Last Sat before getting on the interstates for our 1 hour trip I saw the tank is almost empty, stopped at the gas station and they only have 87 and 89. I filled up the tank with 89 and for 50 miles on the interstate cruising between 70-79, I average 26.1 mpg. The car has 16,xxx miles so it is not that bad. I may just use 89 from now on.

 

That's what I was referring to but I wasn't very clear. I was agreeing when the 2012 RX350 goes to regular fuel there shouldn't be any concerns about carbon and cat problems. Toyota has been using this engine for several years in a lot of applications on regular fuel.

 

I've put nothing but 87 in my 2010 RX350 and I get 25 mpg on the highway and 20-21 overall and I'm happy with that.

I disagree with this. The difference in the gas is the octane rating. Octane has nothing to do with carbon emissions and will have no effect on the catalytic converter.

 

There is no "re-tune" ALL Lexus engines run on regular 87. Its wasn't posh to advertise lowly poor man fuel! No with the mess this country finds itself, if Lexus wants to sell cars in the next 18 months they HAD to come clean.

I have a 2010 RX450 and it had 11,700 mi. Never put anything but 87. It runs perfect, never had it in for any issue, except for the oil change.

"a fool and his money are soon parted."

 

x2 with "The X Men". de/re-tuned to operate safely on 87 for 2012 but those with 2010-11 should continue using 91+. Yes and yes, that some have used 87 for many years without any issues. Only manufactures that has the "switch" systems I know are Honda and Hyundai. On selective models it actually has system to automatically lower the timing value to run safely on 87 but automatically bumps the value when higher octane is found to increase performance. Without the “switch” system a typical knock-sensor and ECM will have “workout” trying to prevent damage to the engine. Lexus owner’s manual has warning to only use 87 when 91+ is not available but fill-up with 91+ as soon as it is available. There is absolute no benefit of using premium fuel that was designed to operation on 87 but should use 91+ if it was built/designed. No Toyota/Lexus that I know has the “switch” system and there are many articles explaining about the importance of using manufacture recommended octane. For average users like me with 12k/yr will be adding about $200/yr to fuel cost if I achieved exact same MPG using 87, but with my testing/usage I will closely break-even with improved performance using 91+.

 

You said it..... "recommandation" not REQUIRED. (use spell check next time) recommended means its all good. 87, 89, 92, 93 etc.

I stand by my comment.
by the way my 1st. cousin owns TWO dealerships on the east coast. He gets a chuckle out of all the so called false facts.

 

I am absolutely no expert on this subject and I currently run 91 in our 2011 RX. However, we ran 87 in our 2001 for eight of the eleven years we had it without a problem. I don't know what the "switch" system is that Sightdev talks about in post #26 but in know that the 2001 had VVT (variable valve timing) and I feel relatively certain that the 2011 has the same type of system. Based on my limited knowledge, that should take care of the issue of using 87 vs 91.

 

When regular was ok'd for the 2011 ES the word used was "re-rated" for regular (whatever that means). In the case of the ES the whole regular vs. premium recommended vs. required has been murky from the time the current gen was introduced as a 2007 model. While researching the 2007 ES I read a Q&A with someone from Toyota/Lexus and he said premium fuel was required to acheive the advertised hosepower, which was 272 vs. the 268-270 found in other Toyota models using the same engine.

IMO you can't go wrong with either grade of fuel and Lexus is finally clearing the whole issue up by going to regular fuel for both the ES and RX. Whether its re-tuning, re-rating or whatever it's about time.

 

X men, you may be correct regarding the 2001 on regular vs premium. I no longer have th owner's manual or I would check it. I kept the sales brochure, but I can find nothing in there.

 

All the Lexus we had/have LS400, LS430, SC400, SC430, RX330, and now RX350 all had/have sticker on the gas door that noted "PREMIUM ONLY". Selective Honda/Hyundai/Mazda models that I know have "PREMIUM RECOMMENDED". Note, Lexus is "PREMIUM ONLY" but owner can use what works for them regardless what Lexus notes on the gas door and on owners manual.

 

I've been using premium 93 for all of my cars. Last two weeks, switch to 87 for the Toyota to see how it goes. I felt it's burning more gaz and the acceleration gets slower. Hmmm, may be because " cheaper has a price" feeling. However, I'll only use 93 for my Rx350 just make me feel better hahahah

 

Does using premium on a 2012 increase the horsepower back to 270 and or increase the gas mileage?

 

No and No.
it will only increase your fuel cost for that month.

 

I guess the question is did they actually make changes to the engine in 2012 or did they just tell owners to use regular like owners of previous years RX's were doing anyway without performance issues?

 

...well I believe that probably what they did is "detuned" the engine engineering wise (I hear is not a big deal) thus loosing a couple of horses.....my gas station owner swears that the higher octane gives on the average a "couple" of more miles per gallon...but then he owns the gas station, if you know what I mean...lol....
I traded in an Acura MDX 2011....the gas mileage was lousy (14mpg local) and Acura emphasizes the use of premium...some people "foughht" the recommendation from Acura and put regular...not me I bought the sucker and down the road you will see damage on the engine....
As far as the Rx that I have now I am very happy, better mileage,18 mpg local and regular gas, 50 cents less per gallon,,,,happy person here