sprocket

^^^^ Is that picture from the 2004 Owner's Manual?

BlackCat81

Let's clarify this once and for all. NEVER, in the history of all mankind, has octane rating had ANY effect on fuel economy. EVER. NEVER. Octane is just a fancy way of describing a way to avoid detonation. The lower the octane, the faster it burns. The higher the octane, the slower it burns. GX's equipped with NON-VVTi engines do not require premium fuel. Mine is an 03 and does NOT have that decal in the fuel door, and does just fine with 87 octane. There's so much drama on this forum about fuel octane and this and that. It's just plain unnecessary. It's not like there's some magic "octane sensor" in our fuel tanks that miraculously know what fuel is being added. If for some strange reason your truck begins to detonate, a knock sensor is in place to retard timing to avoid damage. A knock sensor's sole purpose is to detect abnormal engine vibration, and in no way, shape, or form is connected to any vehicles fuel system.
And in addition, the term "premium" varies from state to state. That picture that states "premium fuel only 91 octane" is not premium fuel here in IL. That would be mid-grade. Premium for us is 93 octane.

UpStarr

No drama! Just stick to the dealer recommendations. If it says" Premium Only" then use "Premium Only". If it say 87 or better then use 87. Plain & Simple. If you buy a hi-end luxury vehicle do not expect to cut comers without ramifications and do not expect others to approve of it. We own an M5, CLS550 & the GX and this is common amongst many owners of luxury vehicle. The octane gas question always comes up and some people will always say that high octane is unnecessary. I’ve read all the data about detonate, knock sensor, blah blah blah. Stick to dealer recommendation

shyguyF

Why don't go with the premium fuel as it recommended just costing you a lunch meal from 87 to 91 or 93 for everytime of filling up the tank.

cassman

THANK YOU for all of your opinion's, the senses appears to be somewhat split. I guess, as a rule follower myself I'll keep putting premium gas in this truck. That said tho it seems to me I heard a news story years ago that stated buying premium gas for any vehicle was like buying a extended warranty for your washer and dryer (not necessary). Again thanks for your replays.

BlackCat81

There are vehicles that do need premium fuel. Compression ratios, timing curves, and application dictate what is appropriate. Putting premium fuel in a car/truck that doesn't need it makes about as much sense as wiping before you poop.

Barnesie

I have an 04 and the manual specifically states that premium fuel is NOT required. I believe someone already mentioned it, but non VVT engines - which includes 03 and 04 GXs - do not require premium fuel. For what it is worth I have put premium fuel in my 04 and I cannot tell any miilage or performance difference. If you have an 03 or 04 just save the money and run regular fuel.

YoshiMan

non-vvti 2004 here as well. No premium sticker on the fuel door, and the 2004 manual states to only use premium for "maximum performance"... Which also being located in Colorado myself, i can tell you that a 2004 model year 2UZ-FE is fine on mid grade, especially at this elevation.

I wouldn't put regular in it though. Midgrade or better

IanB2

Another '04 owner here, I've tried premium in the past and didn't notice any difference, so it gets regular 87 octane. If I had a newer one with vvt-i I would likely put the premium in it.

techrep

09 owner here...never put anything higher than 87 oct. in it... runs like a champ.

shadowmite

As far as I am aware, the only reason Lexus dictated the premium only was to bump up the low emissions rating they could from the vehicle. While some here are claiming Octane doesn't have an effect on fuel economy it most certainly can. But it works backwards of what you might expect. Higher octane means the fuel has more stable and lower energy additives. As a result, it gets worse economy (typically not very noticeable). Those same additives have the side effect of making the emissions better since you are getting less real fuel per cylinder explosion.

I've been running 85 octane or whatever the lowest is called since I bought my 2006 and it's working just fine with no problems. That said, if you have to pass an emissions test that refers to the OEM rating, you MIGHT have issues without premium.

HaywardLex

Probably an old subject, but which fuel do you use regular 87 octane or premium 91 octane. I recently bought a 2005 and have run both and can't say I noticed any difference. The Toyota 4 Runners with the same engine runs regular but my Lexus manual says premium. WHICH grade do YOU use ?

chiph9

I use premium for around-town driving since I want the performance to be able to pull out into traffic. If I'm taking a long highway trip I'll use regular, since constant 70mph driving doesn't need the power.

Chip H.

techrep

we use 87 oct. all the time.. we have all kinds of performance..

HaywardLex

I have talked with a few people that claim better mileage using premium, but I can't say that I experienced any difference. The HP rating stated in the manual for the 2005 is higher than other years so I thought maybe that's why specified premium. I haven't noticed any ping either using regular, but I haven't pulled a trailer with any amount of weight yet. Was thinking the computer would compensate anyway.
Checked on some of the Toyota forms (they use the same engine) and they seem to think it's just because Lexus promotes the "Premium" concept of the car, so it must have to use premium fuel LOL. Guess I was interested to see how many owners on here used premium over regular. Myself I'll run regular but maybe once in a while run a tank of premium if I'm towing.