afpj

We use to run 87 octane for our 2005 RX, Costco stuff. 87 was the minimum recommended for that RX. But using non tier-1 gas eventually led to fuel injector clog and malfunction...an expensive fix along with a decarb service. Since then we used 91 octane tier-1 gas, made a difference in power, but not so much any change in fuel economy for that car. Now with the 10RX, we stick to tier-1 91 octane, mainly for the detergents. Don't want another fuel injector replacement or decarb service. Average mpg 19 overall. Got up to 25 mpg on a long trip flat road, 70 mph, no head wind. (Have AWD) For these SUV's, wind resistance is a BIG factor.

The G Man

Yes, once it goes to the lower timing table, it will try to advance to a higher one until It sense a knock or a ping, then it will back off again. That is how it can take advantage of the higher octane gas. If it stays at the lower timing table, then 91 octance will be useless for the life of your car.
The knock sensors act so fast that you will never hear or feel that slight knock or ping, but believe you me, its there.
In the Lexus manual, it states 91 octane is require, not recommanded.

LeoDLion

I went to the 2010 manual and this is what it says on page 606:..."Premium unleaded gasoline with an octane rating of 91 or higher is required for optimum engine performance. If 91 octane cannot be obtained, you may use octane rating as low as 87...but may result in engine knocking..."

To be on the safe side, use 91 or higher. Lower octane is okay unless the engine starts knocking.

The G Man

Yes, 87 can be used in emergency, but 91 is require.

lexus114

[QUOTE=The G Man;5045953]Yes, 97 can be used in emergency, but 91 is require.[/QUOT

Wow,97 Octane huh?

lexus114

[QUOTE=lexus114;5045993][QUOTE=The G Man;5045953]Yes, 97 can be used in emergency, but 91 is require.

Wow,97 Octane huh?

jskennedy

let's assume you guys have shown me the light & i'm now using premium fuel

wasn't looking to debate the subject

how are you so sure something you can't hear/feel is actually there

is there a hidden menu feature that monitors the knock sensor(s)

DNC

Let me ask you, why would you think Lexus recommends you use premium fuel?

LeoDLion

Sorry but that is not what the quote says. It says 87 octane may be use and not for emergency only. If your engine does not knock using 87 than you are okay. If the engine knocks at 87, dont use 87.

The quote says 91 is required for optimum engine performance. It did not say it is require period. If you want to run your car below engine performance, use less octane gasoline. What does optimum engine performance means? To me it means getting the most energy from the fuel you use. To me this translates to miles per gallon of fuel usage. Therefore if you want to get the best mpg, use 91 octane. Isn't this what we have been talking about? That if you use less octane then you will get less mpg. But this should not preclude people from using less octane gasoline provided the engine does not knock. If people want to balance between cheaper less octane gasoline versus lesser mpg, thats fine with me. To each its own.

jskennedy

i honestly have no idea

would be interesting to hear their answer & not a "my dealer said" answer

my best guess would be their engine was tuned w/ premium

same as their suspension was tuned for a particular size tire

one would expect the best performance from the recommended tire size

but many like swap tires for their own personal prefs, it's an american thing




what does lexus's recommendation have to do with expecting knock exists when you can't hear/feel it

Gman stated it like it was a matter of fact

if there's a way to view this somewhere, it would be really cool

i've seen the 1 menu that shows you speed & voltage, but no knock

i've seen knock occur w/ 93 octane in another vehicle & have no doubt it's possible w/ 89 in my rx

but being possible doesn't make it so, especially w/ my granny driving style

i used to always race to the next light & drive 10mph over limit

my throttle position never goes over 20% any more

DNC

I really don't think there is any way to explain this to you. Use whatever fuel you want. I certainly don't think you are alone in the Lexus camp with your beliefs. Most people view cars as deposable items anyway. I just want mine to last as long as possible.

jskennedy

you've already done a fine job of explaining your views

you think premium fuel is the only way to go & i'm stupid for using 89 octane

i'm not telling you your wrong on either point



i do not believe my vehicle is disposable

i purchased my rx w/ a cash4clunker trade-in on my 98 jeep grand cherokee

the jeep was the 1st new vehicle i ever purchased

i told myself when i bought it i'd drive it 'til it died

my dad got 350k miles out of a chevy silverado & i was hoping to beat him

i got 11 yrs & 230k miles out of my jeep & it was still running strong as ever

i hated giving it up after it had been so reliable for so long

& knowing a perfectly good engine/tranny would be crushed

& the fact that the jeep had a perfect mold of my *** in the driver's seat

but $4500 for a vehicle only worth a grand was too good to pass up

so unless someone else offers me a deal too good to pass up in 10-15 yrs

i'll drive my rx 'til it dies

DNC

Your story is amazing.

ajs

After all the rambling responses, I’m still not sure what is the real purpose of your posting. If you are trying to get validation for what you’re doing, I don’t think you’ll find it here.

So you want to use regular gas on your Lexus, just like you did with your Jeep. Which makes me wonder, why did you buy a Lexus and not another Jeep or equivalent? You could have bought something like a Honda Pilot, or Toyota 4Runner etc. that do not require premium gas. But you knew going in that a Lexus (like any other luxury vehicle) requires premium gas, and still bought it!!!

Why do you think all luxury car makers require premium gas for their vehicles, while it is not required for conventional cars? Do you think BMW, Mercedes Benz, Porsche, Audi, Lexus, Acura, etc. are all blowing smoke up our a**???

jskennedy

apologies for my rambling responses not being as constructive as yours

just replying to all the lovely questions & comments

purpose of original post was a sharing of knowledge, nothing more/less, face value

need no validation for my actions

although the data may validate those who are using premium & 2nd guessing their choice


jeep's quality/reliability dropped earlier this decade & disappointed me, doubt i buy another

bought the lexus for the quality, economy & technology, how can you not love that mouse control

correct, you're very observant

pilots & 4runners don't do much for me

i did strongly consider acadias & highlanders

octane rating was not a concern

i'm not sure, but i'm betting you have a fine answer

no