bsekf

First long trip with our new-to-us 2011 RX350. I have been using regular gas (83 octane) and have not been excited with the MPG. A week before our trip I started using hi-test (93 octane) about 2 tanks full, thinking this would give the computer time to adjust. Left WNY, cold, no wind and dry roads,on-board computer says 21.3 mpg. First fill up with 93 octane and the mpg remained at 21.3. Second fill up with REGULAR (83 octane), still cold, no wind but wet roads, mpg goes up to 21.7. Third fill up with regular (83 octane),same conditions and mpg goes up more to 22. I continued to use regular gas and by the time we got to Florida our mpg was up to 22.5.

Exactly opposite to what I expected. This was not a scientific experiment, I have no idea if all the gas had 10% ethanol or if the trip computer is accurate, however the wet roads should have decreased the mpg and they didn't. Needless to say, I am buying regular for my RX350!

Anybody had a similar experience?

kitlz

bsekf, I suggest you take a look at the mileage thread on top of this forum. In there are other members' experiences using various octane levels. Just keep in mind the octane level requirement dropped from premium to regular beginning with the the 2012 MY except for the 450h.

jfelbab

Don't overlook the affect that winter blended fuel has on fuel economy. I saw an immediate 2 MPG drop in MPG when reformulated (winter) fuel hit our pumps (2014 RX350 AWD). There are so many variables to take into account. Fuel type, octane, air temp, wind, rain, traffic, elevation, etc. I've done a few tanks of mid-grade (89 octane) and saw a very slight improvement but not enough to justify the $0.20 a gallon increased cost. Regular seems to run fine in my RX.