I was next to an LS430 owner at the pump the other day and he told the attendant to use 87 octane. I just assumed that we needed to use 91 or above but then began to think that these are essentially toyota engines so what's the difference.

Besides a slight decrease in performance, does anyone have any insight?

 

If I'm not mistaken, for the past ten years just about every medium to high-end sedan has utililzed knock sensors that can retard the timing to avoid pinging. This is pretty much a guarantee on anything that asks for premium that was built since the turn of the century. Don't you feel guilty, though, about depriving your baby???

 

Do the math.
Lower octane = less mileage.
Less mileage = more fuel ups.

In the end of the day, you'll still be spending the same, or more amount of money than you would have if you just put in the high octane fuel in your car.

Besides with ony 290hp or so we need every hp us LS430 can get!!!

 

I was told 93 is the best for this car.

If you are leasing, maybe the last year of the lease is OK, but if you bought it and want to keep it for the 4 year warranty, I wouldn't mess around.

Not worth the few hundred you might save.

 

It really is a moot point anyway as the difference is only 20 cents per gallon (and my company pays for my gas anyway). I was just curious.

 

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The only time you might need to switch to a higher octane level is if your car engine knocks, if your car does not knock low octane is O.K. to use.

Unless your engine is knocking, buying higher octane gasoline is a waste of money, too. Premium gas costs 15 to 20 cents or per gallon more than regular. That can add up to big bucks every year. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.

What are octane ratings?
Octane ratings measure a gasoline's ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93).

What's the right octane level for your car?
Some cars with high compression engines, like sports cars and certain luxury cars, might need mid-grade or premium gasoline to prevent knock. Try the lower grade, if your car does not ping/knock, then spend the money you save on your wife or kids.

How can you tell if you're using the right octane level? Listen to your car's engine. If it doesn't knock when you use the lower octane grade of gasoline then keep using it.

Will higher octane gasoline clean your engine better?
As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should you ever switch to a higher octane gasoline?
A few car engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Is knocking harmful?
Occasional light knocking or pinging won't harm your engine, and doesn't indicate a need for higher octane. But don't ignore severe knocking. A heavy or persistent knock can lead to engine damage.

Is all "premium" or "regular" gasoline the same?
The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what you're buying, check the octane rating on the yellow sticker on the gas pump instead of relying on the name "premium" or "regular."

Will higher octane fuel increase my fuel mileage?
Not to the point you would notice the differance. You would need a fuel with an octane rating of 100 or more to greatley improve mileage and performace.

 

considering that LS engines were built for 91 octane, most of your points above are not correct. They might be correct in case your engine was built for 87.

Knock sensors, while useful, only retard the timing once they notice pinging. So for performance, mpg, emissions and engine longetivity reasons, you should use reccomended fuel.

 

Your points on listening for a knock or ping are completely baseless. The knock sensors will PREVENT knocking or pinging BEFORE they are audible. They do this to prevent engine DAMAGE. They do this by decreasing timing and adding in EXTRA fuel.

THIS ALWAYS RESULTS IN LOWERING FUEL ECONOMY AND PERFORMANCE. (it has to by definition)

I have always found that putting lower octane than what is required results in NOTICEABLY lower performance and LOWER fuel economy- My Escalade losses at least 1 mpg and does not have the same power, the same held true for both Lexus models I have owned.

As soon as you come to the conclusion that you are willing to lower the performance and fuel economy on a $70,000- $90,000 vehicle to save THREE DOLLARS, go right back to your dealer and see how soon you can get out of your car and go buy a Camry...

 

you can use 87, the computer will retard the timing so the car loses performance. and to cetain point the engine will start to knock. i don't remember what compression the engine is running at (i think v8 has slightly lower compression), but on cars like the is350, good luck on running anything lower than 91

and i hate to say, but 20 cents a gallon between 87 and 91, that totals to what? 500 bucks a yr? give me a break, if you own a car like this (60k at least) and can't afford 500 bucks extra a year? you got the wrong car

 

Beg to differ-you should not use 87 octane. The Lexus web site says the new V8 has the highest compression of any manufacturer-that is why they went to two injection ports so the engine would work on 91 octane. I believe they said the compression was something like 11.8 which is very high compared to the 10.5 of most V8s including the GS. (some of Lexus other new engines are also in the 11s). The computer will only retard to some degree then you get knocking, and with the quiet cabin you may not hear it and suffer engine damage as a result. Knocking will pit the pistons and cylinder walls and eventually deteriorate the rings with oil usage increasing.

Most gas stations have 93 octane as premium and 91 as their "plus". The manual says use greater than 91 octane-so why not fill up every other time with 93? I agree with another post, that in the long run 93 octane is the right stuff and with its increased mileage you probably break even.

You know the old saying about boats/yachts that also applies to luxury cars-if you can afford a $70K car-you don't need to ask about fuel costs.

 

Third or fourth time I've tried posting this with CL going down and up ...

As others have posted, your post is completely incorrect in parts and not correct in relation to the LS in other parts.

Specifically about the 'savings' for using cheap gas. Let's do the math again shall we?

Say 15,000 miles a year
At 20mpg that's 750 gallons
At .20 savings using 87 instead of 91 you'd save $150
About enough for 2 tickets into Disneyland I think.

And probably more than offset by the worse gas mileage you get because you won't hear knocking because the engine's too smart for that.

 

i only use 91 or higher now, but in the past when i was younger and money was an issue, saving a couple bucks ment i could have more beer money
i would use 87 on my 1'st gen gs and never had any problems, i was told i would lose performance and to watch for eng knoc, but i never got any of the above. but if money is not an issue use high octane

 

My post was a copy and paste from a U.S. Gov controlled research company. I guess the people who wrote that article are stupid and should consult you guys next time instead of spending all their money on research. I'm glad some can afford to throw $500 or more dollars a year out the window, some of us are not rich and it takes every penny we have to afford a nice car. I have owned at least 10 Lexus, never once have I heard one ping using regular gas. One of my cars had over one hundred and fifty thousand miles on it and not once was it in the shop using reg gas. So if your so rich instead of giving you money to the oil companys, please send it to me.

 

Maybe the best way to solve this is to ask this question again in a couple of years. Someone on the forum is bound to stick with 87 so we can ask the results then. As for me, I actually plan to keep this car for 5 or 6 years so I am not going to risk it.

 

I guess Lexus is stupid too then and just puts their recommendations in the manual to waste owners' money.

So you drive about 50,000 miles a year?

Those two statements are a bit contradictory unless you're buying old Lexus vehicles.

And as we've explained over and over, you WON'T because the engine is smart enough to retard timing to avoid knock when you put cheap gas in it. So sure it's likely to work for years without real problems. Knock yourself out.