Rx900

THAT is a real gas saver

LexusChris

iTrader: (1)

Actually the only premium vehicles I believe are the IS, GS, LS, SC and the regular include the ES, RX, GX, LX from what I saw in www.fueleconomy.gov

Rx900

IS is premium?? I'm kinda surprised if that's true!

flipside909

Why are you surprised? it's a high compression 10.5:1 motor. Same N/A 2JZ-GE VVT-i found in the GS300, SC300 and Supra.

Lil4X

As I understand it from my service manager the 3.3L's ECU advance curve is mapped for premium fuel. If a lesser grade is run in the engine, the knock sensor simply dials back the advance to optimize performance for the fuel available. While the difference in RWHP is probably undetectable to the butt dyno, there may be some throttle lag (most noticible at shift points) as the ECU quickly recalculates the advance. "Quickly" is the operative word here.

Regular fuel or a mid grade is perfectly OK from the standpoint of engine durability. If an RX will run on Pemex (Premium hopefully, Magna otherwise), it should be able to run on anything (providing it is at least strained first).

IMHO the difference of a dime a gallon or so is not a deal breaker - at least after shelling out for a Lexus . . .

krpster

FYI - at the plant it gets filled with regular

dhamaka127

I was wondering why the computer is rated for 91 octane because that octane level is hard to find around here. So I have been putting in 93 octane. My other choices are 87, 89, and 93. I have been trying to find a place that has 91 octane but didnt seem to find any. Does any one know of any way of finding places by a websearch? or somehting?

I own a 2004 RX 330 that i just got May 2006

Frankr66

i get better gas mileage with premium

so for me its not worth running anything less

tfischer

If you can't find 91, (and I can't find it either), remember that you can mix grades in your tank. Very often this is what the stations do, as they usually have only 2 grades in the big tanks, and the pumps mix those two different grades in various proportions to get the desired octane output.

I often fill it up with 98, then at the half way point, fill it up again with 93. Now I have a tank of 91. Be sure to slam on the brakes to be sure it is mixed well.

Nostics_RX

Hmm....a 98 and 93 you get 91...fuzzy math!! But I know what you're saying. Just curious, is there a disadvantage of filling it up full of 93 octane besides making a small hole in your in pocket??

tfischer

I'd like to try a tank of 98 sometime.

Obviously, I meant to say mix 89 and 93, and I think you would get 91, although math was never my strong suit.

There is no disadvantage to using 93 (or even 98 if you can find it) in a car designed for 91. Extra octane is just not used and is burned off, with no extra power or performance. It's wasted. Lower octane causes the computers to retard the timing, which does reduce performance.

If a car is designed for "regular" there is no advantage to using "premium," providing that the premium does not also contain detergents or other stuff that the regular does not -- although it is my understanding that all major brands have all the same additives in all grades (since they mix them in the pump anyway).

Lil4X

"Octane rating" is actually a measure of the burn speed of the air/fuel mix. Higher octane actually burns slower to allow higher compression without premature detonation. Higher octane fuel in itself doesn't produce any additional power, but allows a higher compression ratio to be employed . . . which does.

TunedRX300

Lil4x is right, higher octane rated gas is less volatile than lower rated one. It allows the gasoline to hold explosion until higher compression is achieved. The problem of putting obscenely high octane rated fuel in a relatively low compression engine is that gasoline is never completed burned off since the engine can not achieve the higher compression. Unburned fuel = unreleased energy, guess where these unburned carbon go to? Right down the exhaust valve and rest peacefully in the catalytic convertor.
Talk about hitting into a triple play: paying additional $ to get less performance and clogging up the cat. That is a extremely bad at bat to kill a rally

USLEX

If you want the official position of Lexus, I would suggest you contact them and ask. I think they would respond that you have to go Premium definitely.

Furthermore, if gas prices are that much of a concern to you I suggest getting a Prius (2005 fully loaded) or a RX400h. My Prius got 45 MPG on average. I could go a week and a half before I had to fill up. From memory, I think the RX400h gets 28 MPG hwy.

No offense but most ppl that buy a Lexus do not weith fuel economy as the to priority. For me it was Looks, luxury, dependability, value and MPG is a bonus.

Lil4X

Worse yet, by putting unburned fuel into the cat, you could achieve an "afterburner" situation and REALLY overtemp the cat.