bgsntth

Maybe it is just me, but I switched during the fuel price spike from 91 to 87 and did not notice any hesitation, pinging, or general roughness as a result of using the cheap stuff; however, I did noticed that at full throttle above 4K RPMs, the truck felt markedly more strained and had less power. My wife, the primary GX driver, just putts around our hamlet, so I like to "clear the carbs" when I get to drive the GX on weekends. I usually just fill it with 89 now, except when I plan on driving on the freeway at speed for long trips or off-road.

kurtman

I work for an oil refinery. There is a BTU gain in burning 92 octane vs. 87 but not worth the extra money. If your car doesn't ping on 87, you don't need anything else.

The research octane number is the octane results in the lab and is higher than the motor octane where they actually test it in an internal combustion engine. In Hawaii, the octane sold at a retail station uses the (R+M)/2 method or (Research Octane / Motor Octane)/2.

GGGXXX

I think Toyota would not make the 92 octane statement if there was a not a valid reason for 2006.....all the peformance data they quote in their brochure also has a footnote that it is based on 91 octane and they state that anything lower willLOWER performance....

Besides only 20Cents difference vs premium in 87 vs 92 so around $4+ per fillup - - a fillup per week would get your $200+ / year.... I think GX owners can afford that for the added performance...

BobsGX

Up here, the difference between 87 - 93 octane is usually 30 cents a gallon.

kurtman

Again, I work for an oil refinery. The BTU you gain is not worth the 20-30 cpg (cents per gallon). If the 2006 engine has higher compression than the 2005 and prior, then there is justification for the higher octane by the manufacturer.

Does the 2006 manual say 92 Research Octane (RON) or 92 Motor Octane? 92 RON is about 87 Motor. 97 RON is about 92 Motor Octane.

These are the specs that are typically tested for motor gasoline:
Octane
Aromatics
Copper Corrosion (some storage terminals also require silver corrosion due to the increased use of silver components in electronics such as the fuel sending unit)
API Gravity
Distillation
Gum
Sulfur
Reid Vapor Pressure
Olephins
and sometimes BTU.

BTU is the measure of energy. Although BTU is greater in 92 than 87, it is not significantly so.

kurtman

One of the octane myths that was pushed by Exxon in the 90's what that older engines need higher octane to run better. However, older cars tend to have looser rings and lower compression and would not need higher octane. Exxon had to pay a fine and post brochures at their stations about the "truth" about octane.

Here's a thought: some refiners have started to "super-additize" their premium, meaning they add 50-100% more than the required dosage of additive to their premium vs. regular. In theory, this will reduce carbon buildup in the head as well as keep injectors cleaner. In theory. Perhaps this is a reason for the switch.

Or maybe because other luxury cars such as Volvo, BMW, and Mercedes requries premium, Toyota thought they'd better keep up with the Rockerfellers.

The G Man

I would not think that a premium gas requirement is a selling point for Lexus or anybody, in fact, it is the opposite considering the price of gas now a days. Toyota is such a conservative company that if they require premium gas, there must be a good reason for it.

SilverLady

This whole change doesn't seem to make much sense in the real world. 2005 is basically the same as 2006, and isn't the Toyota 4Runner V8 (which I am told can use regular) the same engine in 2006?

My guess is that they needed to optimize something just a smidgen to make the numbers (probably horsepower, torque or pollution) look slightly better. MPG in particular is shown rounded to the nearest mpg, so the difference between 15 or 16 mpg can be much smaller or bigger than it looks. The HP took a hit between 2005 and 2006 because of the way it was measured, and the 470 found itself at a disadvantage. If any of these numbers could have been nudged even a tiny bit by recommending premium, they would do it.

From the point of view of truth in advertising, if the test numbers they report are with premium gas they better "recommend" premium gas - even if the vehicle works just about as well with other gasoline. Otherwise they are setting themselves up for a nasty class action lawsuit, government fines in 50 states and a hit in reputation down the road.

For all I know they suddenly discovered the vehicle needs premium, or they fine tuned the computer to take it in 2006, but my consumer marketing experience says there is a bit more than that.

The G Man

Toyota recommands 91 octane in the 4runner V8 too.

kurtman

I guess there are shades of difference in "recommends" and "requires".

I6turbo

iTrader: (1)

Just for the heck of it I calculated the mileage on a few tanks of 87 octane and a few tanks of 93 octane fuel. The results for the various tanks are shown in the format of:
Octane / Average MPH / MPG per the computer / Actual MPG

93 / 27 / 20.1 / 17.25
87 / 32 / 20.0 / 17.4
87 / 25 / 19.0 / 16.1*
87 / 26 / 19.1 / 16.2*
87 / 26 / 18.4 / 15.9
93 / 26 / 19.1 / 16.7
93 / 27 / 18.6 / 16.2

*Shell gas. All others were Chevron
The on-board computer is consistently very optimistic.

BobsGX

Those things are always optimistic. No matter who the manufacturer is.

gs400jon

The MPG calculator on the ES330 is within a tenth of hand calculation. The MPG calculator on the GX is 2 MPG on the high side.

The G Man

It would be interesting to see if after a few more tanks of 93, will the MPG go back up to 17.25.

Josh's GX

Were the driving conditions all the same for each tank of gas? Also, has anyone noticed better gas milage from certain gas stations such as Shell, Exxon, Chevron, Mobile, or grocery stores?