What Octane Gasoline For sc430? Premium fuel required? (Merged threads)
06-15-20, 04:41 PM
#211
Pole Position
I use 91 octane gas in my SC per the manufacturer's recommendation, as I want to get the max HP out of my engine. I would not be afraid to use 87 octane in a pinch, but would expect less max HP while doing so. Could substituting cause damage, especially if done on a regular basis? I don't know, but I wouldn't want to find out the hard way! My understanding is that modern vehicles have enough engine sensors and controls to adjust to a lower grade fuel without harm. Retarding the ignition timing should prevent un-burned fuel from harming the cat (while lowering HP).
Regarding Marvel Mystery Oil: I doubt the benefit of running it in the gas. How can adding a high-carbon product with a lower octane rating than gas "clean carbon out of an engine?" Show me the science! I've heard it is a good additive for older engines designed to run on leaded fuel as it lubricates the valve stems and seats. For cleaning carbon, a solvent designed for that purpose is best.
Regarding Marvel Mystery Oil: I doubt the benefit of running it in the gas. How can adding a high-carbon product with a lower octane rating than gas "clean carbon out of an engine?" Show me the science! I've heard it is a good additive for older engines designed to run on leaded fuel as it lubricates the valve stems and seats. For cleaning carbon, a solvent designed for that purpose is best.
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CCC-TT (06-15-20)
06-15-20, 06:56 PM
#212
Lexus Test Driver
I have had multiple Lexus master techs speak to me about this be a potential cause. I had cats fail on a my LS400 prematurely and the previous owner ran 87 its whole life. Anyway, it's a theory and I can't personally prove it. But it does make sense that less than ideal combustion leads to more fuel not getting burned and hence degradation of the catalytic converter system. If you think it is ridiculous than more power to you. Keep running 87. If you don't understand how pulling timing works to prevent knocking and how this creates a less than ideal combustion within the cylinder than read up about it.
However, your car can run perfectly fine (particularly in cooler weather) on 87 without it pulling timing. BUT that's gently driving the car and preventing any significant load (ie not flooring it, not lugging up hills, etc)
You can even hook up engine diagnostics and see the knock sensor activating.
And, while anecdotal, I had a Supra tuned for 94 octane and 22lbs of boost. 87 would surely cause catastrophic failure if driven hard. But I found myself in the middle of nowhere once, needed gas..and all they had was crap 87. As long as I drove it gently and stayed out of boost...the car was fine. Knock sensor didn't activate once.
I run 91+ on my Lexus car. Mostly because a) it's not prohibitively expensive b) I like not worrying about driving the car "gently".
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CCC-TT (06-18-20)
11-10-23, 05:17 AM
#213
Premium fuel
What is the consensus on premium fuel, I use it in my 04 ls430, it says too, my 5.7 Hemi Ram, and also know in my 03 SC, it doesn't say, that I have seen anywhere yet ???
11-10-23, 05:20 AM
#214
Premium fuel
What is the consensus on premium fuel, I use it in my 04 ls430, it says too, my 5.7 Hemi Ram, and also know in my 03 SC, it doesn't say, that I have seen anywhere yet ???
11-10-23, 06:11 AM
#216
Use the octane that is recommended by Lexus. It's listed near the gas port.
11-10-23, 06:34 AM
#217
11-13-23, 03:08 PM
#221
Lexus Test Driver
I have heard every Lexus is premium.
not sure if they all need it.
not sure if they all need it.
11-13-23, 03:10 PM
#222
Lexus Test Driver
Here is the same thread with over 200 comments
https://www.clublexus.com/forums/sc4...d-threads.html
https://www.clublexus.com/forums/sc4...d-threads.html
11-14-23, 07:17 PM
#223
Instructor
Octane has nothing to do with HP. It is a measurement of the knock resistance and your car will not have more or less HP. It also is not some kind of super solvent that keeps the tank/engine clean. It is only a measurement of the fuels ability to resist knock at high compression. In modern cars, since about 2000 there is a knock sensor that adjusts the timing to prevent knock. In the absence of high octane fuel, it will prevent knock. If you are not abusing your car with a lead foot, lower octane will work fine. AND if you are abusing your car with a lead foot, why are you worried about what damage lower octane will cause. You are already abusing the car!!!!!
11-15-23, 05:50 AM
#224
Octane has nothing to do with HP. It is a measurement of the knock resistance and your car will not have more or less HP. It also is not some kind of super solvent that keeps the tank/engine clean. It is only a measurement of the fuels ability to resist knock at high compression. In modern cars, since about 2000 there is a knock sensor that adjusts the timing to prevent knock. In the absence of high octane fuel, it will prevent knock. If you are not abusing your car with a lead foot, lower octane will work fine. AND if you are abusing your car with a lead foot, why are you worried about what damage lower octane will cause. You are already abusing the car!!!!!
MGF spec is premium fuel. That is what a company is recommending that has literally put more hours into testing than we can in a single life time.
I'm not a Toyota engineer but I would venture to say the ECU has been set up for 91 octane just as Mercury has set up their ECU for the 496 HO for 87 octane.
Following manufactures suggestions would be your safest bet.
11-15-23, 05:55 AM
#225
Octane has nothing to do with HP. It is a measurement of the knock resistance and your car will not have more or less HP. It also is not some kind of super solvent that keeps the tank/engine clean. It is only a measurement of the fuels ability to resist knock at high compression. In modern cars, since about 2000 there is a knock sensor that adjusts the timing to prevent knock. In the absence of high octane fuel, it will prevent knock. If you are not abusing your car with a lead foot, lower octane will work fine. AND if you are abusing your car with a lead foot, why are you worried about what damage lower octane will cause. You are already abusing the car!!!!!
Thanks,