Here's an interesting thing...
Back in 2011 I started looking to buy a Buick LaCrosse. I wanted the V6 engine, they only come with 6 speed automatic trans. The top 2011 model was called the CXS, had a 3.6L V6, made 280 HP, and required premium fuel. I'd never owned a car that required premium fuel and wasn't super stoked about that. It's stated MPG: 17 City / 27 Hwy.
The model year was switching so I waited to see if I would buy an 11 or would there be any new or improved features for 2012 that would sway me. Well... for whatever reason they changed the top trim line name from CXS to Touring, the 3.6L engine now made 303hp, and the fuel was now reduced to requiring only regular 87 octane! I bought the 2012 Touring and have never put anything in it other than 87 octane. It is a DI engine, runs 0-60 in around 6 seconds. It's stated MPG is the SAME: 17 City / 27 Hwy. (I believe the 2012 Camaro V6 made 323 HP and also ran on regular?, rated at 18 City / 28 Hwy for the Auto?)
The shape of the LaCrosse didn't change. I don't know how they were able to to get the extra 23 hp and reduce the octane requirement (maybe it a totally different engine, or some of the internals?)
Because I bought the 2012 Buick over the 2011, I've been saving $0.60/gallon over the previous car. If I drive it 100,000 miles (currently has 72k on the odo) and get an average of 20mpg, that's 5,000 gallons of regular gas, I'll see a savings of $3000 over the 2011 car. It's not enough to retire on but's it's something. More power, for less money
Side note: My brother has a 2013 Lexus 350 GS AWD 3.5L V6 which makes 1 HP more (304HP) and his requires premium - ouch.
We've now added a Camaro V8 and we knew going into it that it required premium fuel. I love the power and feel like the premium fuel must be the cost of making the 455 HP. What I would love to know is... How much power could they make using the same engine but tuning it to run on 87 octane?
I'd probably be ok losing a few HP (but keeping the V8). If my old man LaCrosse can make 303 on regular, I would imagine you'd still be over 400hp running regular in the V8.
Rather than eeking out a 1-4% gain or loss, I feel like the Camaro could essentially increase it's fuel efficiency by up to 25% (the cost difference between prem & regular) if they could just run the V8 engine on regular. If instead of 455hp, it ran something like 400-425hp, it would probably be fine with me.
Even better would be if they let you choose on the fly. A button on the dash that sets some tuning for what octane you're running (if that's even possible).