LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

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

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Old 02-06-06, 03:56 AM
  #31  
ychachad
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93 only. Although with extremely cold weather or high altitude, the appetite for higher octane is reduced. As gas prices get higher and higher, it makes more economic sense to put in 93. Percentage wise, 93 octane gets closer in price to 87 octance.
Old 02-06-06, 08:18 AM
  #32  
MadMax96
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I've been putting in 89 octane (mid-grade) in my '99 since I got it. The previous owner said that's all he put in it and the car runs great. If I detect any issues I will immediately switch. I'll put in a tank of premium every once and a while though..

In my previous car, a 2002 Maxima SE - it, too, required premium. For the first 18-20 months I religiously put in the 91/93 octane (whatever was the highest at the station I stopped at).

When chatting with the head service advisor at the stealership about the rising fuel costs he said I could put in the mid grade... so I started to do that. I couldn't detect a change in how the car performed or behaved...and I did drive the car hard.

So as long as you don't have any knocking I'd say you guys could probably try mid-grade and be fine.
Old 02-06-06, 08:27 AM
  #33  
mink92890
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I fill it up with premium. I do what lexus wants me to do lol.
If you dont put in premium, and something happens because of it, cant it void your warranty?


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Old 02-06-06, 11:32 AM
  #34  
MadMax96
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1999 LS400 with 118k miles = no warranty

The previous owner on mine purchased the car as CPO so he did have a warranty to worry about - apparently was never a problem.
Old 02-07-06, 07:24 PM
  #35  
austxlexus
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I have done 91 and 93...and 93 got me better running and 4 more miles per gallon.

So, I always use 93.....Texas!
Old 02-07-06, 10:33 PM
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You aren't saving -any- money. Fill up with each grade of gas and do a mileage comparison. The lower the octane you use, the lower the mileage. In the end, you will pay the same amount to achieve the same per tank if you used premium.
Old 02-08-06, 08:33 PM
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thermal
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Why is it that the lower the octane, the lower the mileage?
Old 02-08-06, 10:16 PM
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not entirely sure but im pretty sure that the higher the octane, the more completely the fuel is combusted, which means less fuel is required to get the same amount of power. this means that the car uses less fuel since the engine's overall combustion efficiency is increased.

higher octane>more complete combustion>increased efficiency>more power/unit gasoline>less gasoline used per unit power required to move X distance.
Old 02-09-06, 01:08 PM
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There is no correlation when comparing 91 octane and 87 octane in terms of complete combustion, however, there is strong correlation between higher octane and resistance to detonation. Gasoline octane scale is a method to measure resistance to detonation (and nothing else) relative to the pure gas octane (C8H18) which arbitrarily assigned the octane of 100.
Old 02-09-06, 01:41 PM
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lexsee
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the reason you can run lower octane and notice no change is because you have the knock sensor that keeps the engine from pinging and/or detnating.
Old 02-09-06, 08:36 PM
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BACKNBLACK
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Default what octain do you use.

if you are short in the cash dept. try this. STP octain boost or any high octain booster gas additive. I go to walmart so i buy the three pack and add them periodically.
I cant allways fill my tank but when I do then I figure Im saving at least 15 to 20 $ on at least a 40 $ tank fill. am I the only one that does this? secondly I only notice a difference in the station to station gas like for instance... the A-plus or Surf gas opposed to the Exxon or Mobil.
Thats just my way of thinking what do you think?
Old 02-10-06, 11:22 AM
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austxlexus
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Originally Posted by BACKNBLACK
if you are short in the cash dept. try this. STP octain boost or any high octain booster gas additive. I go to walmart so i buy the three pack and add them periodically.
I cant allways fill my tank but when I do then I figure Im saving at least 15 to 20 $ on at least a 40 $ tank fill. am I the only one that does this? secondly I only notice a difference in the station to station gas like for instance... the A-plus or Surf gas opposed to the Exxon or Mobil.
Thats just my way of thinking what do you think?
Not understanding your fuzzy math??? You say "save 15-20 $ on a $40 tank fill? That is 45-50% savings???"

In texas there is only a .20 cent difference between 87 and 93.

Thus: Low octane 87 @ 19 gallons = $41.80

High octane 93 @ 19 gallons = $44.65

Low octane saves= $2.85 per tank or approx: 6.5%

High octane fuel effiency= 3-4 miles extra per gallon = 15%+ MPG economy!
Old 02-10-06, 01:20 PM
  #43  
2006lx470
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big als cheap gas

regular unleaded (85)
Old 02-10-06, 10:58 PM
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Bottom line is there is no way to get around the lower performance from the lower octane rated fuels. The electronic pooter fuel management curves alter engine performance if you use a lower rated octane. Get on the gas and see for yourself. If you don't feel the difference with the timing retarded by the sensors, your car is out of tune and has other issues to fix.

I'll put in the gas as recommended by the manufacturer because that is what the engine has been calibrated to run on.
Old 02-11-06, 02:14 AM
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Bigkahuna
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Having fun with my kick butt Premium at $3.13 a gallon. Last nites pump from costco premium gas was $66.00


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