VSsc400

iTrader: (1)

I used 87ocane gas on my RX300 for about 9000 miles and it finally threw a check engine light.
I ran the tank down to close to empty and filled it up with 93octane and about 100 miles later the check engine light went away.
I filled the tank back up with 87 octane and it immediately threw a check engine light.
I drove till it got close to empty on that tank and filled with 93 octane... and about 100 miles later the check engine light went away again....

So I guess that means we can't use 87 octane... oh well..

I'm going to try with 89 octane in the next few weeks to see what happens.

C21Lexus

For what it's worth, I just use mid-grade on my new RX330. No light as of yet & I'm getting to 3K in my first month of ownership. Another thing I wanted to say was that my previous car (5.0 Mustang GT) would knock with 87 but 89 octane did the trick and I retired that car at 153K. I'm certainly not a mechanic or an expert on the RX engines, but I think you'll be fine with the mid-grade.

VSsc400

iTrader: (1)

how many miles on your car?
how long have you used 87 octane for(in mileage)?

I make sure to put the gas cap on tight. I've read up on that the check engine light may be caused by the gas cap not being closed tightly but this does not seem to be the problem since it does go off once i start using 93 octane gas.

I would not say a bad o2 sensor even though in another 12k miles or so i should change it (the car has 88k+ miles now)

toy4two

87 has always been fine in my RX.

You should stop by AutoZone and check out their OBDII Sensor Checker. It will tell you what the light means.

Mine was because my gas cap wasn't tight enough.

mikey00

Only used 87 in both my RXs and never had a problem. My current RX has 63,000 on it. I bet one of your sensors is failing. The scenerio usually is the engine begins to ping slightly so you use a higher octane to eliminate the pinging but finally the check engine light comes on indicating which sensor is bad.

HarrierAWD

I've always used 87 octane. Never a light.

Note that some gas stations cheat on octane rating. I found Diamond Shamrock and Conoco in Colorado and Utah are notorious for this. Some of their stations put 85 (regular) in 87 (mid-grade.) No warning light but the engine gets noticeably weak when I gas up at one of these rough stations.

ederny

VSsc,

Your vehicle is developing a problem that should be corrected. First, have the OBD II code read out as suggested. It could easily be related to one of the two knock sensors that are located on the 2 cylinder banks. Since the 3.0 liter is a high compression engine, it is essential that both knock sensors are working properly when using 87 octaine. If one of the knock sensors are soft, it may easily go south totally at any time. Only through the magic of electronics are we allowed to use low grade gas.

We don't like knock because it causes damage. In the mean while, stay with high enough octane to avoid the light from coming on.

Ed

JFlo

Not that it matters to most, but I only use premium fuel from either Shell or Sunoco. I was told a while back that other gas stations have a high concentrate of bad things for your car. (sorry for all the "technical" words) Anyways, that is what I do .... and it works good for me.

HarrierAWD

Actually, that's just advertising from oil companies. They want drivers to believe that their gas is better than other brands, so you'd patronize them. Chances are they all came out of the very same refinery in the area.

I can't recall the last time that I used Shell or Sunoco, but my Lexus runs fine on BP/Amoco, ExxonMobil, and a few others.

Traturn

With a blind dart, I would suggest that the Air Flow meter is failing.