Do you use 85 or 91
 

My mom recently got a GX and is putting 85 in it. The dealer says it's ok, but who hear actually uses 85 in their GX? In my IS I use 91 exclusively, in my old man's Vette he use 91 exclusively, why not use 91 in the GX? Does it really make a huge difference, I've heard for the long haul it makes it rougher on the engine?

Isn't the minimum 87??

87, 89 or 91
 

in California
use 89 in mine

I use 87 in mine, did use 93 but it just burnt way more and I was tired of filling up so often.

The only way your gonna shorten the life of your engine with fuel/gas is if the engine knocks or pings, other wise if the engine is quiet and sounds like it should with regular maintanence the truck should go 200k plus but your mom will probably not even keep it that long;)

So the octane ratings in Colorado are 85/regular and 91/premium, anything in midgrade.

Denver have you ever tried 85 in the IS, I know of all the car manuals I read about what gas to use the IS300 is the only 1 that says if you experience knocking or pinging then use a higher octane, my ES300 does not say that and runs the same on 87.

Gas door on my IS says 91 only, so far in the three years I've had, it has worked. I"'m only going to have the car for another few months so it's not really a debacle. I'll tell my mom the whole engine knock, thing, thank you for the advise!