TunedRX300

Good for you, why not try race fuel that has octane of 100, that is "ultra premium", not cheap, and certainly performance driven - well to SC and turbo engines.

dmc888

Don't forget lexus also recommends doing oil changes every 5k.

I wonder why there are alot of oil gelling issues.

Campbell

Interesting. Please explain how you obtain more hp from a higher octane fuel. Even if it is "Not much."

I will say that when I first got involved with motors I thought the same way. Unfortunately, the facts did not support this understanding.

So I pose to you this: How will the RX330 get more hp from using a higher octane?
Not trying to bust your nuts, I just want to either be schooled again or help you understand the concept of octane.

Campbell

In the medical world we call that 'The Placebo Effect.'
If it does no harm to your car, you can afford it, and it makes you feel better, Go for it.
But it isn't necessary.

NeverSatisfied

It hasn't been too long since I filled w/ 87, but so far so good! Saved a few bucks by doing so...

Ziggy09

racefuel great idea! right after a supercharger and some 26" Spinnas bling bling

HarrierAWD

Only if you dial in too much boost. Most supercharged engines will work fine with premium 93/91 gas.

jaydunn

If the octane is too low the knock sensor and the computer respond by retarding the timing. Because of this less peak horsepower is available. Thus a car designed to use 93 will still run on 87 and most people won't notice the difference. However, there will be lower performance at the margin and usually lower mpg.. This applies only to a high compression engine designed for 93. For the average grocery-getter you're just wasting money with the 93.

I kept long-term records with my previous car-an Acura TL. It would average >24mgp with the 93 but only about 22mpg with the 87. The performance difference was minimal but noticeable.

Campbell

The knock sensor is effectively useless once engine noise increases with RPM.
To think that an engine is designed to run 87 with the fact that it will knock and the knock sensor will retard timing just doesn't sit well.
The knock sensor is there to help should pre-ignition occur, but not for continuely regular driving conditions. If the engine requires 93 then it should be in the manufacturers fuel requirements for that vehicle.
Cyclinder pressure, air-fuel ratio, ignition timing, and temp all play a part in when pre-ignition will occur. (there are other factors as well.)
Was your TL requiring 87 or 93?

Rockville

The higher the Octane the higher the burn temperature of the Gas. We are recommending Premium (91 Octane) on the newer engines such as the RX330, ES330, GS300 etc. All of the Lexus will run on 87 Octane if needed provided you don't mind the drop in performance. The older ES300's and RX300's were fine with 87 Octane. My wife uses 87 Octane in our RX300. I still like Premium...go figure.

TunedRX300

RX300 is recommendated by Lexus for octane rating of 87, not 91.
The person who started this thread indicates "Lexus 04 RX330 manual recommends using 87 octane rating fuel and above". What is RX330's recommendated octane rating? Please check your owner manual and don't post if you are not sure.

jaydunn

[QUOTE=Campbell]The knock sensor is effectively useless once engine noise increases with RPM.
To think that an engine is designed to run 87 with the fact that it will knock and the knock sensor will retard timing just doesn't sit well.
The knock sensor is there to help should pre-ignition occur, but not for continuely regular driving conditions. If the engine requires 93 then it should be in the manufacturers fuel requirements for that vehicle.
Cyclinder pressure, air-fuel ratio, ignition timing, and temp all play a part in when pre-ignition will occur. (there are other factors as well.)
Was your TL requiring 87 or 93?[/QUOT

The TL manual rec. 91 octane but said 87 would do no harm but result in "reduced performance". I used 93 mostly since it gave the best mpg for that specific car.

Campbell

[QUOTE=jaydunn]I agree with what you show as an increase in MPG using the higher octane. I have seen this in some select cars. It's something you have to try in each individual car. Having long term logs of MPG is a great way to show that.
For example: 89 Maxda 626 2.4L. A gain in mpg was seen going from 87 to 89; however, going to 93 did not show any increase, infact a very slight decrease, not that it was significant thou.
Again, I believe that it depends on the car. Now as for added performance, even if a car was built and safely tuned for 89 octane and you choose to put in 93 there will not be a performance increase. Furthermore, the only way to measure a change in HP so small is via multiple runs on a dyno. Hence, if there was an increase (which there isn't) it would be so small that "thy'o butt-dyno" will not notice it. PLACEBO. The performance gain seen by going to lower octane isn't noticable, but the $$$ are. We aren't talking big differances here. Again, higher octane will allow you to tune more power. Not changing any parameter or variable, octane 93 vs. octane 87, 93 will not give you a gain in HP. Having said that, if your car is detecting knock at low RPMs then it will retard the timing and a loss in power will follow. But again, most manufactures detune or do not tune to the most power possible because they need a safety margin.
If you still hold to your theory then treat yourself. Run the gas tank down and find a gas station that has 110+ UNLEADED. ****WARNING: Some stations have high octane but it is leaded. Be sure it is unleaded gas, your cat and O2 sensor will thank you.***
If the theory you have holds you should have remarkable power results. I've tried it and found no differance in a car tuned for 93. This car runs with a small margin of safety. (98 Acura GS-R w/ many upgrades)
So spend $5 a gallon (15 x $5= $75) and tell us what you find. If the RX runs it's butt off, then I accept I'm wrong and it's back to learning agian.

I'm sure some might be wondering (maybe), but the RX330 is the wife's car and she only puts in 93. The extra cost is worth it for the silence.

Lil4X

I run 91 (or 93) octane in my 330, and although I've posted this story before, my most recent experience makes me believe even more that my choice was, for me, a good one. The reason to go to premium fuel is not for power, for there is little or no detectable difference in the two grades that my finely-calibrated "butt dyno" can detect; but a question of response. When I bought the car, the service advisor, whom I'd come to trust on issues with my 300, told me the following:

While the RX 330 does quite well with any grade of fuel, thanks to the ECM and knock sensors, the fuel-air maps and spark advance curve were optimized for 91 by the factory. That doesn't mean that lesser grades will cause mechanical, performance, or drivability problems, but there may be other effects, YMMV. Let's set the scene:

I'd been having some initial problems with the shift algorithm. Having taken delivery of one of the earliest RX330s, I had the new software flashed to the computer, and while it helped, it didn't solve all of the problems. Shifts were sometimes jerky, although the new software solved the "hunting" problem. At some combinations of road speed and throttle position, calling down to the engine room for more turns occasionally produced a jarring downshift.

My service manager told me he had a new RX too, and that these problems disappeared when he switched to 91octane fuel. His explanation, backed by the techs at the dealership, was that the programming of the ECM "expected" to see a certain spark advance curve, but when the knock sensors detected the first rattle of pre-ignition, they would dial back the spark advance almost instantly to stop the knock.

Despite the fact that the time interval is very brief, only one or two revolutions of the crank, this sent a confusing signal to the transmission, first getting power, or at least a warning that power was being ordered up, then seeming to get a brief "lift-throttle" before the shift could be executed. The result was sometimes (not always) a hard downshift as the transmission and engine signals were in brief conflict with the actual torque delivered.

Whatever the case, I begin to use 91 octane religiously, and after resetting the transmission memory (by disconnecting the battery for 30 seconds) have not experienced the "shifting" (more properly, timing) problem since. Would an occasional tank of 87 hurt? I doubt it, but for a few $ a month I'm getting a silky smooth-shifting transmission.

If you've had some rough shifting problems, try a few tanks of Premium (after resetting the transmission memory). It might work for you too!

stllex88

I have noticed a 1-2 mpg drop when using 87 as opposed to 93. I beleive I have a consistent enough drive pattern to accurately judge. Since I get gas as Costco, I don't always pay the typical full premium price. Many times Costco is only 12 - 15 cents over regular. I paid for the car. I'll pay for the premium gas.
I interpret the manual to mean the car is tuned for premium, but will run on regular, albeit at a slighty lower performance level.