jjscsix

ill bet $100 that in a blind test between identical cars, one with premium and one with regular that nobody on the forum will be able to tell the difference and there would be no surging or hesitation. In fact, that doesn't even make sense if anyone really understands the what the fuel grades actually do. And I have the experience in my wife's GX above to prove it, and it's not the only vehicle I've experimented with both grades. The worst case is the engine "pulls" timing which has a very minimal effect on throttle response and peak power. And by throttle response, I don't mean hesitation.

bclexus

Under full throttle I think you would notice the engine building toward maximum torque and horsepower and then suddenly taking an unexpected dive in performance as the knock sensor alters the engine's timing...and you would likely feel some continued jolts or quiver in the engine's performance like the ignition system is malfunctioning, which is the knock sensor dithering back-and-forth between sending a signal, and not. Driving normally under a light to medium engine load would almost certainly not give any indication of a difference between regular and premium gasoline.

Continuously activating the knock sensor over a period of time will throw a Check Engine Light (code), which is something most people would find to be irritating, if not troubling.

SW17LS

Bottom line is, the engine operates its best on 91+, not sure why someone would go to the expense to buy a Lexus and then not get that vest performance to save a few dollars.

bclexus

Totally agree...

jjscsix

i dissagree. It's not a sudden pulling of power, it's very subtle. And a knock sensor does not throw a code, it simply adjusts for the fuel. Anyone want to come ride in our GX460? You pay me $100 if you feel anything, I pay you $100 if you do. I'm not making this stuff up or guessing. I've tried it. Zero difference that can be felt.

And saying that 91 octane is best is based upon trust in what Lexus is telling you. It's only best if the car needs it. It's a long known fact, and science, that a car runs better on lower octane unless the car NEEDS a higher octane to prevent pre-detonation.

bclexus

There is absolutely no doubt that you are much better informed and know better than Lexus engineers - but I thought I'd share this ► LEXUS REQUIRED MINIMUM OCTANE RATING ◄ with you nevertheless.

Also, Lexus specifically answers the question ► Can I use a lower octane fuel in my vehicle than what is recommended to save money? But again, you disagree with the obtuse Lexus engineers that designed these lowly machines...

sam430

iTrader: (10)

Try 90% water and 10% 87 octane gas, that might save fuel. (btw, don't do it).

jjscsix

Did you read one of my earlier posts about the engine in our GX being the same as a Tundra engine, and the part when I said I was skeptical? I don't for a second claim to be smarter than Lexus engineers. But I'm smart enough to research FACTS and actually try something myself to see what happens. The fact is that TOYOTA builds identical engines for two vehicles, both on truck platforms, both similar weights, both similar tow ratings etc. But one they rate for premium fuel and one they rate for regular. Go ahead and look it up. Like I said, I didn't believe it either when a guy posted that on the GX forum. But give me credit for taking the time to look it up because he was right.

Please explain to me how that equates to how much their engineers know that I don't know. Engineers are not always the ones who decide how to market vehicles. I can picture engineers dictating that an engine will be adversely effected by too low of an octane. But I can also see where a vehicle could be rated a higher than needed octane for marketing reasons because running higher octane has no negative effects from a reliability standpoint.

SW17LS

It's pretty simple. The engine will be fine, but it will not operate as intended by the engineers on regular fuel. You may or may not notice that difference, it will depend on the model, probably the individual engine, and you and how you drive.

My thing, and the reason I haven't even tried regular in my LS and didn't in my GS is that I bought an expensive luxury car and I want it it to operate as well as it can. I don't understand why I would even try the wrong fuel to save maybe $30 a month when I'm forking out $1,000 a month to drive the thing.

bigblack06

iTrader: (20)

This always seems to come up every year in regards to what gas can I use, although I have not tested this theory in my own car I have been in cars such as a BMW X5 and a Lexus RX350 these two require 91 octane When I decided to use a lower grade gas such as 87 octane the mpg and distance tell empty changed dramatically. I think if in a pinch yes its ok to use 87 or 89 octane but over time it does not help the engine.

jjscsix

I agree with everything you just said. And to be clear about where I stand, I have never put less than the rated octane in a vehicle before what I shared above about the engine in our GX. And I should also point out that my wife does not drive it hard at all, so I had no issues running a few tankfulls through to see how it felt. What I've been doing is running two tankfulls of regular in a row to be sure I've purged the premium out so I could get a really good feel for it, then I run a tank full of premium.

bclexus

I would certainly think that Lexus would be all-too-pleased and very quick to announce that only 87 octane gasoline is required IF 87 octane was sufficient. Why in the world would Lexus want to require a higher octane gasoline than is really necessary? They wouldn't! There is absolutely nothing to be gained by Lexus requiring a higher octane than is really needed...

Dkp1111

At the end of the day, it is your car,your money, you can put whatever you want on it. If it is break down then it is your money to fix it. There are people take good care of their car and the car still running good @300,000miles. On another hand, I see quite a few car break down at 50,000 miles.
Car is just like human body, you eat healthy food & you work out you will last longer 😁

jjscsix

You have conveniently ignored my posts about the engine in our GX. Care to weigh in on that one? The guy on the GX forum thinks Lexus rates them for premium as a perception issue so that Lexus owners feel like they are getting better engines in general. I have no idea where the truth is in all that, but I know for a fact that they recommend different gasoline octanes for the exact same engine, except that it actually puts out more power in the lower octane model (the extra hp is likely due to a less restrictive exhaust in my opinion).

Here is a link to the thread on the GX forum I'm referring to....
https://www.clublexus.com/forums/gx-...7-gx460-3.html

bclexus

First off - I couldn't care less about the engine in your GX - this is the GS 4th Gen forum. As for the guy on the GX forum who 'THINKS' Lexus rates them (a particular engine) for premium gasoline as a 'perception issue' so that Lexus owners feel like they are getting better engines - this is more than just laughable - it is a downright stupid belief. You say that you have no idea where the truth is. Come on man - I know you're smarter than that - you should know better than to believe such nonsense! Have I regarded you to be more intelligent than I should have?