Quality fuel is what will matter, top tier fuel works best at any octane level, consistency in the place you get fuel works too. If you run fuel from a no name place or one that doesn't add additives then be sure to use a fuel cleaner like techron. Higher octane does give your motor more HP and TQ however it is not needed.
I use higher octane in the summer as hot temps make the old girl a bit sluggish. Yes higher octane does help. It allows your engine to have more aggressive timing and fuel maps which in turn give you more power. Much of it accelerating as that is where higher octane can help.

 

I'll throw my 2 cents in , if you can find 100% gas give that a try... I find it delivers the best power/performance you can get, but it does cost a bit more, but we are talking 30 40 cents more per gallon...

 

Who would have ever foreseen the day that "pure gas" was a thing.

Seems like that movie, Robot Jox (I think) where it's a future waste land and Freon is more valuable than platinum... lol

Of course... who uses Freon any more?

 

The thinner air results in lower compression pressures in the combustion chamber, which allows for the use of lower octane gas. 85 octane gas at 5,280 ft above sea level (Denver) is functionally equivalent to 87 octane gas at sea level. Doesn't matter what the fuel delivery system is - the air pressure is lower and that affects all engines similarly. Likewise, a normally-aspirated gas engine loses about 20% of its power going from sea level to Denver. So your 300-hp truck in California or New York is now 240-hp in Colorado or Utah.

Forced-induction engines suffer less of an effect, and diesels even less so, but all engines put out less power at higher altitudes. It's physics.

I lived in the Denver area for 10 years, and also did a lot of fourwheeling above the tree line, so I'm familiar with the effect (on both carbeurated and FI engines).

 

Much of the new stuff climbing Pikes Peak is electric... No HP loss with altitude

 

The fuel I filled it with was 85 octane, I haven't and won't use E85. And I agree - not only a dumb idea to use food for fuel, but to PAY farmers to grow it specifically for that purpose when all our actual food is being imported is just ridiculous!

There is a gas station near where I live that has 91 "pure fuel" meaning it has no ethanol ... I'd need a mortgage to fill the Burb with it though, it's about $3.50 a gallon! She seems to run fine on either 85 or 87 octane. Thanks for all the replies.