What fuel grade is everyone using on their 2012-2015 RX?
01-28-16 | 09:53 AM
#256
Driver School Candidate
Joined: Feb 2015
Posts: 36
Likes: 0
From: FL
From what I've read, lower octane ignites (from the spark not the heat) sort of wildly and irregularly, thus the pinging, vibrations or whatever. Higher octane burns slower, evenly or regularly, so no/less pinging, and also makes the engine run smoother and cooler. This steadier burn may give better mpg and also running smoother may have better performance. I use 89 oct without ethanol in my 15 F-Sport. I believe these, as many other newer vehicles, have enough computer sense to control the spark and/or controls the timing so they can run on about anything. I've tried 87, 89, 91 and 93 in mine and have chosen 89. I've felt vibes, pinging or hesitation (don't quite know how to call it) with 87 but not with any of the other octanes.
01-29-16 | 07:00 AM
#258
Driver
Joined: Jan 2013
Posts: 121
Likes: 0
From: TX
To what I know
Regular 87 will burn at lower heat, lower compression.
Premium 93 will burn at Higher heat, Higher Compression.
Every new car nowadays, not just RX, Their ECU is made to sense and Retard the timing, or go full advance. The best fuel will be the Fuel which is recommended by the Factory, because that is based on the engineered engine compression.
Let say if you put in Premium for an engine that required Regular, the Timing have to be retarded, Fuel will be wasted more, and the engine lose it efficiency in order to protect itself, from where it was engineered to do.
Vice Versa, if you were to put Regular into an engine that was engineered for Premium, the Computer will have to Advance the timing, and spark fire up earlier, but this will not be enough, and your engine will more likely burn a hole into Itself at higher RPM, and under load.
For all that said in Theory, I do not believe burning Premium in the RX will make it stronger, faster, or more efficient. The most Efficient was engineered, scaled, tested, proved carefully before they print out the Manual for you. :-)
Regular 87 will burn at lower heat, lower compression.
Premium 93 will burn at Higher heat, Higher Compression.
Every new car nowadays, not just RX, Their ECU is made to sense and Retard the timing, or go full advance. The best fuel will be the Fuel which is recommended by the Factory, because that is based on the engineered engine compression.
Let say if you put in Premium for an engine that required Regular, the Timing have to be retarded, Fuel will be wasted more, and the engine lose it efficiency in order to protect itself, from where it was engineered to do.
Vice Versa, if you were to put Regular into an engine that was engineered for Premium, the Computer will have to Advance the timing, and spark fire up earlier, but this will not be enough, and your engine will more likely burn a hole into Itself at higher RPM, and under load.
For all that said in Theory, I do not believe burning Premium in the RX will make it stronger, faster, or more efficient. The most Efficient was engineered, scaled, tested, proved carefully before they print out the Manual for you. :-)
Second, science is exactly opposite of what you mentioned. Octane rating indicates how much fuel can be compressed before it ignites. Lower rating means it can handle lower compression. Minimum octane rating for engine is determined by your engine's compression ratio before it leads to knocking. So in RX an 87 rating fuel is minimum required based on the engine's compression ratio. Lower than that you will get knocking and bad mpg. So a 93 rating fuel will not lead to bad mpg but you will get better performance (not noticeable in RX) due to higher octane rating.
Timing is retarded only if you get knocking to get rid of it. Your statement is exact opposite of what happens.
04-27-17 | 08:40 AM
#259
Driver School Candidate
Joined: Apr 2017
Posts: 2
Likes: 0
From: District Of Columbia
What gas to use for better performance Lexus 2014 RX350
In my Lexus 2014 RX 350 manual it mentions the Fuel to use is
87 (Research octane number 91) or higher
If I am looking for better performance, should I try 89 or 91 octane? Will that hurt my engine?
87 (Research octane number 91) or higher
If I am looking for better performance, should I try 89 or 91 octane? Will that hurt my engine?
04-27-17 | 09:27 AM
#262
Welcome to Club Lexus!
Dozens of threads on this topic, try the search feature! Here are a couple to get you started
https://www.clublexus.com/forums/rx-3rd-gen-2010-2015/838940-switching-from-premium-to-regular-gas.html
https://www.clublexus.com/forums/rx-3rd-gen-2010-2015/686969-anyone-using-premium-fuel-in-the-2013-rx-350-a.html
https://www.clublexus.com/forums/rx-...s-regular.html
Dozens of threads on this topic, try the search feature! Here are a couple to get you started
https://www.clublexus.com/forums/rx-3rd-gen-2010-2015/838940-switching-from-premium-to-regular-gas.html
https://www.clublexus.com/forums/rx-3rd-gen-2010-2015/686969-anyone-using-premium-fuel-in-the-2013-rx-350-a.html
https://www.clublexus.com/forums/rx-...s-regular.html
04-27-17 | 09:36 AM
#263
Lexus Champion
Joined: Aug 2007
Posts: 4,507
Likes: 35
From: Bethlehem Twsp. Pennsylvania
09-26-17 | 05:19 PM
#264
Driver
Joined: Jul 2014
Posts: 108
Likes: 3
From: FL
2015 RX350 Octane question
Let me ask..
Regarding gas octane.. I know the car is rated for standard 87, but I came from years and years of owning BMW and always HAD to use 93. So, admittedly there has been several times where I still use the 93, and have not noticed any bad effects. Can I just drop this back to 87, or because I have been using 93 in the lexus RX350 I should stick with that? Also, is heat a consideration? As I understand it.. 87 will ignite at a lower temp, and the 93 will take a higher temp? I live in Miami, and right now its about 98F.. so, is it best to use the higher octane in this heat?
What I have done so far.. is use the higher octane when the weather is super hot.. and the lower octane when the weather is a bit cooler.. is that a good logic to use?
Regarding gas octane.. I know the car is rated for standard 87, but I came from years and years of owning BMW and always HAD to use 93. So, admittedly there has been several times where I still use the 93, and have not noticed any bad effects. Can I just drop this back to 87, or because I have been using 93 in the lexus RX350 I should stick with that? Also, is heat a consideration? As I understand it.. 87 will ignite at a lower temp, and the 93 will take a higher temp? I live in Miami, and right now its about 98F.. so, is it best to use the higher octane in this heat?
What I have done so far.. is use the higher octane when the weather is super hot.. and the lower octane when the weather is a bit cooler.. is that a good logic to use?
09-26-17 | 06:30 PM
#265
Lead Lap
Joined: Nov 2013
Posts: 3,669
Likes: 904
From: IL
Many threads on this topic. The answer is no, using Premium is a car that is not tuned for it is just a waste of your money.
High Octane fuel resists pre-combustion "ping" in high compression engines. If it is not going to ping, don't bother with the fuel.
On a historic note, Hi-Test fuels once were a source of fuel system cleaners and additives that regular grade fuel didn't have.
Carbureted and low energy ignition engines would require more frequent cleanings and an occasional tank of "Ethyl" would
provide a bit of detergent. Now that all grades of fuel have similar additives the difference is pretty much limited to Octane ratings.
High Octane fuel resists pre-combustion "ping" in high compression engines. If it is not going to ping, don't bother with the fuel.
On a historic note, Hi-Test fuels once were a source of fuel system cleaners and additives that regular grade fuel didn't have.
Carbureted and low energy ignition engines would require more frequent cleanings and an occasional tank of "Ethyl" would
provide a bit of detergent. Now that all grades of fuel have similar additives the difference is pretty much limited to Octane ratings.
09-27-17 | 06:57 PM
#268
Driver
Joined: Jul 2014
Posts: 108
Likes: 3
From: FL
