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2004 GX470...can I switch from 93 octane to 83?

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Old 05-08-14, 03:22 PM   #1
tftimm
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Default 2004 GX470...can I switch from 93 octane to 83?

When I bought my 2004 with about 104K, I assumed since it was a Lexus it needed Premium, so for the last 20 months, I have been putting in premium.

Well, for no reason, I'm comparing gas mileage and it says that I should be using Regular. So, should I go to 91 for a few tanks, then 87 or is it OK to go straight to 87, or fill up now when I have 1/2 93 in there, and then switch, or could end up causing problems with timing, etc. since it has been running premium the last 2 years or so? I don't know what the previous owner was running, it was a 1-owner vehicle before I bought it.

At about 120K, the car runs solid, smooth, no oil drips, etc.

Saving $0.30 a gallon, $6 a tank a tank or so. I actually read that 87 octane will give you the best mileage, 93 will give you the best performance...come on, its an SUV, I'm more worried about gas mileage.

Thoughts?
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Last edited by tftimm; 05-08-14 at 03:26 PM..
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Old 05-08-14, 03:28 PM   #2
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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
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Old 05-08-14, 03:39 PM   #3
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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.
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Old 05-08-14, 03:46 PM   #4
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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
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Old 05-08-14, 03:48 PM   #5
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Wow, My other 2 Lexus Sedans require 91 or better. Always assumed it was same for GX. I never even looked.
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Old 05-08-14, 03:50 PM   #6
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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.

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Old 05-08-14, 03:59 PM   #7
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Quote:
Originally Posted by burny View Post
Wow, My other 2 Lexus Sedans require 91 or better. Always assumed it was same for GX. I never even looked.
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.
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Old 05-09-14, 07:05 AM   #8
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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.

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Old 05-09-14, 08:34 AM   #9
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Quote:
Originally Posted by burny View Post
Wow, My other 2 Lexus Sedans require 91 or better. Always assumed it was same for GX. I never even looked.
'03 + '04 GX470's are recommended for 87 octane, the '05+ with the vvt-i are recommended to run premium.
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Old 05-09-14, 11:29 AM   #10
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Quote:
Originally Posted by IanB2 View Post
'03 + '04 GX470's are recommended for 87 octane, the '05+ with the vvt-i are recommended to run premium.
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....
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Old 05-09-14, 11:36 AM   #11
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Quote:
Originally Posted by RCsGX View Post
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....
The manual for my 05 GX says that 91 octane is "recommended for improved performance" but that using 87 octane is sufficient.

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Old 05-09-14, 11:53 AM   #12
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Quote:
Originally Posted by lesz View Post
The manual for my 05 GX says that 91 octane is "recommended" but that using a minimum of 87 is sufficient.
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.
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Old 05-09-14, 12:14 PM   #13
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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.
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Old 05-09-14, 12:17 PM   #14
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Quote:
Originally Posted by RCsGX View Post

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.
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.
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Old 05-09-14, 12:40 PM   #15
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Ever since I owned my 04 GX470, I always fill up with 87 octane. It's been 6 years now with NO problem.
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