine? That is, someone with a 2011-2015 Volt.
We have a 2014 at 6,000 ft in New Mexico. We use 86 octane almost always and have had zero problems.
 

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The manual stated to use 91 top tier in our 2012 and 2015 Volts, and that's what we did. Most of the miles on the battery, so the few dollars more did not bother. We use 87 top tier in both the 2018 Volt and the 2017 Cruze Turbo, because that's what the manual says. No problems, and I'm not looking for any!
 

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I have a 2013 Volt with 70K miles on it, most of which have been on the plug. I live in Denver, the "Mile High City" and often go into the mountains with it. The Gen 1 requires 91 octane gas but at higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline with most engines. E.g., our other car is a Toyota RAV 4 hybrid requiring 87 octane but I've run it on 85 octane for a couple of years without any knocking or negative effects. But, GM has been very specific on this issue saying that less than 91 octane will damage the engine. So, is there a Volt owner on this forum who lives at a similar high altitude who has used a lower octane gas in the Volt where it has not damaged the engine? That is, someone with a 2011-2015 Volt.
You have it backwards . Less octane is needed at higher altitudes and cooler terperatures. I ran 87 octane dozens of time in hot weather too.
 

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Once upon a time, I did do a couple of tanks of regular, but found that the $/mile was no better on regular than premium. I don't have my original numbers to share anymore, but regular was pretty definitively not better due to mpg loss.

Now I live at 7000ft/2100m elevation, often go over a pass at 9000 with moderately steep approaches (5+% grade?) but 55 or 60 speed limits. I.e. takes quite a bit of power to move up that grade at those speeds. If conditions are just right, my 2013 can make it from home over the top on a single full battery. But if I miss, and it has to go into CS, it's really anemic up there at 9k, even on 91 octane. It can hold ~55 mph with a medium high rev, it's loud and annoying and that's my "penalty for losing the game", but it's not a big deal.

I once had to do something similar with a mostly regular blend in the tank due to the only gas station on the route being out of premium. The anemic feeling was about 10 times worse. Engine was revving to what I assume was its maximum RPM (didn't have an OBD reader hooked up that day so I don't know an exact figure) and I could only hold about 40 mph up that hill.

So, for me and my subjective experience, the tiny amount of gas cost savings does not outweigh the perceived power loss, nor the probable extra wear and tear, oil life loss, etc from having to run the engine harder on regular gas.
 

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Some might think I'm insane, but I splash mix 87 and E85 so a full tank has about 2.5 Gallons of E85 in my 2015, or at least I did when I was using it for a 57 mile each way commute. I wouldn't dream of doing that if the car hardly ever used the ICE since E85 doesn't store well. I can't comment on the high altitude side, but it seemed like a good way to get the required octane while actually spending less than normal 87 costs.
 

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I have a 2013 Volt with 70K miles on it, most of which have been on the plug. I live in Denver, the "Mile High City" and often go into the mountains with it. The Gen 1 requires 91 octane gas but at higher altitudes, the air is thinner so you can actually get by with a lower octane gasoline with most engines. E.g., our other car is a Toyota RAV 4 hybrid requiring 87 octane but I've run it on 85 octane for a couple of years without any knocking or negative effects. But, GM has been very specific on this issue saying that less than 91 octane will damage the engine. So, is there a Volt owner on this forum who lives at a similar high altitude who has used a lower octane gas in the Volt where it has not damaged the engine? That is, someone with a 2011-2015 Volt.
I am not an engineer and I have a generation II Volt, but I also live at 5,000 ft. and drive to higher elevations frequently. I have been running my BMWs, that also require premium fuel, on mid grade fuel for years without any adverse effect. My understanding is that we can safely use fuel that is rated at two fewer octane points at 5,000 ft. However, this does not apply to turbo-charged engines because forced induction overcomes the lower oxygen levels.
 
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