Although I have tried a few gasoline brands since I got back from Mexico, I've been sticking to Chevron for the past 2 months or so though I have given some other brands a try, but Chevron seems to run the smoothest for me.

I went by quickimart at a Marathon station and noticed they advertise putting STP additives in it.

 

i use 87 in my 2005 rx330. i usually put whatever is the cheapest around. its usually valero or arco, sometimes costco. i get the same mpg no matter what goes in. now, if this was a 911 turbo, evo Mr, Impreza WRX sti, i would not hiestate to put 91 or higher. my car doesnt do anything unusual and doesnt have any weird smells even when i put in the "gasp" 87 octane.

 

possibly. depending on driving styles and how the year rx is programmed, you might get away with 87.

But more likely, it is knocking a lot and you do not hear it. In an RX is is going to be pretty muffled. Try flooring it going up hill and listen for a kind of crackling noise. If it is knocking a lot, you will blow your engine.

 

I live at 8700 ft and use 85 octane in my RX 350. No pinging and get 24 mpg with every tank- (all highway miles). I might think about higher octane if there was any oxygen up here, but given the air density at this altitude it just isn't needed.

Dave S.

 

You are lucky in that regard. Although the fuel injection system compensates somewhat, you are probably running a RICH mixture of fuel to air. That results in a cooler exhaust gas temperature, which means less tendancy for knocking.

You also probably produce fewer horsepower than I would at nearly sea level, so in a way it is a little like having a "fuel economy engine" in your lexus--less gas used.

Still, I would be careful if I tried to haul anything big.

 

Just finished a 1,400+ mile trip from Washington to Montana and return. Premium fuel all the way and averaged right at 24 MPG, and that's with cruising at 75/80 MPH on the flats, bucking some very stiff headwinds, and crossing several fairly high altitude mountain passes. The RX performed quite admirably, as was expected. Saw a pretty vast range of fuel prices, with Montana having the cheapest, Idaho second, Washington quite a bit higher and our home area of Washington the highest. Still, given the temperatures we encountered (97+ on Wednesday and stayed in the 80’s for most of the trip) the RX managed to pull that kind of mileage with the A/C running full time. Would have hated to be climbing the passes without max performance from the engine had we been running regular (lower octane) fuel.

 

I agree with you there.. plus nowadays most engines have a knock sensor and retards/advances timing if Im not mistaken. For a Turbo car.. totally different story.

 

good thing someone does. well actually my mechanic who also owns a 2005 rx330 said that it is a complete waste of money to put anything more then 87 in it. even the service advisers at the local dealer said that too, but also said that telling people not to put higher octane in their luxury vehicles make some of their customers heated.

 

It seems people are missing the logic here:
1) lower octane under some conditions makes engine knock
2) If engine knocks, the computer retards the spark
3) Retarding spark reduces fuel efficiency
4) Lower mileage results

Another caveat, if engine knocks, and it takes a few seconds to retard the spark, if that happens over and over due to poor octane it will crater your piston heads.

These are all facts and quite indisputable.

What WOULD be an interesting discussion would be on the nature of the knock sensor in the RX.

How quickly will it engage and retard the spark? .1 seconds, 3 seconds? Too slow and you will eventually have engine damage.

How quickly will it reset itself when the knocking stops? Like if you are knocking going up a mountain, as soon as you crest the peak and start going down the other side, will the spark advance in 10 seconds and get back your fuel efficiency, or do you drive around for the next 5 hours with a retarded spark? From some of my experiments with low octane, it seems like it takes many hours of driving to reset to the original spark advance.

 

Biff my friend,you didn`t know that toyota`s pride,the Lexus is a luxury car?....

 

I didn`t know Citgo was a top tier fuel?

 

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Old 07-29-08, 01:16 PM #1
lexus114
Lead Lap

Join Date: Aug 2007
Location: pennsylvania
Posts: 710

Default Lexus reply to me re;fuel octane
Recently you submitted a question to the Lexus Customer Satisfaction Department.

Thank you for allowing us to be of service to you.


Subject
OCTANE FUEL

Discussion Thread
Response (Jaret Minami) 07/29/2008 09:10 AM
Dear Mr. McArdle:

Thank you for contacting Lexus Customer Satisfaction regarding the recommended gasoline for your Lexus RX. We appreciate the time you have taken to share this communication with us.

Lexus recommends using select premium-unleaded gasoline with an Octane Rating of 91 or higher for optimum engine performance. However, if such premium type cannot be obtained, you may temporarily use unleaded gasoline with an Octane Rating as low as 87. Your vehicle will operate on an octane rating of 87, but might experience lower performance and engine knocking. You may also refer to the last page of your owner’s manual for more information regarding the recommended type of gasoline.

If you require further assistance, please contact Lexus Customer Satisfaction at 1-800-255-3987, Monday through Friday, 5:00 a.m. to 6:00 p.m., or Saturday, 7:00 a.m. to 4:00 p.m., Pacific Time.

Sincerely,

Jaret Minami
Lexus Customer Satisfaction
Customer (Ryan R. McArdle) 07/29/2008 08:01 AM
My RX manual states select 87 octane fuel,for improved vehicle performance,select 91 octane or higher.My question is;what is the ecm calibrated for? Can I safely use 87 octane fuel? I can not seem to get a straight answer re;this subject.Any help from you will be greatly appreciated.
Sincerely,
Ryan R. McArdle

**Just thought some of you may get a little kick out of this.**
I e-mailed Lexus to try and get a once and for all answer re;octane.This is what I received back from them.

 

It's not, my mistake. Here is the TopTier list of retailers.
http://www.toptiergas.com/retailers.html

 

Folks, it's just (basically) a Toyota Camry with a fancy cover. (duck and cover. hey stop throwing tomatoes!) 87 should be perfectly fine for a 2004 of either flavor, IMO. Toyotas are efficient enough to adjust and run properly for the gas, so they avoid knocking.

I have found very little difference between 87 and the higher octanes that have more octane added (to retard the efficiency of the gas, and prevent premature explosion)

Mine has never knocked or pinged, as far as I have noticed.

If it makes ya feel better, though, that's perfectly OK too.

This is just my own experience after driving it more than 4 years, and I hope you don't mind a different opinion. If it was a different model or brand, my opinion may be different. I just don't think the mileage difference will be noticeable, in this case. The savings per tank is about the cost of one gallon. ($3.60 or about 22 more miles range)

This Camry/RX engine was probably designed for 87.

 

as soon as the knock sensor (KS) detects knock, it will send the signal to the ecu. the ecu then monitors the amount of knock via the KS in a given amount of time. if knock exceeds the threshold, the ecu pulls timing. the ecu will keep that timing out until a given amount of time has passed (a couple drive cycles at least) before it starts to give timing back. if it does give timing back and detects any knock, it will immediately pull it back again.