85 octane in highlander hybrid

[jasims]

I live in Colorado where due to the altitude regular unleaded is sold as 85 octane instead of 87. The Highlander owner's manual says that a minimum of 87 octane should be used.
I'm trying to find out whether there is a negative impact of using 85 octane at altitude.

I haven't been able to get any solid info from Toyota and got conflicting answers from the dealers.

Anyone have any insight?

Thanks,

john

[vonk]

Due to the higher altitude, your effective compression ratio will be somewhat lower. Therefore, you should be OK with 85 octane. However if you ever detect any audible pinging under heavy load, switch to the next higher octane available.

[nodrogkam]

^ yeah what he says is correct. PLUS why not just ask your dealer? I would go with a higher octane anyways, especially if you travel to lower elevations a lot.

[jasims]

Well I finally got an answer to my online inquiry at Toyota's web site.
They are sticking to their guns and simply said back that 87 octane is the lowest rating that should be used in the vehicle. They didn't really address the issue of operating at altitude, just quoted from the owner's manual. 87 is sold as mid-grade in CO, so I guess I'll keep using 85 and save the money unless I hear any pinging. It's too bad they don't have any specific details about operation at altitude.