Originally Posted by satiger

Doublebase, diesel and gas fuel uses the same pipeline. You're spot on, that's what my concern as well. Except for rentals and loner cars, I don't go to un-branded stations. Federal law stipulates octane level to match or exceed advertised number at the pump and on extreme weather places to have additives to stabilize the fuel (freezes in gas lines or vaporizes etc).

Another interesting point is, good time to pump gasoline is in the morning hours (or when ever temperature is low). Fuel expands due to temperature. Pumping during hot afternoon will result less actual volume than what you see on the pump meter!. Volume difference due temperature variance are adjusted by systems during pipe transport and rack terminals but not at gas pumps!!!.

Originally Posted by Lavrishevo

I understand where you are coming from. In general, it is good to update the ECU to the latest firmware. Often there are other improvements Lexus makes that they don't advertise including shifting of the transmission and even tweaks to fuel maps for better efficiency. Would not hurt to call Lexus cooperate and see if they will do it for free. You will be surprised how often being nice but insistent will work for you. My dealer takes care of me all the time because of the relationship we have built. They also checked and confirmed my ECU had been updated without a charge. I would personally do it. I don't think you have anything to loose.