Quick poll: do you use regular or premium gas in your RX300?
08-28-01, 09:10 PM
#16
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I've been running my 2001 RX for its first 3200 mi. on regular... just tried some 93 on a long trip back from Vermont to NY. Didn't notice ANY appreciable difference in performance, and strangely, the mileage did get a tad worse. Dealer suggested using it once every couple of months, don't know why (does 93 clean fuel injectors better?) Anyway, I agree with those who say the extra $$ may not be worth it...
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08-28-01, 09:20 PM
#17
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Everyone says to me use regular because there isn't any difference, but i do feel a little more kick when i use a higher octane..... Maybe it's in my head but it works for me.... I'm not changing enless theres some real proof that i'm wrong... Everybody playing a guessing game as of now... But thats ok I love you all....
08-29-01, 06:24 AM
#18
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It is a myth that if regular-grade fuel is good, premium must be better.
In reality, as some of you have already stated that the RXs are designed to run just fine on regular-grade (87 octane) fuel. A higher octane number doesn't mean that your vehicle will perform better. It simply means that it's more resistant to engine knocking or pinging. Use the octane grade that's recommended in your vehicle's owner's manual (87). Filling up with a higher grade is usually a waste of money.
In reality, as some of you have already stated that the RXs are designed to run just fine on regular-grade (87 octane) fuel. A higher octane number doesn't mean that your vehicle will perform better. It simply means that it's more resistant to engine knocking or pinging. Use the octane grade that's recommended in your vehicle's owner's manual (87). Filling up with a higher grade is usually a waste of money.
08-30-01, 10:05 AM
#19
Lexus Test Driver
I use 87 per the manual.
With regard to pinging and the ECU, yes the pinging occurs first before the ECU retards the timing. There is a knock sensor implanted in the cylinder wall that monitors for this sound. It is so sensitive that you would not even hear the slightest ping.
If the ECU does not sense any ping at a particular engine load, temperature and throttle position, the ECU allows the timing to go back to its factory optimized default. The default is programmed with the 87 octane fuel characteristics.
If there is a 91 octane in the tank, it is simply wasted. A lot of people doesn't know this but a 91 octane gas burns *slower* than an 87 grade. And that's the reason why an engine with a high compression ratio would knock if you put in an 87 octane, but would run fine with a 91. Knocking is similar to explosive burn, as opposed to accelerated burn.
Now, imagine what a aviation fuel is like. It has a very high octane rating and the highest ones are almost like kerosene! The octane rating, or antiknock quality, of AVGAS is expressed in terms of lean and rich ratings of the fuel. AVGAS is available with lean/rich ratings of: 80/87, 91/96, 100/130 and 115/145.
For the LS400, I only use 91, as per the manual. Once, my wife filled it up with an 87 octane. The car drives fine at constant speeds. However, when pressed hard, it doesn't accelerate as quick as when a 91 gas is being used. Clearly, the ECU was retarding the timing.
With regard to pinging and the ECU, yes the pinging occurs first before the ECU retards the timing. There is a knock sensor implanted in the cylinder wall that monitors for this sound. It is so sensitive that you would not even hear the slightest ping.
If the ECU does not sense any ping at a particular engine load, temperature and throttle position, the ECU allows the timing to go back to its factory optimized default. The default is programmed with the 87 octane fuel characteristics.
If there is a 91 octane in the tank, it is simply wasted. A lot of people doesn't know this but a 91 octane gas burns *slower* than an 87 grade. And that's the reason why an engine with a high compression ratio would knock if you put in an 87 octane, but would run fine with a 91. Knocking is similar to explosive burn, as opposed to accelerated burn.
Now, imagine what a aviation fuel is like. It has a very high octane rating and the highest ones are almost like kerosene! The octane rating, or antiknock quality, of AVGAS is expressed in terms of lean and rich ratings of the fuel. AVGAS is available with lean/rich ratings of: 80/87, 91/96, 100/130 and 115/145.
For the LS400, I only use 91, as per the manual. Once, my wife filled it up with an 87 octane. The car drives fine at constant speeds. However, when pressed hard, it doesn't accelerate as quick as when a 91 gas is being used. Clearly, the ECU was retarding the timing.
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