Octane for RX350h?
Intermediate
Joined: Feb 2022
Posts: 286
Likes: 147
From: AR
For those of you who live in a state with Kroger grocery stores, you can earn some nice discounts on their gas by shopping there. I usually get between 70 cents to a dollar a gallon off every fill-up. That makes it a lot easier to use premium. Kroger usually buys their top-tier gas from Shell. They use annual contracts, and I've never seen Ethanol included.
Pole Position
Joined: Oct 2002
Posts: 3,067
Likes: 457
From: Pennsylvania
For those of you who live in a state with Kroger grocery stores, you can earn some nice discounts on their gas by shopping there. I usually get between 70 cents to a dollar a gallon off every fill-up. That makes it a lot easier to use premium. Kroger usually buys their top-tier gas from Shell. They use annual contracts, and I've never seen Ethanol included.
Instructor
Joined: Jan 2023
Posts: 1,243
Likes: 545
From: British Columbia
Intermediate
Joined: Mar 2011
Posts: 261
Likes: 182
From: TX
I found this:
"A by-product of this is that Atkinson cycle engines actually run best on lower-octane fuels. The slower flame propagation of high-octane fuel is detrimental to such an engine, and Prius owners who have made the mistake of running premium fuel in their cars have been rewarded with misfires, check engine and hybrid system warning indicators"
I also found comments stating that the Atkinson cycle, with fast propagation fuel (lower octane) are ideal for hybrids because the engine restarts faster, making for smoother transitions between gas and electric.
YMMV
"A by-product of this is that Atkinson cycle engines actually run best on lower-octane fuels. The slower flame propagation of high-octane fuel is detrimental to such an engine, and Prius owners who have made the mistake of running premium fuel in their cars have been rewarded with misfires, check engine and hybrid system warning indicators"
I also found comments stating that the Atkinson cycle, with fast propagation fuel (lower octane) are ideal for hybrids because the engine restarts faster, making for smoother transitions between gas and electric.
YMMV
Intermediate
Joined: Feb 2022
Posts: 286
Likes: 147
From: AR
I found this:
"A by-product of this is that Atkinson cycle engines actually run best on lower-octane fuels. The slower flame propagation of high-octane fuel is detrimental to such an engine, and Prius owners who have made the mistake of running premium fuel in their cars have been rewarded with misfires, check engine and hybrid system warning indicators"
I also found comments stating that the Atkinson cycle, with fast propagation fuel (lower octane) are ideal for hybrids because the engine restarts faster, making for smoother transitions between gas and electric.
YMMV
"A by-product of this is that Atkinson cycle engines actually run best on lower-octane fuels. The slower flame propagation of high-octane fuel is detrimental to such an engine, and Prius owners who have made the mistake of running premium fuel in their cars have been rewarded with misfires, check engine and hybrid system warning indicators"
I also found comments stating that the Atkinson cycle, with fast propagation fuel (lower octane) are ideal for hybrids because the engine restarts faster, making for smoother transitions between gas and electric.
YMMV
Rookie
Joined: Mar 2023
Posts: 48
Likes: 37
From: MA
Good grief. Thanks to the idiot, we have a whole generation of people who are just CERTAIN that they know better, about everything, than everyone else. The whole world is out to get them I tell you, and they are not going to let it happen!! Tire pressure recommendation from the manufacturer? That's wrong. Suggested octane? It's a scam. Service intervals? Chinese plot. Turbo engines? Russian spies are using them as bugging devices.
Confirmation bias: I'm going to go google articles until I find one that agrees with my paranoia, and bam - I told you it was true, read this!!!
Of course nothing's going to happen to your car if you put less air in the tires or use 87 octane. The reason why you would do these things is what's ridiculous.
The same people that will NOT pay extra for gas, darn it, will instead go out and buy cigarettes, donuts and coffee with it. Yea, that makes MUCH more sense.
Confirmation bias: I'm going to go google articles until I find one that agrees with my paranoia, and bam - I told you it was true, read this!!!
Of course nothing's going to happen to your car if you put less air in the tires or use 87 octane. The reason why you would do these things is what's ridiculous.
The same people that will NOT pay extra for gas, darn it, will instead go out and buy cigarettes, donuts and coffee with it. Yea, that makes MUCH more sense.
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Driver
Joined: May 2023
Posts: 56
Likes: 20
From: CA
I know this is a great debate topic but has anyone actually tried running on 91 versus 87 and noticed any measurable difference in MPG? I plan to run it on 87 if there is only a 1-2 mpg hit on the efficiency. I have 400 miles on the odometer and am still on the original tank the dealer provided which I understand to be 87 based on what I read here. At this time I'm not quite hitting the 37 mpg city mark yet but its a new engine that needs to be broken in I presume. Thanks in advance, this will help me avoid having to do my own experiment.
Last edited by kitlz; May 24, 2023 at 04:08 AM.
Driver
Joined: May 2023
Posts: 56
Likes: 20
From: CA
Thank you @jahnjva and @ggebhardt, exactly what I wanted to hear. its about a 40 cent difference where I live between 87 and 91.
Driver
Joined: Mar 2023
Posts: 65
Likes: 88
From: PA
Have owned my RX350h for about 3,500 miles so far. The first 2,000 or so I used 91-93 octane exclusively. Averaged 35mpg highway and 37mpg city. Switched to 87 and have noticed no difference whatsoever in gas mileage or performance. This is not a performance engine and the Atkinson cycle probably numbs any possible difference in performance if any. No complaints on 87 so I will keep it there and save a few more $$$ than this amazing car does for me already.
Driver
Joined: May 2023
Posts: 56
Likes: 20
From: CA
I'm relatively new to the forum (first Lexus) but are there any Toyota/Lexus techs here who can definitively state that running 87 doesn't do long term harm to the engine? This engine is the same engine (A25A-FXS) as the ES300H and that car states clearly that 87 is the fuel to run. Granted the HP output (~220 vs ~240) is different which means there is at minimum some software differences. If so, my hope is the computer runs a different tune to reduce power and safely/reliably run 87.
Pole Position
Joined: Oct 2002
Posts: 3,067
Likes: 457
From: Pennsylvania
I'm relatively new to the forum (first Lexus) but are there any Toyota/Lexus techs here who can definitively state that running 87 doesn't do long term harm to the engine? This engine is the same engine (A25A-FXS) as the ES300H and that car states clearly that 87 is the fuel to run. Granted the HP output (~220 vs ~240) is different which means there is at minimum some software differences. If so, my hope is the computer runs a different tune to reduce power and safely/reliably run 87.
I doubt that any Lexus tech is going to issue a “definite” proclamation like that. What is definite is page 570 of the manual, that definitely states that the minimum acceptable octane is 87 for the RX350h but is 91
for the RX500h and the non-hybrid RX350 turbo. I’d say it’s pretty definite that if the RX350h would be subject to damage on 87 octane gas, Lexus wouldn’t allow it as they do right here:
