According to what I have read, recommended fuel for the 2006 is regular, while it is premium for the 2007-2008. Has anyone with a 2007 or 08 used regular grade without any problems? Thanks.

Owner's manual for my 2006 RX400h states 91 octane RECOMMENDED (the other number given is the Research Octane Number (or RON) number which is 96, however the number on gas pumps is the 91), but says you can run 87 if you want.

Specifically it states: "
Fuel selection:
Select Octane Rating 87 (Research Octane Number 91) or
higher. For improved vehicle performance, the use of
premium unleaded gasoline with an Octane Rating 91
(Research Octane Number 96) or higher is recommended"

There is a difference between RECOMMENDED and REQUIRED.

I just checked online owner's manual for 2007 and 2008 and it doesn't say recommended anymore - it simply states "Use unleaded gasoline. (91 Octane rating [Research Octane Number 96] or higher)"

Pg 450 of my 2008 RX400h owner's manual states:

"Premium unleaded gasoline with an octane rating of 91 (Research Octane Number 96) or higher required for optimum engine performance."

Then below that it states:

"If premium gasoline is not available: If 91 rating gasoline cannot be obtained, you may use unleaded gasoline with an octane rating as low as 87 (Research Octane Rating 91)."

So according to the manual, 87 is still fine for the 2008. The main question is (assuming no engine pinging) is what does that do to the mileage? I think I read one thread where some claim to get better mileage with regular than premium, but that is counter-intuitive to me. I'll probably give it a try.

Edit: Here is the post: https://www.clublexus.com/forums/hyb...long-post.html
https://www.clublexus.com/forums/hyb...nd-of-gas.html

More maximum power and efficiency use the recommended rating. We use premium in our 06 RXh.

The HS 250h has a regular fuel recommendation.

Our '06 states we can use regular fuel but for more performace to use '91 or higher. So 89 octance is the lowest we'll go.