What fuel grade are you using in your RX350?
08-05-21, 12:08 PM
#331
I'll begin with the statement that I firmly believe that buying and owning a car entitles you to own it however you want to without judgement from onlookers. Paint it pink, drop it to 1" off the ground and run it on used fryer oil if you want. You bought it, own it like you want.
The engineers who design engines do so by making certain assumptions, and placing certain expectations on how it's used. "If you want the thing I built to do X, then you need to do Y and Z to make it happen." In all cases, those conditions are chosen for good reasons by people who are experts.
Clearly modern engines survive and perform just fine using less than recommended octane. But that's not what the designers recommend when they designed the engine. And since I'm not a mechanical or fluids expert, I'm OK taking their word on their recommendations. If you want the engine to perform as designed, then use the recommended fuel. I'm not saying bad things happen if people don't, or that they'd even notice a difference. But I already have a solid answer from the designers if you do. Lots of people will say I'm wasting money but in truth I waste more money on things far less important than the second most expensive thing I own. I just consider the fuel type when I'm evaluating overall cost to own when making a buying decision.
But, to each their own.
The engineers who design engines do so by making certain assumptions, and placing certain expectations on how it's used. "If you want the thing I built to do X, then you need to do Y and Z to make it happen." In all cases, those conditions are chosen for good reasons by people who are experts.
Clearly modern engines survive and perform just fine using less than recommended octane. But that's not what the designers recommend when they designed the engine. And since I'm not a mechanical or fluids expert, I'm OK taking their word on their recommendations. If you want the engine to perform as designed, then use the recommended fuel. I'm not saying bad things happen if people don't, or that they'd even notice a difference. But I already have a solid answer from the designers if you do. Lots of people will say I'm wasting money but in truth I waste more money on things far less important than the second most expensive thing I own. I just consider the fuel type when I'm evaluating overall cost to own when making a buying decision.
But, to each their own.
08-05-21, 01:33 PM
#332
Intermediate
I'll begin with the statement that I firmly believe that buying and owning a car entitles you to own it however you want to without judgement from onlookers. Paint it pink, drop it to 1" off the ground and run it on used fryer oil if you want. You bought it, own it like you want.
The engineers who design engines do so by making certain assumptions, and placing certain expectations on how it's used. "If you want the thing I built to do X, then you need to do Y and Z to make it happen." In all cases, those conditions are chosen for good reasons by people who are experts.
Clearly modern engines survive and perform just fine using less than recommended octane. But that's not what the designers recommend when they designed the engine. And since I'm not a mechanical or fluids expert, I'm OK taking their word on their recommendations. If you want the engine to perform as designed, then use the recommended fuel. I'm not saying bad things happen if people don't, or that they'd even notice a difference. But I already have a solid answer from the designers if you do. Lots of people will say I'm wasting money but in truth I waste more money on things far less important than the second most expensive thing I own. I just consider the fuel type when I'm evaluating overall cost to own when making a buying decision.
But, to each their own.
The engineers who design engines do so by making certain assumptions, and placing certain expectations on how it's used. "If you want the thing I built to do X, then you need to do Y and Z to make it happen." In all cases, those conditions are chosen for good reasons by people who are experts.
Clearly modern engines survive and perform just fine using less than recommended octane. But that's not what the designers recommend when they designed the engine. And since I'm not a mechanical or fluids expert, I'm OK taking their word on their recommendations. If you want the engine to perform as designed, then use the recommended fuel. I'm not saying bad things happen if people don't, or that they'd even notice a difference. But I already have a solid answer from the designers if you do. Lots of people will say I'm wasting money but in truth I waste more money on things far less important than the second most expensive thing I own. I just consider the fuel type when I'm evaluating overall cost to own when making a buying decision.
But, to each their own.
As a sidelight and as a new RX350 owner (2021), I was surprised not to see near the refill port the recommended-octane label so commonly found in other vehicles, including my LC500.
Last edited by redhot47fl; 08-05-21 at 04:23 PM.
08-05-21, 04:34 PM
#334
I agree with you, but the...discussion...here seems to be about the wisdom/efficacy of using higher-than-recommended-octane fuel, not lower than recommended. The RX Owner's Manual (page 444) calls for "87 octane (Research Octane Number 91) or higher," which presumably is the engineers' recommendation. So, I'm guessing that you’re perfectly fine - as am I - with using regular 87 octane, but nothing lower (not that anything lower can be found in most places).
As a sidelight and as a new RX350 owner (2021), I was surprised not to see near the refill port the recommended-octane label so commonly found in other vehicles, including my LC500.
As a sidelight and as a new RX350 owner (2021), I was surprised not to see near the refill port the recommended-octane label so commonly found in other vehicles, including my LC500.
I should have mentioned I'm coming at it from what my 2016 manual says, "Select 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 (Research Octane Number 91)."Everything I've read about using higher than recommended says there is no point in doing so.
08-05-21, 04:35 PM
#335
I agree with you, but the...discussion...here seems to be about the wisdom/efficacy of using higher-than-recommended-octane fuel, not lower than recommended. The RX Owner's Manual (page 444) calls for "87 octane (Research Octane Number 91) or higher," which presumably is the engineers' recommendation. So, I'm guessing that you’re perfectly fine - as am I - with using regular 87 octane, but nothing lower (not that anything lower can be found in most places).
As a sidelight and as a new RX350 owner (2021), I was surprised not to see near the refill port the recommended-octane label so commonly found in other vehicles, including my LC500.
As a sidelight and as a new RX350 owner (2021), I was surprised not to see near the refill port the recommended-octane label so commonly found in other vehicles, including my LC500.
A Lexus rep in Canada told me a few years ago that all testing was done on 91 octane, so going above that would be wasteful IMO. I have no written proof of this, but I believed him.
08-06-21, 12:06 AM
#337
Which raises the question -- what is the 2GR FKS compression ratio, actually? With VVT-iW on the intake cam, isn't it a range, rather than a single figure? Isn't the official printed specification actually the maximum ratio, i.e. the Otto cycle ratio?
https://en.wikipedia.org/wiki/VVT-i
https://en.wikipedia.org/wiki/VVT-i
Last edited by dibl; 08-06-21 at 01:11 AM.
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mrolds69 (08-07-21)
08-06-21, 07:22 AM
#338
I understand that the first couple of RX generations were premium-only gas, and it was considered to be a drag on sales. When Gen 3 came out, the sales guys were all thrilled to tout the "regular gas" feature, as I heard when looking at the 2014s and 2015s. So I believe it's all marketing driven, including the "minimum required octane" lingo in the manual.
08-06-21, 08:27 AM
#339
Driver School Candidate
Which raises the question -- what is the 2GR FKS compression ratio, actually? With VVT-iW on the intake cam, isn't it a range, rather than a single figure? Isn't the official printed specification actually the maximum ratio, i.e. the Otto cycle ratio?
https://en.wikipedia.org/wiki/VVT-i
https://en.wikipedia.org/wiki/VVT-i
Toyota 2GR-FE/FSE/FKS 3.5 V6 Engine Specs, Problems, Reliability, oil, Camry, Highlander, Lexus GS/IS/ES 350 (motorreviewer.com)
08-06-21, 08:36 AM
#340
08-06-21, 08:38 AM
#341
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Cocal (08-06-21)
08-07-21, 02:00 PM
#342
When you started talking about compression, it got me thinking. I totally understand how higher compression engines need better fuel. The truth is, I don't really know a lot about the computer controlled engines, other than I know they compensate for changes. You can't really compare a 2000 engine to a 2021 engine. Even if you say "a few years ago a Lexus rep said...", that was a few years ago. You can't really compare the performance of a 2020 MDX to a 350 RX, the MDX has 9 speeds, and I think it's a lot less weight, and it's a different engine. I know the RX H engine is like over a 13+ compression ratio (Atkinson?)and you need premium fuel. That's what I read someplace before I bought my car. I was looking at the hybrid RX and trying to figure out why it needs premium fuel. That's because of the "cycle* which I don't really understand.
I do understand a bit about the "tuners" and how they tweak things. I'm a new member, I'm not a troll, it's all interesting! Here's some food for thought. I know Lexus has a sophisticated computer set up. They can tell if you brake or corner hard, your speed, and a gazillion other things. Suppose your engine blows up at 12K miles. They tow the car to the dealer, the dealer plugs in your port, they scan it. They say...hey,,,the timing shows as advanced, it looks like the air/fuel ratio is tweaked, all the parameters for fuel are whack, we think you ran high test gas and that's why the engine blew.They test your fuel and say it's the wrong fuel for the car. We are not paying for a new engine. Could that happen? Who knows?
I do understand a bit about the "tuners" and how they tweak things. I'm a new member, I'm not a troll, it's all interesting! Here's some food for thought. I know Lexus has a sophisticated computer set up. They can tell if you brake or corner hard, your speed, and a gazillion other things. Suppose your engine blows up at 12K miles. They tow the car to the dealer, the dealer plugs in your port, they scan it. They say...hey,,,the timing shows as advanced, it looks like the air/fuel ratio is tweaked, all the parameters for fuel are whack, we think you ran high test gas and that's why the engine blew.They test your fuel and say it's the wrong fuel for the car. We are not paying for a new engine. Could that happen? Who knows?
08-07-21, 02:12 PM
#343
[QUOTE=. Suppose your engine blows up at 12K miles. They tow the car to the dealer, the dealer plugs in your port, they scan it. They say...hey,,,the timing shows as advanced, it looks like the air/fuel ratio is tweaked, all the parameters for fuel are whack, we think you ran high test gas and that's why the engine blew.They test your fuel and say it's the wrong fuel for the car. We are not paying for a new engine. Could that happen? Who knows?[/QUOTE]
This could never happen as the warning is only not to go below 87 octane there is no limit how high in octane you go, but if you were to use aviation fuel or something similar than of course you'd be on your own.
This could never happen as the warning is only not to go below 87 octane there is no limit how high in octane you go, but if you were to use aviation fuel or something similar than of course you'd be on your own.
08-07-21, 02:24 PM
#344
Instructor
I'll always remember our salesperson's remark when we bought our 2011 RX350. "It runs on regular, it runs better on premium." Sage advice without all the technical stuff.
Ray A.
Ray A.
08-08-21, 08:48 AM
#345
Intermediate
I think a much more accurate quote: "it runs on regular, it might be slightly more efficient on premium."
US Energy Information Administration: Gasoline Explained
"Modern engine computers minimize this condition [pre-ignition, when the fuel ignites on its own before the spark ignites it, i.e., knocking] by controlling the timing of valves and fuel injection; however, this control mechanism can also come with a fuel-efficiency or emissions penalty."
US Energy Information Administration: Gasoline Explained
"Modern engine computers minimize this condition [pre-ignition, when the fuel ignites on its own before the spark ignites it, i.e., knocking] by controlling the timing of valves and fuel injection; however, this control mechanism can also come with a fuel-efficiency or emissions penalty."