ADVocate

You probably have the 2005 model that had the horsepower boost w/ VVT. I think the 2005 might require the higher octane for the better overall perfromance, due to the valve design. The previous models did not mention a preference for the 91 octane. I am not sure what the 2006 has put in their manuals, since Lexus also did a design change that dropped the horsepower again.
There was a thread discussed a while back in this forum, and it seem pretty much a personal decision to which octane people use. There is not an average "better result" from using the higher octane. Some found that the performance got snappier, but the overall fuel mileage went down (that sounds about right doesn't it ).

BobsGX

Lexus didn't make a design change which lowered the horsepower and torque ratings on the 06 models. The government changed the way all engines are to be tested and this either lowered or raised the engine ratings depending on design. If the 05 models were tested the way the 06 models are, the ratings would be the same.

caha14

From 2004 owner's manual:

GAS STATION INFORMATION
Fuel selection:
Select Octane Rating 87 (Research Octane Number 91) or
higher. For improved vehicle performance, the use of
premium unleaded gasoline with an Octane Rating of 91
(Research Octane Number 96) or higher is recommended.

From 2006 owner's manual:

GAS STATION INFORMATION
Fuel selection:
Select premium unleaded gasoline with an Octane Rating
of 91 (Research Octane Number 96) or higher for optimum
engine performance. However, if such premium type
cannot be obtained, you may temporarily use unleaded
gasoline with an Octane Rating as low as 87 (Research
Octane Number 91).

So that's our answer. It looks like the engine with VVT-i does prefer premium, though I wish they used less vague language. Words like "temporarily" don't make much sense in this scenario IMO. You can either run it on 87 or not...

Capirato

Here in California we have three choices of octane. The lowest is 87, which I use, The highest they call "Premium" and then the middle one which I can't recall the octane.

My conclusion is, the lowest octane for the older engines and the middle choice for the newer engines. With the preference of going up one notch on either one of the engines for best performance.

~ Cap

The G Man

I have a 05 GX which has the same engine as the 06. The manual saids:

Select Octane Rating 87 (Research Octane Number 91) or
higher. For improved vehicle performance, the use of
premium unleaded gasoline with an Octane Rating of 91
(Research Octane Number 96) or higher is recommended.

I wonder why Lexus change the wording on the 06 manual?

Capirato

Switch to 87 Octane

http://www.toyota-4runner.org/showth...?postid=106277

~ Cap

The G Man

Thats only the case if you run higher octane than recommanded, thats not that case with the GX.

bunka

This topic has been "beat to death" but one more time might not kill it so here is the summary...
87 Octane will provide you the best fuel ECONOMY
91 (or higher) Octane will provide you better PERFORMANCE.

This trunk is DESIGNED to run on 87. Running 87 does NOT harm the engine in ANY way. Reports of sulfur smell can ONLY be related to the mfg type of fuel burned, not the Octane (i.e. wally's cheapo gas - 87 octane may smell but 87 Octane from Exxon, BP, and Smart Mart, Petro Express, etc and even BJ's does not produce any smell in my GX470). Using 87 Octane I acchieved 23MPG on a 5 hour trip. Using 93 Octane the best I could achieve (on the exact same trip but different day with similar temps) was 19.7.

Mine is an '04 and does not have the VVT so performance may be different in the trucks witht he variable value timing .

lexguynj

I was part of that group that always filled it up with Super (highest octane), when gas prices went up and I was seeing $60+ tank refills with Super, I tried Regular (lowest octane) for the heck of it.

To tell you the truth, I can't tell the difference..... maybe I am getting worse gas mileage, but nothing else has changed. Maybe it's all a marketing scam!

BobsGX

I traded in an 05 GX and picked up a new 06 GX today. I noticed that the 06 has a decal on the inside of the fuel door which says to use premium unleaded. The 05 never had the decal.

The G Man

Hmmm any change in the engine from the 05 to 06, is the compression ratio the same?

lepoch

Hi--could you provide some citations for this statement that lower octange gives best fuel economy please? I have had better mileage in all my cars when I used higher octane, like 1-3 mpg more than when I used 87.

Thanks.

Kwoker

I know many folks reported better gas mileage when using Octane 87 vs Octane 91 gas.

I have a 2005 GX with about 2,200 miles. So far, I got around 18.5 miles/gallon with Octane 91 (premium).

However, when I switched to Octane 87 (regular), gas mileage dropped to 17 miles/gallon.

Any reasons why I got difference results?

The G Man

With 91, you get more compression with every engine stroke, hence, more horsepower and torque with same amount of gas injected. If driving style remains the same with 87 and 91. Using 91 should give you better gas mileage. The poeple who reported better gas mileage with the 87 are probably driving more aggressive while using 91.

TomGXer

I have the 2005 and use 87 octane. There really is very little difference between the different grades. Save your money.