Date registered: Mar 2005
Vehicle: '01-E320 & 02-ST2
Location: John 15:18-19
Mentioned: 0 Post(s)
Quoted: 35 Post(s)
RE: Gas & Elevation
My old stomping grounds. (sigh) I do miss CO.
I would recommend using the octane specification from your owners' manual regardless of altitude, particularly so for an older car.
While altitude does effectively decrease the potential octane requirements for some engines (which is why in Colorado, Wyoming and SLC they have 85 octane regular) you'll note that the premium grades are still 91 or 93 octane. That's because some engines are designed for a specific octane requirement, and bumping it down based on altitude is not recommended. Besides, assuming the correlation would work and you could bump 93 to 91 or 91 to 89, then you're only saving a dime a gallon or so; it's not as though you could drop to the 85 octane stuff.
My recommendation would thus be not to risk it and stick with what the folks that designed your premium car recommend.
Take care and enjoy the ride -- at any altitude. [:)]