I came to this thread wondering the same thing (although mine isn't an F Sport). My salesman made much of the fact that this vehicle takes "regular" unleaded fuel, which was a novel concept for me since my last car was an Audi and I've been programmed to use premium.

I just looked it up in my manual and it does say that the only requirement for the RX 350 is for an octane rating of 87 (different story for the 450H). However, it does warn against using flex fuel or anything with 10% or more enthanol, which may limit the grades of suitable fuel available to me in my area.

I'm really puzzled after reading the previous postings in this thread... did the requirements change that much from MY 2010 to MY 2013?

As I said, I'm quite used to using premium and have no issues whatsover using that if it's beneficial for the vehicle.

 

Yep, you dug this thread out of the archives. The 2010 through 2012 models are recommended 91 octane only. For the RX350 it changed in 2013 to 87 but not for the 450h which still requires the 91 octane.

 

Hi Jim,

Didn't want to create a new thread so pulled the old post up. So would you think it's better to keep using 87 on the MY'13 RX-Fsport or better use 89 or 91? It wouldn't really hurt right, or the engin would not burn as efficiency on the 91?

 

It's always best to go by the manual or the decal inside the filler door.

 

Lexus changed to 87 since 2012 model. The 2012 model only lasted a few months.

 

Thanks Jim.

Any idea is if they changed the motor from prior '13 or most likely ECU tuned and made it capable to run 87?



All F-Sport owners - are you guys following the guideline or of using 87 or you guys are using 91 just to be safe?

 

JS, thanks for posting your data and analysis.

I'm impressed that the computer MPG closely matches the actual you calculated!

 

Hi Jim,

Thanks.

 

Perhaps. I am under the impression, based on research and thread supported suppositions that ethanol read: corn, is potentially harmful to the Rx350 v6. By its design, 87 octane gas has a higher probability of containing ethanol. 91 or higher octane contains no ethanol. Hence, I would err on the side of caution and use 91 or higher as stated directly in my 2011 manual until Lexus and a big if an update bulletin is placed conferring appropriate regrade to 87 octane fuel. Fuel for thought.lol

 

That is technically incorrect. There is ethanol in most all gasoline these days to include 91 and 93 octane fuels. You can even get 100+ octane fuel with ethanol in it. I know this because I have to be very careful about which fuels I can use in my classics and farm equipment. Actually, by adding more ethanol to the fuel mixture the octane rating goes up. "Where the octane number is raised by blending in ethanol, energy content per volume is reduced."

http://en.wikipedia.org/wiki/Octane_rating

To find fuels in your area without ethanol you can search here:

http://pure-gas.org/

Ethanol fuels with 10% or less ethanol in them (E10) are not a problem when used in the RX350. The major downside is the lower MPG numbers (see quote above). There may or may not be problems, however, should this value be increased to 15% (E15) as currently being discussed to be made law replacing E10. E15 is currently available in some areas of the US. So, be sure to inspect the pump before you fill.

http://www.fuel-testers.com/state_gu...anol_laws.html

http://www.popularmechanics.com/cars...t-e15-15096134

Ethanol is hygroscopic which is why it cannot be piped to locations like gasoline and must be transported by other means such as rail tankers or semi trailers. Another potential problem for vehicle owners. Still, in many ways it is better than MBTE which was used previous to oxygenate gasoline. But the biggest problem with current ethanol production is the conversion of existing fields growing food grade crops to grow corn formulated for use in ethanol production instead of backing other methods for ethanol production such as from switchgrass. As a result food prices have gone up across the board since we are literally burning food in our tanks. And for that we have Big Ag to thank.

 

After your considerable and extensive knowledge I am so gratefully humbled. I appreciate your words of wisdom. Now if I could find 95 plus octane for the 11rx???? Hmmmm. Your thoughts on whether
I would achieve higher mileage with more octane?? Where to go in Portland, Oregon,USA?

 

So what, the dealership's cars have no friends?

 

Your 2011 RX would more than likely max out MPG-wise with 92-93 octane fuel without ethanol in it. As stated previous, you can go here to find locations in your area with ethanol-free fuel in Oregon:

http://pure-gas.org/index.jsp?stateprov=OR

Now, whether it is the most cost effective for you to run on a daily basis is something only you can determine. It is just not a straight calculation of what gives you the best MPG, rather, it is what gives you the best MPG for your dollar. If you have to drive across town to get ethanol-free fuel are you really saving anything?

 

I have a 2010 RX 350 and use regular gas. I have tried premium gas and have notice no difference. Nothing. Nada.
Same gas mileage and same performance. I believe the computer reads the octane delay and adjusts accordingly.
And the octane level has nothing to due with crappy gas. I believe that is a very naive understanding of gasoline. Octane rating does't effect anything other than burn rate. The higher the octane the slower the fuel burns.

 

I use 85 octane in our 2010 and it runs the same as premium. I truly cannot detect any difference. The 85 octane gas is sold here due to the high elevation.