When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My wife also likes to use premium. I think 99% of these instances are nothing more than the placebo effect. Just like how the car just runs "better" after a car wash.
My only disagreement with your comment is in my opinion it would be 100%. There is no evidence that the octane rating of the gas would have anything to do with the performance of the engine. At least none that is detectable by the driver. Maybe on a dyno. And then, just maybe.
I find this quote interesting from the FTC: “In most cases, using a higher-octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage or run cleaner.”
Had a 2011 for 2 years and now a 2015 for 4 years. I have used nothing but 87 octane Regular and both RX350 run great with no ping and no problems. I limit my 93 octane purchases to just my 450 Hp 911 with TT 3.0 L.
I got delivery of a 2010 Lexus RX-350 yesterday and loving it so far.
I've done some reading on the fuel octane to use and from what I have read 87 octane is fine to use. But when I opened the fuel cap is says "PREMIUM UNLEADED FUEL ONLY". Should I use 91 Octane or 87?
I got delivery of a 2010 Lexus RX-350 yesterday and loving it so far.
I've done some reading on the fuel octane to use and from what I have read 87 octane is fine to use. But when I opened the fuel cap is says "PREMIUM UNLEADED FUEL ONLY". Should I use 91 Octane or 87?
For the best engine performance; use 91 octane. However, I believe that 3.5 V6 will still run fine on 87 octane. I only use 93 octane in my 2015 RX350 and it runs like a dream and idles smooth as silk.
For the best engine performance; use 91 octane. However, I believe that 3.5 V6 will still run fine on 87 octane. I only use 93 octane in my 2015 RX350 and it runs like a dream and idles smooth as silk.
If you say so. I will just use 93 octane in my ride. I always just put 93 octane in any engine with over 10:1 compression. I only use 87 octane in engines with less than 10:1 compression. The Lexus(Toyota) 3.5 has a 10:8 compression engine.
The owners manual for my wife's 2015 RX350 FWD specifies regular 87 octane so that is what she runs in it. She has reported no issues with engine / drivetrain performance during more than four years of ownership. Works for me.
For what it's worth, we have been using 89 octane (10% ethanol blend) for my wife's RX400h for the past 4 years and I have also been using this same blend for my LS460L. There have been no problems whatsoever. Here In IA, 10% ethanol is 13 cents cheaper than 87 octane (regular) and 30 cents cheaper than premium. I have tried premium (91 to 93 octane) once in a while for testing purposes and I have not seen any real difference in fuel efficiency or performance. Unless we are absolutely told that we have to use premium for the new RX450h, we will continue to use the 89 octane ethanol blend.
For what it's worth, the 2010-2012 only "requires" 91 octane to the extent that you want to get the rated 275 horsepower. The drop to 87 octane in 2012 is related to the drop in rated horsepower to 270. Lower octane means changes in limits of engine timing meaning less power. See the Toyota Highlander with the same engine - rated at 270hp on 87 octane in 2010.
Lexus marketing just thought their luxury vehicle should carry a higher hp rating than a pedestrian Toyota. Unless you're drag racing, towing, or have another requirement for the extra few hp, there's really no need. The last 200,000 miles on my 235,000 mile 2010 have been on 87 octane - no issues, and confirmed OK with Lexus service.
As the owner's manual says
Premium unleaded gasoline with an octane rating of 91 (Research Octane Number 96) or higher required for optimum engine performance. If 91 octane cannot be obtained, you may use unleaded gasoline with an octane rating as low as 87
This was changed in 2012, along with the hp reduction, to
Select octane rating 87 (Research Octane Number 91) or higher
Weird because these are from the 2011 RX350's owner manual, not to mention the premium unleaded fuel sticker by the gas cap. I'm sure you got your money's worth from using 87 instead of 91 though.
WOW. The octane debate has been ongoing for decades on every forum that I have been a member of regardless of make or model. Most newer engines(GDI mainly) has a statement in the owners manual including the 2015 Lexus RX350 that states the engine requires 87 or higher octane. Not 87 octane only. The "or higher" clause means that the engine will run at the bare minimum performance with 87 octane and run better with high octane. For some reason people seem to miss that point and think the engine only is designed to run 87 octane.
It is like saying that a product like a table needs at the minimum four screws to be stable and bear a certain weight, but using more than four screws would make it more stable and increase it load bearing ability with the additional number of screws used beyond four. Do that mean that the table is only design for four screws? No, it means that the table will work at it minimum ability with four screws. However, it will perform at a high potential in relation to number of screws used over the bare minimum four needed.
The same for the Lexus RX350 engine. It will run fine and at its minimum acceptable performance level with 87 octane, but the engine should run better as the octane increases.
Last edited by carguy75; Mar 14, 2023 at 07:38 AM.
This thread is directed toward the 2010 and 2011 models, not 2015. Yes, the drivetrain is the same for the 2010-2015 RX350s, but the requirements in the owner's manual for the earlier models are different.
If the instructions to assemble a table require a minimum of 4 screws and you only have 3, then you're SOL. Yes, you can still make 3 screws work, but is it the same as 4 screws? No.
At the end of the day, the 3rd gen RX350 still receives lots of praise for its reliability and I doubt the target audience for original owner RX350s cared enough to look at the manual.
This thread is directed toward the 2010 and 2011 models, not 2015. Yes, the drivetrain is the same for the 2010-2015 RX350s, but the requirements in the owner's manual for the earlier models are different.
If the instructions to assemble a table require a minimum of 4 screws and you only have 3, then you're SOL. Yes, you can still make 3 screws work, but is it the same as 4 screws? No.
At the end of the day, the 3rd gen RX350 still receives lots of praise for its reliability and I doubt the target audience for original owner RX350s cared enough to look at the manual.
In regards to the 2010-2011 models, then yes you are correct. Using less than 91 octane could possibility do more harm over the long term of the engine's life than just using what is recommended ;which is 91 octane or higher octane. Engine knock is not good for the health of an engine regardless of how many owners state that using 87 in their engine is fine long term. I had an 2011 RX350 AWD and only used 93 octane and the engine always ran perfectly as designed. However, I am sure that many owners will state they used 87 octane in their 2010 and 2011 models and the engine still runs perfectly fine; if not even better than with 91 octane.
Hence why these octane debates never really ends with a true winner on either side of the debate.
Last edited by carguy75; Mar 15, 2023 at 06:45 AM.
