Toyota: Air condition System and Gasoline Octane Ratings, boat propellor, poor gas mileage

Question
I bought recently a Toyota Revo GSX Model 2001.  I am the third owner and got it last March with only 8 thousand kilometer mileage.

First, I would like to know how street flooding affect the air conditioning system.  I was once told that if I got caught in a street flood, I must shut off my aircon unit. Is this necessary, and if so, why?

Second is about the gasoline octane ratings.  My company provides free gasoline allowance for its employee, but it issues the Petron XCS which has an octane rating of 95.  However, whenever I am forced to buy my own gasoline, I use the Unleaded one which has an octane rating of 93.  Per my car's intruction manual, I can use gasoline with octane ratings of at least 90 for my Toyota engine (1RZE).  I would like to know if there is any effect on my engine with regards to my frequent changing of gasoline that I use.

Answer
Hi Dave,

Sorry it took me so long to get back to you, my computer is dying.  Sometimes it works and sometimes not. :-(

Street flooding shouldn't affect the air conditioning system in particular unless your compressor is installed lower than your engine cooling fan.  I am not familiar with the setup of the Revo, we don't have those in USA.  The main problems with driving through deep water are when the engine cooling fan strikes water and then is driven like a boat propellor into the radiator.  Also water in the air intake for the engine will cause serious damage.  Cars are usually designed with water-critical components close to the top of the engine compartment though.  Most passenger cars can handle water up to the hubs (center of wheels).

If your Revo has a "learning" ECU and an automatic transmission, changing octane ratings can cause you to get poor gas mileage and decrease performance.  My 98 Tacoma has both of these, and the ECU performs data collection and statistical analysis to fine tune the transmission shift points, timing, and other things for optimum gas mileage based on my driving habits.  Again, I'm not familiar with the Revo, but since its fairly new, I would assume it has the learning ECU.  Changing octane will not permanently harm your engine.

Hope this helps,
SherryB