bcolins

I have been tracking my fuel mileage in my 2006 RX400h (with 181,000 miles on it) alternating between 87 octane and 91 octane fuel. I generally do 2-3 tanks of each. My driving is a mix of 40-55 mph with occasional time at 65-70 on major highways. Generally driving conservatively, with occasional harder acceleration to pass traffic or avoid something. I don't practice "Hypermiling", my tire pressures are 38 front and 40 rear.

My most recent findings: 87 octane: 24.3-24.7 mpg / 91 octane 25.5 -25.8 mpg.

willameena

Stick with regular if it’s not “pinging”. You make my AWD 350 07 RX jealous 😁

Grafito

I have been using 87 octane in my 2008 RX400H (224K), driving same as you mentioned. I get a combine of 26.7 mpg. Happy with that, but may try 91 octane in the future just to see.