Octane ratings and Elevation

[S]

I live at an Elevation of 4500ft above sea level. In our reigion the highest octane fuel at the pump is 91 octane. I have been told (former petro man) that we have a lower octane rating than its sea level equal, due to air density at the higher elevation our 91 octane would be the equivalent of running 93 octane at sea level ?! (91octane @4500ft=93octane@sea level)

SO THE
At 4500ft using our 91 octane Fuel; do i need to use an Octane Booster???? Or can you confirm the lower octane at elevation is the same????

Wondering if I need to run the 91octane Tune due to the highest octane in our reigion being 91 octane......

Should we run the 93Tune using our 91octane? (correct combo?)

If petro man is correct can you start to include an explanation regarding octane ratings and elevation...Please!

[Mike_Levy]

Its well known that the air is thinner (less molecules in a given volume) at higher elevations, so you can use lower octane and get the same mixture or air and fuel molecules. You should be able to use the 93 tune, but log it to be sure. And when you come back down to earth, make sure you use either 93 octane gas or the 91 octane tune.

[lito]

Octane is octane, you can take a jar of 91octane to the moon and it will still be 91octane.

Now, at high altitude air density is lower than at sea level, so cylinder fill is lower and hence cylinder pressure, that is why you can get away with more timing at higher altitude places than at sea level. This is true with normally aspirated cars, and aprox true on supercharged cars, not true for turbo cars controlled via boost controlled with MAP reference.

So yes, you may use a higher octane rating but I would not recommended it if you can't monitor it or don't really now what you are doing, so my recommendation is to keep your 91 tune installed, you can do some test with a 93 tune if you want and see how it goes, keep an ear on pinging and see if the added timing helps the car go better to see if it worth the risks.

[S]

Thank you both Gentlemen!
I had been running the 91 Tune just to be on the safe side.(I haven't wanted to use a booster or buy racefuel...lol)
About the octane is octane, i am sure you had the idea that the Tune was more in question than 91 turns into 93 at altittude.=) the O2 is the key we can all understand that.
The gist is,,, is Octane booster required to run the 93 tune(safely)?

Sounds like it is Iffy at this point.

I guess that is the New Test.

Unforetunately i am a completely new user and have not dove into all of the monitoring capabilities. so until i am able to use the log function and understand it.... I will take "lito's" advice and stick to the 91Tune.
Thank You again!!!! (very fast response, thanks)
p.s. 2006 Dodge Ram 2500 Qd 4x4
using U7137 (new crom)

[Ill_Born_SS]

Nice truck,

Increases in barometric pressure or temperature
increase octane requirement. Increases in humidity will
lower octane requirements. Octane requirements decrease
at higher altitudes due to decreases in barometric pressure.
Many of the variables related to octane and octane
requirement can be totally or partially compensated for by the
engine control systems in most late model vehicles. For
instance, vehicles equipped with knock sensor devices allow
the engine control system to advance or retard the ignition
timing in response to engine knock. Other vehicles with
electronic engine controls employ the use of a barometric
(baro) sensor to compensate spark timing and air/fuel mixture
in response to barometric changes. The effect of altitude on
octane requirement in these late model vehicles is about one third
that of engines not so equipped.
A number of myths about octane have grown over the
years. There is a widespread perception that the greater the
octane the better the performance. However, once enough
octane is supplied to prevent engine knock, there is little, if
any, performance improvement. One exception to this would
be in vehicles equipped with knock sensors. In these vehicles,
if octane is insufficient, the computer will retard the timing to
limit engine knock. If the vehicle is operating in the “knock
limitingâ€