Keep in mind that your LX is filled with regular gas by the dealer, at delivery, as it is the only fuel they carry in their tanks. Premium requirements are mostly for obtaining that magic mileage rating for EPA purposes.

 

Nothing like a good necro thread to start the day off.

Just an observation or two...

RXOwner is correct. Lexus may recommend premium, as that's the gas they used to get their CAFE numbers. If <91 octane is used, the truck will adjust it's settings without operator input over the course of a tankful or 2. In fact, Toyota suggests 87 octane for the current Land Cruiser...same drivetrain. Lexus has something like 2 hp more, and that's all. The Lexus also has about 1000 lb. less towing capacity than the Land Cruiser.

I run unleaded 90 octane...that gives me a minimum of 10% more gasoline. Non-ethanol currently runs around $2.80 a gallon. I do not track mileage on a 3-ton truck, I know going-in that she's not a Prius. The first thing I did was to turn off the "ECO" light and I drive with the "Power" button on, except in slippery winter weather.

 

I would guess that LX 570 requires premium fuel just for marketing reasons (premium SUV must require premium fuel...). It looks that there is absolutely no difference between engines at Tunda/Sequoia/Land Cruiser and LX.
When I asked Lexus why, they answered that "Despite engine specifications being similar to that of Toyota models, our current Lexus LX model was engineered to be a high octane gasoline engine." We all know that this is a lie.
I tried to get an answer here at this forum at Lexus Customer Service. I tried to ask twice but they never answered. They probably do not want to tell such lies here. On the other side, they cannot tell you the truth. There is always a risk of class action lawsuit - some LX owners could want the money paid for the Premium fuel back :-)
BTW, I think that the towing capacity has nothing to do with the engine, just with the suspension. It's similar to Sequoia Platinum towing capacity difference.

 

Just read the March 2016 Edmonds.com article about premium recommended versus premium required. Surprisingly, the LX is one of only 3 Lexus vehicles on the premium recommended list -- the vast majority of Lexus vehicles are on premium required. Still, I've always used premium and will continue. Big Daddy lives at 7,000 feet and likes to take us to play high up in the Rockies. We'll be enjoying the results of this weekend's winter storm on Mother's Day. I've had no mechanical problems in 70,000 miles and get better than average gas mileage, so I'm happy to spend a little extra on fuel. I don't cheap out on dog food or on Big Daddy. On the other hand, I still like to brown bag PBJ sandwiches to the office. And, from the messages earlier, I shouldn't have come home griping today that premium at our Shell station went up to $2.63 a gallon.

 

Really? I thought it was basically required Premium or regular unleaded. The RX350 is regular recommend, Rx450H Premium required. Interesting

 

Edmunds is wrong - see the Owner's manual for '16 LX570.

But please, tell me just one good reason why I should use premium on LX570. The Owner's manual is not the reason. It is the same engine as in Tundra/Sequoia/Land Cruiser. There is also no mpg difference. I tested it on a 200 miles route a few times. Actually, I got 0.1-0.2 better mpg with regular.

There are engines which were designed to use premium fuel - for example 4.6 V8 in my LS460. I would strongly prefer to use premium fuel for these cars although using regular probably cannot harm them. But 5.7 V8 at LX570? Why?

 

It is the same reason why someone would spend $97K on a car.

 

I think at the end of the day, one does what one pleases. If you feel better using premium gas, then fine. If you are Ok with regular gas, then that's Ok too.

For our prior LX470 before we traded it in after 280K+ miles and some 13 years. We pretty much used only regular gas and had no issues. But for our new LX570, we just use premium gas as recommended even though we know we probably can get away with using regular.

 

I think that there are many good reasons to buy LX. If you need a reliable and off-road capable car which is also comfortable for everyday driving and fits your large family, there are not many other choices. Just one - Land Cruiser. And there are some good reasons to pay more and buy LX instead of Land Cruiser: Mark Levinson, adaptive suspension, adaptive cruise control with full speed range (Land Cruiser works for >25 mph only), powered rear gate, better leather, probably also better seats... It just make sense to spend more for LX.
But I still cannot see any reason why I should use premium fuel. It's just wasting money for absolutely nothing.

 

The only outlandish reason would be that a fuel system issue presents itself one takes the vehicle for warranty work, dealer can claim customer used incorrect fuel causing accelerated wear and thus warranty denied. Again fuel sampling is common place these days when high $$ warranty work is required but the chances of the a Toyota engine even needing it is highly small in probability and unless the manual states premium required then yeah use whatever grade you like

 

Seeing that my dealer and likely most other fill your tank with regular at delivery time, it would be hard for them to void warranty for regular gas.

 

Prove it.....is what likely is going to be said to you when you charge them with that. Same way aftermarket mods sometimes is used against customers by dealership to deny warranty work. You can of course prove it, but its just an additional hassle for the end customer.

Again without going into this deeper, just a likely reason why warranty work can be an outlandish reason to use premium. I say outlandish since how many thread posts have been about Lexus Fuel system problems....nil

 

Now that I think about it, I remember hearing horror stories, real or urban legends, about how some
German car dealers service departments gave a hard time to people who used regular fuel in their cars(not the recommended premium), and how it caused all sorts of engine problems, and warranty issues. Also, my Land Rover... when check engine light came up the first thing I was asked by their service was if I was using the right fuel. None of it may be an issue with Lexus, but ....

 

I agree that the discussion is useless as there would not be a warranty problem because of the grade of gas.

 

I'm positive of two things in this thread. First, all the above are opinions. Second, no one here has any direct knowledge of how the code is written for the engine management system for any of the cars referenced.