I recently moved out to Colorado Springs (elv. 6053 ft) and noticed that the octane sold at the pump here is:

regular 85
better 87
Premium 91

Everywhere else I've ever driven is usually 87, 89, 91-94. I was wondering about altitude's effect on a vehicles aspiration--namely that since there is 2/3's as much oxygen here as at sea level that the chance of running a lean condition is less. Therefore requiring less of an octane rating.

My counter-argument is that the gas stations here are getting away with (literal) highway robbery by selling cheaper gas at a more expensive price-point.

Since I normally run 93 octane and have my Cobb AP tuned for 93 I am concerned about running 91. Granted, I've already noticed the power drop-off from driving in the midwest (elv. roughly 1,000-2,000 ft) with 93, but I'm curious how much of that is because of elevation change and how much is octane change.

I'm off to Lowe's to get some Xylene and artificially boost my octane rating (1 gallon Xylene ot full tank of 91 octane gas should give roughly 94 Octane) and check on the results, but any input would be greatly appreciated.

-Greg

 

Just download a map from Cobb for your AP for 91 octane and you'll be fine.