Octane For A Rx330

[wankel7]

My mom just got a 04 RX330 and she was asking what type of fuel to put in. The book says 87 octane is fine. However, there is a little sentence afterwards that says higher octane yields more performance.

Ok, that doesn't make any sense. Since putting a higher octane in a car doesn't give you more power. It could even hurt power and fuel mileage.

So, the only thing I can think of is the EMS senses what octane it is buring and if it senses higher octane it changes timing to allow for more power.

So, am I barking up the wrong tree? Or is Lexus trying to support the oil industry?

Thanks !

James

[tds]

You are correct. The engine controls keep advancing the timing until they begin to sense detonation (i.e. pinging). Advancing the timing gives you more power (only if the engine does not ping).

Here is the official answer from Lexus for my RX300...same answer for RX330:

I interpret this response to mean you should be able to get an additional approx 10 hp by using 94 Octane gasoline.

Here is the response:

There is more than one "octane rating". Research Octane Number (RON) is a

laboratory rating that manufacturers generally use.

Motor Octane Number (MON) is another laboratory method of measurement. Anti

Knock Index (AKI) is the number quoted at gas stations. It is an average

of these two: RON + MON / 2

87AKI is equal to 91RON. The engine in the RX300 produces 220 hp on this

"regular" fuel. If premium fuel is used (over 87AKI or 91RON), a slight

improvement in power output is likely.

The ignition system used on the RX300 continually monitors engine knock

(detonation), and tailors spark advance to operate at where its peak

performance can be obtained. Hence, the better the fuel, the better the

potential performance (within limits, of course).

[jerryray]

I have tried different octane ratings in my rx330. I have never found any difference in gas milage or performance.

[wankel7]

Thank you for the response! I guess that does make sense. I did not know about the different ways of rating the octane.

Maybe a good time for higher octane fuel would be if you are towing a trailer and the car is at GVW?

I guess the real test would be if somebody would strap their RX330/300 to a dyno:)

James

[RX400h]

I would venture to say that if your mom is over 40, she will probably do just fine with regular fuel. My Mazda MX6 GT-Turbo's manual says the same thing; needless-to-say, I pump in super. However, if I were to sell my car to my mother, I'd tell her to use either regular or mid-grade.

[wankel7]

Indeed she is over 40:) She never will floor it. Maybe once a month. I told her to do that at least once a month so it does not build up carbon. Not even sure if that would happen with the lexus.

She had a 92 Saab 9000 Turbo before. And she put 87 in it just to see what happened. It detanated baddly. So she didn't do that again:)

However, with the Lexus it would prob do fine on 87.

I have a 91 Turbo RX-7 and I only give it 93 octane.