jgrooms

Paul is absolutely right. To elaborate:

The energy content of gasoline is not determined by the octane number. Octane only effects gasoline's tendency to detonate (or burn). The higher the octane, the less likely for detonation to take place. Detonation is very destructive so it is important to control this property of gasoline.

Engine designers like high compression ratios because high compression engines produce more power from the same size, weight, etc. High compression ratios also produce conditions that cause gasoline to detonate more quickly. Therefore, the compression ratio is an important factor in determining the minimum octane requirement of the gasoline used.

The LS 430's high compression ratio demands the use of a higher octane fuel. Using lower octane will cause the fuel to detonate before peak compression has been attained (even with timing adjustments - which can only adjust so far). Not only is the overall performance compromised, but the long term use of low octane fuel can cause extensive (and expensive) damage to the engine as well.

IronCobra

Someone should send this to Mythbusters

KINGLS430

On the inside of my gas cover it says use premuium fuel only don't know why you wouldn't

Rare1

Most of the time you'll notice a decrease in mileage when you use a lower grade fuel than recommended. The engine will sound a little rougher after continous use. It's tempting using lower grade but I'd rather make sure my car runs to it's best potential, and the right fuel has a big part to do with that.

bippU!

im too poor not to get the best . . . .

GRAND_LS 4

iTrader: (2)

Here is a website with good info, so we can lay this matter to rest:

http://www.cartalk.com/content/featu...estions.html#4

bluegsx

same as I use to say with my Supra...if you have a car that costs THAT much...why go cheap with mods/gas? $30k-$60k for a car and people say "i'll use this because it will save me $10"...doesnt make sense... I use premium, I dont want the computer holding back ANY timing

wcl77

I"m sure there has been previous discussion on this topic however I would appreciate input as to whether preminum unleaded is really needed. I own an 02 and have recently done mileage and performance checks on the last 7 fills (4 87 octane regular unleaded and 3 91 octane preminum unleaded). I have not noticed any difference in performance or gas mileage. A rep at my local Lexus dealer said the company line is to use premium however the computer chip will adjust to either fuel and no damage will occur. Any thoughts will be appreciated.

Boomer01

Check out this thread:
https://www.clublexus.com/forums/sho...d.php?t=152749

miniz

gas (regular 87) destroy anything on an LS430? I've had Mercedes and they are very specific in letting you know that anything besides premium is forbidden. Mercedes claims it will significantly reduce the life of your catalytic converters and be harmful to your overall engine health. With gas prices out of control, I'd like to run the LS mainly on regular, then toss in a tank of premium every now and then. I understand the performance might be hindered by a slight amount and it might reduce overall mileage, but will it actually harm the car by running it on regular?'

And yes I have done a search and couldn't find anything specific to my question.

Thank you!

litesoarer

May i suggest using a half/half of premium/regular? (If your premium is 93 or above.) It will render similar mpg/performance as full premium.

As far as full on regular goes.

Do not do it. You'll just lose performance, and MPG. (enough MPG to make premium cost the same.)

Altitude also plays an important part..

blacksc400

iTrader: (4)

ENGINE KNOCKING KNOCKING...

what will you really save?? 2-3 dollars per tank?
to me, it's not worth it.

twojayzee

It will do the same thing to the lex...
edit: I should clarify that. Its not going to destroy your motor in one tank, but it has been proven to degrade cats,o2's and cause more sludge build up over time.

X2 in the grand scheme of things what do you pay 75-80 bux for mid grade so at 82-85bux per tank for premium. Whats a few more dollars to know what when you hit the gas your ecu doesnt have to retard your timing etc...

LEX012006

I used 87 in my 400 all of the time, for almost 1000,000 miles and I had no problems o2's or the cat converter. When I got rid of it to purchase my 430 (hell of a car!!!!!!) it was still running very good. But as blacksc400 stated, how much are you saving per tankful? My 430 is way too valuable to me to even possibly risk any long term damage, not to mention since it is a UL, a much better car. Besides that I making a little more money now so why take the chance. But if you must, the manual states you can use 87 octane, "IF" 91 octane is not available (Sunoco carries 91 octane). Therefore as per the manufacturer, you can use the cheaper stuff, but only once in a while. NOT all the time!!!!!

Tee

Here is my take on this, Lexus designed the LS430 to run off of "Premium" period! It has it stamped on the gas door in all caps "ONLY", and like LEX012006 quoted from the owners manuel "IF" 91 octane is not available for emergency cases only. So that tells you right there what you should use, the LS is not a disposable car, it is a high end vehicle, that takes high end gas! There is a saying--Pay me now or pay more later. This will hold true when you start blowing 02's and other issues arise. Premium burns cleaner & slower thus less trips to the pump, putting reg in it will burn faster due the trash in it and you will be back at the pump before me. You will get the knocking, loss of power (hesitation) when you step on the pedal along with much lower mpg. (clearly not why i bought the car for) It's not worth it in the short or long run IMO, it's your car not ours so it is your choice in the end.