View Poll Results: Which Gas do you use?
Regular
157
49.53%
Plus
51
16.09%
Premium
109
34.38%
Voters: 317. You may not vote on this poll
Poll: Which Gas
08-06-05, 07:34 PM
#46
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Like lots of other people here, I only put regular in my wife's RX300. Not only that, but I now only put regular in my GS400. I notice no difference in performance with the sweet V8, but of course I rarely push it more then 80%. Unless you have forced induction, I say save the cash.
08-19-05, 10:54 AM
#47
Driver School Candidate
Originally Posted by TunedRX300
How does higher octane gas helps tranny hesitation? Gas burns in engines, not in transmissions. Engine is a power plant, tranny is just the transmission line.
The only possible explanation is when tranny shift to a higher gear, RXs that burn premium output lower power than those burn regular so you don't feel as big of a jolt between gears.
Higher octance means higher resistance to explosion. If you put higher octane to engines designed for 87 such as 1MZFE, you get unburned mixtures and lower power. Pay higher price, get lower performance, plus clogging up your catalytic converter with unburned carbon deposit, be careful here.
The only possible explanation is when tranny shift to a higher gear, RXs that burn premium output lower power than those burn regular so you don't feel as big of a jolt between gears.
Higher octance means higher resistance to explosion. If you put higher octane to engines designed for 87 such as 1MZFE, you get unburned mixtures and lower power. Pay higher price, get lower performance, plus clogging up your catalytic converter with unburned carbon deposit, be careful here.
The higher octane 91 ON THE RX ENGINE *can* make it smoother and reduce tranny hesitation. Here's why:
The compression ratio of the RX engine is like 10.4 or something, which is about requireing 91 octane to avoid detonation. However, the car's computer (ECU) can use a trick: retarding the ignition timing and downshifting to reduce detonation (knocking). This technique is effective enough that the RX's ECI can allow 87 octane gas to be used. The drawback is, with retarded timing, you get less power efficiency out of your gas. This is made up for (approximately) by downshifting, but as most 87 octane RX users experience, this means a rougher acceleration as the car double downshifts. (Annoying). In addition, the higher RPM's increase wear on the piston rings and journal bearings. There's always a tradeoff.
If you are 99% light on the acceleration, then 87 is probably better for you. It's economical, and since you don't demand hard acceleration, the car won't need to double downshift that often.
I only recently read about this, so I had been using 87 for the first 1.5 years of RX ownership. I recently switched to 91 (and feeling raped by gas prices) to see the difference. I must not have pulled the right fuse (or not long enough) because it still took awhile for the hesitation to reduce as the ECU adjusted the parameters.
My conclusion:
- 87 is just fine and even better if you are soft on the acceleration
- if you like to push the pedal, then you should move to 91 as that is what the engine was designed for. With 91, it will operate most efficiently (better power for acceleration)
- 91 won't affect MPG much (as I've experienced) unless you are doing a lot of stop and go city driving. Freeway driving will totally overshadow the 91 efficiency increase.
- medium octane, or 89 is the petrol industries joke, sorta. No car manufacturer is designing engines for 89. It's either 87, or 91 (for the USA, that is). If you're knocking at 87, try 89. But in most cases, it's either 87 or 91 that works best.
08-19-05, 11:01 AM
#48
Driver School Candidate
Originally Posted by dialleft
I’m not sure whether the computer timing will increase performance of an engine designed to run on regular. My guess is slight, but I doubt it would be detectible.
So, basically you have been wasting your money on gas higher than 87. I use 87 in our 330 and premium in my 350Z.
So, basically you have been wasting your money on gas higher than 87. I use 87 in our 330 and premium in my 350Z.
On engines (like the RX) which ARE designed for 91 (c/r of 10.4 or something) then yes, 91 will produce more power because the computer does not have to retard timing to reduce detonation; thus getting more optimal power efficiency.
If you can limit yourself to accelerating like Grandma, then 87 is the best economical way to go for an RX owner.
But like the manual says, for optimum performance (acceleration), use 91.
08-19-05, 04:42 PM
#49
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I wish to admit that the folks who said to use premium in my RX330 seem to be correct. I have a 13.5 mile commute, half city, half highway. On 87 octane I averaged 19.4 mpg.. On the last three full tanks I have used 93 octane(no 91 in Ky.) and have averaged 21.6. Also, the very minor hesitation is gone. 
08-19-05, 07:16 PM
#51
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Premium gas.
I just purchased my RX330. I currently pump premium but I find myself only getting 15.5-17.5 miles per gallon. I drive both highways and freeways. I hope my gas mileage will improve. I am used to driving like 45-50 on highways and 80-85mph on the freeway. But even with fast driving shouldn't I be getting more miles per gallon? Will lower gas be better? Help! 
08-21-05, 03:35 PM
#52
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Originally Posted by sriracha
I just purchased my RX330. I currently pump premium but I find myself only getting 15.5-17.5 miles per gallon. I drive both highways and freeways. I hope my gas mileage will improve. I am used to driving like 45-50 on highways and 80-85mph on the freeway. But even with fast driving shouldn't I be getting more miles per gallon? Will lower gas be better? Help!
08-21-05, 04:05 PM
#53
Originally Posted by chimchimm5
I've discussed this on another forum so lemme see if I can clarify something. (I have a 2004 RX330)
The higher octane 91 ON THE RX ENGINE *can* make it smoother and reduce tranny hesitation. Here's why:
The compression ratio of the RX engine is like 10.4 or something, which is about requireing 91 octane to avoid detonation. However, the car's computer (ECU) can use a trick: retarding the ignition timing and downshifting to reduce detonation (knocking). This technique is effective enough that the RX's ECI can allow 87 octane gas to be used. The drawback is, with retarded timing, you get less power efficiency out of your gas. This is made up for (approximately) by downshifting, but as most 87 octane RX users experience, this means a rougher acceleration as the car double downshifts. (Annoying). In addition, the higher RPM's increase wear on the piston rings and journal bearings. There's always a tradeoff.
If you are 99% light on the acceleration, then 87 is probably better for you. It's economical, and since you don't demand hard acceleration, the car won't need to double downshift that often.
I only recently read about this, so I had been using 87 for the first 1.5 years of RX ownership. I recently switched to 91 (and feeling raped by gas prices) to see the difference. I must not have pulled the right fuse (or not long enough) because it still took awhile for the hesitation to reduce as the ECU adjusted the parameters.
My conclusion:
- 87 is just fine and even better if you are soft on the acceleration
- if you like to push the pedal, then you should move to 91 as that is what the engine was designed for. With 91, it will operate most efficiently (better power for acceleration)
- 91 won't affect MPG much (as I've experienced) unless you are doing a lot of stop and go city driving. Freeway driving will totally overshadow the 91 efficiency increase.
- medium octane, or 89 is the petrol industries joke, sorta. No car manufacturer is designing engines for 89. It's either 87, or 91 (for the USA, that is). If you're knocking at 87, try 89. But in most cases, it's either 87 or 91 that works best.
The higher octane 91 ON THE RX ENGINE *can* make it smoother and reduce tranny hesitation. Here's why:
The compression ratio of the RX engine is like 10.4 or something, which is about requireing 91 octane to avoid detonation. However, the car's computer (ECU) can use a trick: retarding the ignition timing and downshifting to reduce detonation (knocking). This technique is effective enough that the RX's ECI can allow 87 octane gas to be used. The drawback is, with retarded timing, you get less power efficiency out of your gas. This is made up for (approximately) by downshifting, but as most 87 octane RX users experience, this means a rougher acceleration as the car double downshifts. (Annoying). In addition, the higher RPM's increase wear on the piston rings and journal bearings. There's always a tradeoff.
If you are 99% light on the acceleration, then 87 is probably better for you. It's economical, and since you don't demand hard acceleration, the car won't need to double downshift that often.
I only recently read about this, so I had been using 87 for the first 1.5 years of RX ownership. I recently switched to 91 (and feeling raped by gas prices) to see the difference. I must not have pulled the right fuse (or not long enough) because it still took awhile for the hesitation to reduce as the ECU adjusted the parameters.
My conclusion:
- 87 is just fine and even better if you are soft on the acceleration
- if you like to push the pedal, then you should move to 91 as that is what the engine was designed for. With 91, it will operate most efficiently (better power for acceleration)
- 91 won't affect MPG much (as I've experienced) unless you are doing a lot of stop and go city driving. Freeway driving will totally overshadow the 91 efficiency increase.
- medium octane, or 89 is the petrol industries joke, sorta. No car manufacturer is designing engines for 89. It's either 87, or 91 (for the USA, that is). If you're knocking at 87, try 89. But in most cases, it's either 87 or 91 that works best.
Last edited by TunedRX300; 08-21-05 at 04:08 PM.
08-29-05, 04:28 PM
#55
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don't know about all the scientific stuff, but i personally use premium..i noticed that ever since I've been putting that stuff in my car, it rides smoother and my car starts up easier in the morning..i particularly use V-Power by shell..and sometimes chevron techron. I don't know about increased mileage or that other stuff, but bottom line for me is the car starts up easier and i get better response on the highway. 
11-20-05, 07:25 AM
#57
This is a very interesting thread. Since we've had our '00 RX300, we've used premium gas (91). I'm not sure why I started using premium from day 1, other than that's what the dealer said was Lexus's recommendation.
So after reading this thread I went to our RX300 owner's manual. And there it was, on page 247: Fuel Type Octane Rating 87 (research octane number 91) or higher. And on the inside back cover: Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating 91 (Research Octane Number 96) or higher is recommended. This is also shown on page 248.
So I feel pretty stupid right now for running premium since 2000. As of today, we're switching to regular 87, unless I hear knocking. If so, we'll move up to 89. Since this is my wife's car, I probably will not be able to compare gas mileage results from 91 vs. 87 octane.
Thanks for the great thread!
So after reading this thread I went to our RX300 owner's manual. And there it was, on page 247: Fuel Type Octane Rating 87 (research octane number 91) or higher. And on the inside back cover: Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating 91 (Research Octane Number 96) or higher is recommended. This is also shown on page 248.
So I feel pretty stupid right now for running premium since 2000. As of today, we're switching to regular 87, unless I hear knocking. If so, we'll move up to 89. Since this is my wife's car, I probably will not be able to compare gas mileage results from 91 vs. 87 octane.
Thanks for the great thread!
11-20-05, 06:17 PM
#58
Originally Posted by DaveJ
This is a very interesting thread. Since we've had our '00 RX300, we've used premium gas (91). I'm not sure why I started using premium from day 1, other than that's what the dealer said was Lexus's recommendation.
So after reading this thread I went to our RX300 owner's manual. And there it was, on page 247: Fuel Type Octane Rating 87 (research octane number 91) or higher. And on the inside back cover: Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating 91 (Research Octane Number 96) or higher is recommended. This is also shown on page 248.
So I feel pretty stupid right now for running premium since 2000. As of today, we're switching to regular 87, unless I hear knocking. If so, we'll move up to 89. Since this is my wife's car, I probably will not be able to compare gas mileage results from 91 vs. 87 octane.
Thanks for the great thread!
So after reading this thread I went to our RX300 owner's manual. And there it was, on page 247: Fuel Type Octane Rating 87 (research octane number 91) or higher. And on the inside back cover: Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating 91 (Research Octane Number 96) or higher is recommended. This is also shown on page 248.
So I feel pretty stupid right now for running premium since 2000. As of today, we're switching to regular 87, unless I hear knocking. If so, we'll move up to 89. Since this is my wife's car, I probably will not be able to compare gas mileage results from 91 vs. 87 octane.
Thanks for the great thread!
11-20-05, 06:21 PM
#59
Nope
Originally Posted by parula
Yea and we are saving money at these prices - glad I don't have a Beemer - don't they require premium?
- GRL
11-20-05, 06:25 PM
#60
Regular is the rcommended fuel for...
Originally Posted by CarsFreak
Is that true? That means the 3.3L was designed to run on regular? Than what's with the premium recommendation?
I'm trying to figure out the ugly milege I'm getting with the 3.3L. Maybe it's because I'm using regular.
I'm trying to figure out the ugly milege I'm getting with the 3.3L. Maybe it's because I'm using regular.
Anyone ever tried it?
My 330 i got 20.5 mpg city with premium and it gets 20.5 mpg city with regular.