What fuel grade are you using in your RX350?
11-14-21, 02:35 PM
#376
I have yet to see any independent, controlled test that indicates any significant difference in fuel economy when switching from 87 to 93 octane. In fact, AAA ran an extensive test here: Premium Fuel Study (aaa.com) that showed switching to higher octane gas was simply a waste of money.
Further, oil companies and gasoline retailers scrupulously avoid suggesting using higher octane gas will result in better fuel economy. Does anyone believe they would do that if they could prove otherwise?
But, it's your money.
Further, oil companies and gasoline retailers scrupulously avoid suggesting using higher octane gas will result in better fuel economy. Does anyone believe they would do that if they could prove otherwise?
But, it's your money.
11-14-21, 03:00 PM
#377
I think it's a common misconception among many folks that Octane is some kind of "performance additive". Octane is simply the thing that keeps the gas/air mixture from igniting under pressure instead of with the spark. Higher octane fuel can be compressed to higher pressures without pre-mature ignition. It's only needed if your engine compression creates enough pressure prior to ignition to make this an issue. It's completely useless to run a car on higher octane than what is recommended because if the engine compression doesn't reach pressure levels that need higher octane then it's useless. I'm not even sure why it would need to be studied. It's only meaningful the other direction, where you run a car on lower octane than recommended, because you invite knocking. And even then, modern engines can account of this and the informal studies I've seen are basically "your results will vary" if running lower changes hp or mpg in a way you can isolate or notice.
11-14-21, 05:51 PM
#378
1. Atkinson Cycle Engine
2. VVT-iW
3. 2GR-FKS
If you want to understand how your Gen. 4 RX 350 handles 87 octane fuel, you need to fully understand these three designs. Together, they explain how your RX is able to accelerate uphill with no spark knock on 87 octane. I am not criticizing the engine design -- it's actually pretty ingenious. I'm just showing how they lowered the compression ratio to avoid the knocking.
BTW, there's no way they used 87 octane to obtain the advertised HP and torque of the 2GR-FKS. IMHO.
2. VVT-iW
3. 2GR-FKS
If you want to understand how your Gen. 4 RX 350 handles 87 octane fuel, you need to fully understand these three designs. Together, they explain how your RX is able to accelerate uphill with no spark knock on 87 octane. I am not criticizing the engine design -- it's actually pretty ingenious. I'm just showing how they lowered the compression ratio to avoid the knocking.
BTW, there's no way they used 87 octane to obtain the advertised HP and torque of the 2GR-FKS. IMHO.
Last edited by dibl; 11-14-21 at 05:54 PM.
11-14-21, 09:13 PM
#379
Intermediate
1. Atkinson Cycle Engine
2. VVT-iW
3. 2GR-FKS
If you want to understand how your Gen. 4 RX 350 handles 87 octane fuel, you need to fully understand these three designs. Together, they explain how your RX is able to accelerate uphill with no spark knock on 87 octane. I am not criticizing the engine design -- it's actually pretty ingenious. I'm just showing how they lowered the compression ratio to avoid the knocking.
BTW, there's no way they used 87 octane to obtain the advertised HP and torque of the 2GR-FKS. IMHO.
2. VVT-iW
3. 2GR-FKS
If you want to understand how your Gen. 4 RX 350 handles 87 octane fuel, you need to fully understand these three designs. Together, they explain how your RX is able to accelerate uphill with no spark knock on 87 octane. I am not criticizing the engine design -- it's actually pretty ingenious. I'm just showing how they lowered the compression ratio to avoid the knocking.
BTW, there's no way they used 87 octane to obtain the advertised HP and torque of the 2GR-FKS. IMHO.
11-15-21, 03:55 AM
#380
That's hard to say -- as others have diligently tried to measure the difference, it seems to be quite small. In my little experiment, it came out slightly over 1 mpg. more with higher octane fuel, compared to 87.
11-15-21, 05:24 AM
#381
If we assume Wikipedia is accurate, we now have the answer. Strangely, and humorously - given all the words devoted to octane discussions - Lexus uses NEITHER regular nor premium! They use that odd pump "splash blend" mid-grade! Ok, ok, I guess 91 qualifies as premium in some places, but if a pump has 87, 91 and 93, 91 it is mid-grade in my book.
11-15-21, 07:06 AM
#382
Cars operating at lower than required octane do lose HP and can lose MPG as a result. However the HP loss would be so small a driver would never really feel it. The MPG loss (or gain...) might also be so small that it would be very difficult to isolate it from all the other variables that can alter mpg in real-world driving.
But I suspect they would put their best foot forward. Or maybe use both and take the best result (I would not put it past them). But understanding what the engine is doing to compensate for lower octane should definitely point to a small HP loss. The harder issue is that the car is using less fuel too (if the car is backing down on the fuel/air mixture or adjusting via Atkinson cycle). This might be the reason why MPG results vary - this might raise or lower MPG based on how and where you drive.
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dibl (11-16-21)
11-15-21, 07:35 AM
#383
1. Atkinson Cycle Engine
2. VVT-iW
3. 2GR-FKS
If you want to understand how your Gen. 4 RX 350 handles 87 octane fuel, you need to fully understand these three designs. Together, they explain how your RX is able to accelerate uphill with no spark knock on 87 octane. I am not criticizing the engine design -- it's actually pretty ingenious. I'm just showing how they lowered the compression ratio to avoid the knocking.
BTW, there's no way they used 87 octane to obtain the advertised HP and torque of the 2GR-FKS. IMHO.
2. VVT-iW
3. 2GR-FKS
If you want to understand how your Gen. 4 RX 350 handles 87 octane fuel, you need to fully understand these three designs. Together, they explain how your RX is able to accelerate uphill with no spark knock on 87 octane. I am not criticizing the engine design -- it's actually pretty ingenious. I'm just showing how they lowered the compression ratio to avoid the knocking.
BTW, there's no way they used 87 octane to obtain the advertised HP and torque of the 2GR-FKS. IMHO.
I've had it from a person at Lexus Canada that all tests were done with 91 octane.
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dibl (11-15-21)
11-15-21, 10:26 AM
#384
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bamalam (11-15-21)
11-22-21, 05:24 AM
#385
Driver School Candidate
Midgrade
I too use midgrade per the owners manual. Upon purchase that’s all I have used. However, I have noticed a bit acceleration hesitation so I don’t know if it’s related.
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DesertFox6 (02-25-22),
Lexspeed (02-25-22)
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GlenK (02-27-22)
02-25-22, 02:34 PM
#388
It's Alive....the thread that will never die on every auto Forum in the US.
I refer you back to post #296 for the only answer that makes sense.
I refer you back to post #296 for the only answer that makes sense.
02-25-22, 09:14 PM
#389
it's been 3 months.
