BOWTIE 3

We've always used 92-93 octane fuel in our 2000 RX 300. Even though the dealer told us we could use regular or the mid-grade fuel, I've always understood that the engine has " knock sensors " that retard the ignition timing when a lower octane fuel causes a gas knock, therefore reducing engine performance. It was explained to us that if a higher octane fuel is used, then the engine would perform as designed. Every once in a while we hear a " timing knock ". We've always used Shell or Citgo fuel in the RX and my ' 01 Silverado and generally never have a problem. Is this a problem typical of RX's or should I have the dealer check out the engine controls? The car has 48,000 miles, gets dealer service, and has never failed to provide excellent service. Any input from the forum members would be appreciated. Thanks.

NeverSatisfied

I say, just use the middle grade (89) and you'll have no problems. I was always using 91 in my IS, but after the price of gas skyrocketed (and never comes down), I started using 89 and observed no change in performance and never heard any knocking. (87 is $2.69/gallon here on Maui!?!)

mikey00

I have owned 2 RXs now and am a firm believer that anything over 87 octane is throwing your money away. But that is a whole other discussion and if you do a search you will find those that agree and those that disagree. Now back to your question. You should not have any spark knock even with 87 octane. I do hear of this problem more with the 2000 year than others. It is usually followed by the check engine light coming on eventually and one of your sensors needing to be replaced. If you do a search on this you should find info from others who have encountered the same problem.
Mike

HarrierAWD

I always use 87 in my RX300. Never a knock. Runs fine.

You may need to gradually step down the octane to let the PCM learn to retard the timing.

Or you might have some carbon deposit on top of the pistons that reduces combustion chamber size. This could happen when the octane is too high for the engine and the gas does not burn completely.

LexRexBlue

When I purchased my '99 RX Lexus recommended premium. However, about 2 years ago the car was "reset" by the service dept. to work with regular. I use Shell and it is running fine.

toy4two

My 2000 has 60k miles on it, 87 octane since day 1. Since it costs us an arm and a leg for gas in San Diego thats all she gets.

Pull your ECU Fuse for 1 minute and that will reset the ECU and it will relearn the new timing maps. If it knocks after that get it into a dealer. The V6 used in the RX is used in many cars/trucks in Toyota's line and 87 is not a problem.

If you run with the POWER button turned on all the time that may be increasing the timing causing knock.

DDLexus

My 2002 RX300 with only 47k miles is also knocking during accelleration. I not sure if the gas we bought was just junk or if the knock sensor needs to be replaced. We've been putting 87 octane in the car.

I think a trip to the dealer might be in order shortly...

BOWTIE 3

For the past few weeks I've been using Amoco/BP 89 Octane and have not experienced the gas knock. I was reading another forum about particular brands of fuels and Amoco/BP was mentioned often for solving this problem. I now use it in my ' 01 Silverado also, with NO gas knock. I thought the Lexus dealership was giving me the " run-a-round " when they told me it was probably caused by " degraded " fuel quality, but maybe they were right!

Lil4X

Sunbelt states are now getting their "summer" fuel formulations which may upset some of the "learned" behavior of the ECM, picked up over the winter. Colder climes will soon see this seasonal change as well. While the octane rating shouldn't vary much from season to season, some of the changes in volitility (lower in summer) may upset the burn just enough to cause an occasional knock or hard start. As toy suggests, just pull the EFI fuse for a few seconds and see if erasing the "memory" helps.

bizzy928

We used to put 91 in our RX . Then we gradually stepped down to 87. Been running fine every since. We did 91... then one month of 89... then finally to 87

HarrierAWD

I've been using mostly BP/Amoco & ExxonMobil 87. Never a knock. Most major brands work fine.

Some gas stations do cheat on octane. I once filled up at a Conoco in Utah. The engine didn't knock, but it felt weak after about 10 miles and gas mileage dropped to 15 mpg vs. 24-25 mpg on highway. Also had a similar experience with Diamond Shamrock.

Back in the old days, some gas stations also buy "90-day gas" from unknown sources to save money. This kind of gas can gum up your fuel injectors over time. Fortunately 90-day gas is rare nowadays due to tight supplies.

DDLexus

I took my 2002 RX300 with 46k miles to the dealer. I complained about the clunking noise the car makes during accelleration. I noted that the engine "sounds" like it is burning bad gas, but it has been this way for the last few fill-ups. They told me to switch to 91 or higher octane gas. With fuel prices on the climb, and the manual stating that the RX needs 87 or higher octane, I'm mad as hell.

I'll do as recommended by the dealer, and if the noise disappears, I guess Lexus has screwed up. They should state the car requires 91+ instead of the listed 87.

Anyway, problem was documented by the visit. Maybe when the car is still doing this outside of the warranty period I can tell the dealer the problem existed, but they didn't correctly diagnose. That's just thinking too far ahead though.

mikey00

Try another dealer or call customer satisfaction number. While I have no doubt that switching to 91 will stop the pinging, it should not be necessary. I never used anything but 87 in both my RXs and never had any problem as do many others. You may want to mention to the dealer that many others use 87 without any problems and the manual states 87. You can check that here and on other RX forums. If your RX pings on 87 it has a problem that should be fixed. The dealer took the easy way out by telling you to switch to 91.

parula

I have almost always used 87 and the cars ran fine, no pinging that I ever noticed even in hilly areas.

BOWTIE 3

What/where is the fuse # I pull to reset the computer? Does that also change the " shift-personality " of the transmission?