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What octane gas do you use? (The Mother thread)

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Old 02-14-12, 04:20 PM   #181
Lavrishevo
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Stan,

The knock sensors and computer controlled timing are just as active whether you are running 93 or 87. It's not like it's something that turns on only if you run 87.

Damage to an engine is caused by prolonged predetonation. If the computer adjust the timing to prevent it there is not adverse effects besides less power. Personally, I run premium but I if the car runs on 87 without predetonation then it does not hurt the engine whatsoever.
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Old 02-14-12, 05:10 PM   #182
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Default I recommend the highest octane.

Quote:
Originally Posted by thermal View Post
The recommended is premium unleaded, but with the price of gas going up, do any of you 'cheat' and use regular?

Will it harm the engine to use lower-octane gas?
I use the highest octane I can get, around here it's 90 sometimes 91. It's not that much more compared to the performance and taking care of the engine. I recommend the highest or buy a different car!!
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Old 02-14-12, 05:19 PM   #183
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Quote:
Originally Posted by Lavrishevo View Post
Stan,

The knock sensors and computer controlled timing are just as active whether you are running 93 or 87. It's not like it's something that turns on only if you run 87.

Damage to an engine is caused by prolonged predetonation. If the computer adjust the timing to prevent it there is not adverse effects besides less power. Personally, I run premium but I if the car runs on 87 without predetonation then it does not hurt the engine whatsoever.
I realize that. Car has no clue what octane fuel you've put into it (or if it's even fuel), it has to rely on the knock sensors.

Here is a link to the PDF that discusses features of the 1UZ-FE in detail. Search for "octane", you'll find a flowchart of the logic the ECU uses for knock correction. Snippet:

Quote:
Knocking Correction
The ignition timing at which engine knocking occurs differs according to the fuel octane value. The ECU controls the ignition timing at the optimum timing to correspond to the fuel octane value.
If engine knocking occurs, the knock sensor converts the vibration from the knocking into voltage signals and sends them to the ECU. The ECU judges whether the knocking strength is at one of three levels; strong, medium or weak, according to the strength of the knock signals and changes the corrective ignition retard angle. That is, if knocking is strong, the ignition timing is retarded a lot, and if it is weak, it is retarded a little.
When engine knocking stops, the ECU stops retarding the ignition timing and advances it by fixed angles a little at a time.
If ignition timing advance continues and engine knocking recurs, ignition timing is again retarded. The ECU feeds back signals from the knock sensor to correct ignition timing as shown below.
I'd prefer to not have my ECU constantly running in the loop of pulling back timing/re-learning slowly, but that's just me.

It also specifies that the engine is designed to run on 96RON (92 in US equivalent).

Stan
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Old 03-13-12, 11:46 PM   #184
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Running a full tank of 87, I notice my car has really sluggish acceleration. That's all I need to know to know to not do it again.
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Old 03-14-12, 02:12 AM   #185
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The 430 guys have one going too. If curious:
http://www.clublexus.com/forums/ls43...um-merged.html
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Old 03-14-12, 07:42 AM   #186
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It's pretty simple really IMO.
If your car is retarding the ignition to prevent detonation the engine isn't running at peak efficiency so you are getting worse gas mileage.. You may save at the pump but you will get less miles out of the gas. Better to just give the car what it was designed for.
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Old 03-15-12, 12:54 PM   #187
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Default LS400 and LS430 Regular gas.

I buy hi mileage cars because to me it sense. I use regular gas exclusively. No pinging ever.
I very seldom step on it but when you do the 05 is really fast and no ping. I get around 20 mpg
in each.
Mileage; 98 212500
05 115200
Both black all the way
I had a 88 735 IL fast but expensive to operate. put 225,000, sold it to a CHP officer.
Lexus ever since.
In the 98:
The oil in my power steering is dark brown and growing???
The tranny is pink and growing????
I've had it serviced at an independent shop, (used to,). Now I have oil, pink, on garage floor
one day and the next day or two I get dark brown. Two problems?

I've worked on cars all my life but can't figure this out assuming the shop did the right amount of fluids.

Last edited by Andyb9000; 03-15-12 at 01:01 PM.. Reason: an addition
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Old 03-16-12, 10:31 AM   #188
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I have ran 89 and 96 at different times and really dont see any difference in mileage or performance, but I am not a "take off fast" driver anyway... I use the same in my 96LS & and the 99LS.
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Old 03-16-12, 11:52 AM   #189
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Bottom line is, all engines are designed with specific octane in mind for operating properly. It is simply physics, nothing else. You can "cheat" if you live at really high elevation as physics change due to air density changing.

If you choose to operate your car against how it was designed (even the gas cap says "premum" on it), then be it -- it is your car. But, be aware that what you are doing goes against the initial intend of the engineers who designed and built the car, that's all. You don't know something those engineers didn't know about the car, and there is no conspiracy in them requiring you to use more expensive fuel.

People who argue that using high octane fuel is a waste of money are simply wrong, plain and simple. I used to be one of those people until I got into the aircooled scene, and then purchased a turbocharged car.

Stan
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Old 03-16-12, 12:18 PM   #190
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I agree completely with what you have written, and do not elevate my knowledge above theirs or even yours. but at 77, I dont have many more years of driving ahead of me, and knowing of the superb quality in the Lexus LS, I dont feel like I am ruining a motor for the owners that follow me.

OH, I dont do it simply to save money, but as I said, comparing the two grades in my own cars, I dont see it as necessary..
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Old 03-16-12, 12:30 PM   #191
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I totally agree -- the fact that these cars stand up to running lower grade fuel without any apparent issues speaks volumes about their quality. Turbocharged Subaru would crack a piston or spin a rod bearing, and even the non-turbocharged ones, designed to run on 87 knock when it is used, and stop knocking on premium. This info is from owners of brand new Subarus.

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Old 03-16-12, 10:07 PM   #192
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Just use what your manufacturer recommends. You are driving a lexus here...You want to save money on gas, go buy a 4 cyl.
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Old 03-17-12, 04:26 PM   #193
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Where I live 93 octane is $4.10 a gallon so I feel your pain with the cost of gas but you do drive a "High End" vehicle so use high octane gas. I know in certain states (cali,co,pa,ect) the highest octane is generally 91 which is what the minimum stated requirement is according to Lexus so it will work perfectly fine as well. I would never put lower than 91 octane in my vehicle personally, IMO Lexus would not tell you to use it just for kicks and giggles.
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Old 03-17-12, 04:50 PM   #194
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Quote:
Originally Posted by thermal View Post
The recommended is premium unleaded, but with the price of gas going up, do any of you 'cheat' and use regular?

Will it harm the engine to use lower-octane gas?
I have owned a beautiful 1997 LS400 coach edition for about 5 years. I have used regular ever since I bought the car. I have never heard a "ping" and I get 20mpg city and somewhere between 26 and as high as 31 highway. I have never understood why it varies on the highway so much. I generally hold it at 70mpg on the interstate. I baby the car--no fast takeoffs ect. I spend extra money on synthetic oil. So far my only repair is an up-stream oxygen sensor. I got it for $36.00 online. I am convinced that only people that put their foot to the floor on takeoffs need to use premium. I can't imagine why anyone would want to drive an LS400 that way. Drive your car sensibly and use regular. My car has 217k and still drives and runs like a dream.
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Old 03-18-12, 10:07 PM   #195
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I'm in Missouri, and all gas has at least 10% ethenol, which is NOT good for my 25 year old Porche and a real concern. So....

How is ethenol working out for Lexus? I've been buying premium at a Casey's stations and getting about 22mpg. We just got this car on the road 2 weeks ago.

Will the contnued use of 10% cause an issue? Some companies are using ethenol as a cheap road to higher Octane (which makes sense since the ethenol burns slower than gasoline), Will this be a problem for my 94 LS400 with ~200k?

I've heard rumers that MO will be - or aleady has - mandating at least 15% Ethenol.....what will that bring?
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Old 03-18-12, 10:07 PM
 
 
 
 
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