NYKnick101

Page 4
http://drivers.lexus.com/t3Portal/do.../04gx40/62.pdf

The manual says 87 or higher so I would think its safe! You may notice some performance differences with the lower octane but it shouldn't be noticeable really in the GX

tftimm

I'm not too worried about performance, just hope I don't have knocking or timing issues...but as you say, based on the manual, everything was originally calibrated for 87 octane.

NYKnick101

Knocking you would only have to worry about with higher compression engines but if the engine was designed to run on 87, you shouldn't have to worry about knocking or timing issues

burny

Wow, My other 2 Lexus Sedans require 91 or better. Always assumed it was same for GX. I never even looked.

lesz

I've had my 2l005 GX since it was new, and I've been using 87 octane regular fuel in it since I got it. During that time, I've never seen a single instance of engine knocking or any other issues. Most of my driving is on rural roads, and I do very little driving in stop and go conditions. Driving on the country roads, my typical summer fuel economy has been between 20 and 21 mpg (from actual computation and not from the vehicle's computer). In the extreme cold of winter, it has gone down to about 17 or 18 mpg, but those numbers have held steady over the 9 years that I've owned the GX. I allow for the fact that there may be some minor loss of HP with the regular fuel, but, if there is, it isn't enough that I would even notice it. I can't imagine that I would have been doing any better with mpg had I been using premium fuel, and during that time, I figure that I've saved about a thousand dollars in fuel costs.

lesz

In the manuals for a couple (older) Lexus vehicles that I've owned, it has said that 91 octane is "recommended", but it also says that 87 meets the requirements of the vehicle/engine. With those vehicles, just like with the GX, I've used 87 octane regular, have had no engine knocking, and have had fuel economy well above what the EPA ratings were for the vehicles.

I also find it interesting that, with Toyota/Lexus engines that have been used by the manufacturer over the course of several years, the "recommendation" was for 91 octane years ago, but, now, for the same engines, it is 87 octane. For example, the 3.5 liter engine used in the ES has been used since 2007. At that time, the recommendation was for 91 octane. For the same engine in the current generation ES, the recommended octane is 87.

I've read numerous reports saying that the 91 octane recommendation was primarily to have a lower emissions level and to qualify for a higher EPA emissions rating, but, for the actual requirements for engine performance, 87 was sufficient.

chiph9

I wonder if E10 fuel was as common 8-10 years ago when the manuals were written. It has lower energy content that straight gasoline. Which is why I run premium now - to compensate for it.

Chip H.

IanB2

'03 + '04 GX470's are recommended for 87 octane, the '05+ with the vvt-i are recommended to run premium.

RCsGX

The 91+ octane started in 06+. In '05 they still recommended 87+.

Fact of the matter is you can run 87 octane if ANY year GX or you can a higher octane in ANY year GX if you want. Unless towing there's really no reason to use a higher octane gas in our 2uz-fe engines....

lesz

The manual for my 05 GX says that 91 octane is "recommended for improved performance" but that using 87 octane is sufficient.

RCsGX

Pic taken straight from the back cover of my owners manual.


In '06+ they say to use 91+ but you can temporarily use 87 if you can't find 91+:
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).

Which is complete B.S. since the '05+ VVT-i engines are EXACTLY the same. Again the fact of the matter is you can use 87 octane OR you can use a higher octane but using a higher octane, unless towing, is a complete waste of money.



EDIT: I see you edited your comment. So again, it says to use 87, which is what I said to begin with. The "extra performance" is for towing.

RCsGX

And just an FYI, even if you switch to a higher octane and can feel a difference in power, the ECU will retard the timing within a few miles so you will be wasting your hard earned money on a higher octane gas.

lesz

Yes, I edited my post to more precisely reflect what the manual says. In any case, my reading of the different wording in the 05 and 06 manuals is that they both essentially say that 87 octane is fine, but that performance may be improved with 91 octane. As I said earlier, if I've been using 87 octane in my 05 since the day I bought it, if I haven't experienced any knocking or other performance issues whatever, and if my fuel economy has been above the EPA fuel economy rating for the vehicle, I can't see any reason whatever why I would want to spend $.30 more per gallon for gas.

ZoeZhe04

iTrader: (9)

Ever since I owned my 04 GX470, I always fill up with 87 octane. It's been 6 years now with NO problem.

RCsGX

Fuel selection '06+:
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).

From reading the '06 manual above and how it states you can "temporarily" use 87 octane if you can't find 91+, I would be very hesitant on using 87 octane gas if I didn't know any better. It's making it sound as though something bad will happen if you don't use 91 octane on a regular basis which is nonsense because as most of us know, our engines do perfectly fine on 87 octane, whether it be a non or VVT-i.