Gasoline octane rating question

At higher altitudes cars require a lower octane than at sea level. (Less air, lower air pressure, lower pressure in the cylinders) In the front range of Colorado all you see for regular is 85. Same in SLC. At your altitude it works like 87 at sea level.

 

Comsumer Reports once did an article about the wastefulness of using a higher octane than needed. They suggesting trying a lower octane than required. If there's no problem (knocking or pinging) then use the lower. For example if a car's manual says 94 try 90. If 90s too low try 92. In your case, you shouldn't have any problems, but if you do try 87.

 

Tried this. Filled it up with Premium ULP and got better milage (.3l/100k) but it was still cheaper to run on STD ULP!

 

narf is right.

 

Octane rating is not about energy/gallon it is about premature ignition with compression. Do a search and you will find multiple threads on this subject. When all variables are eliminated high octane gas provides lower M.P.G. than the one appropriate for the car.