I just drove from Indianapolis, IN to Charleston, SC and back. The NAV (trip computer) calculated 23.5 for the trip. My hand calculations were 22.7. Cruise control was set at 75 most of the time.

 

My 2014 RX350 AWD MPG is improving after 4,000 miles.

•Two tanks of 87 octane E10 gas - 100% city driving in Cape Coral and Fort Myers, FL yielded 20.1 and 20.5 measured MPG respectively.
•Trip from Cape Coral to Valdosta, GA also 87 octane E10 gas 95% highway measured 25.3 MPG.
•Trip from Valdosta, GA to Dalton, GA, 87 Octane E10 gas yielded 28.3 measured MPG. I should also note that this last trip was interrupted by six stop & go traffic back-ups lasting for 5-25 miles due to road construction on I-75 and 285 around Atlanta.

It appears that my MPG is improving as the car learns my driving style and gets broken in a bit.

 

I am so jealous.

 

Jim routinely keeps data on his gas mileage and did so before with his 2nd Generation RX as well. He seems to be always ahead of the curve when it comes to obtaining high MPG numbers. I will point out that I too have driven those sections of road many times. I usually try to hit the Atlanta area early in the morning, around 3AM, in an attempt to avoid the traffic. Not a convenient start time here, but I am about two hours further north of Jim's starting point for this trip. Without the traffic you can get pretty good gas mileage.

 

I have noticed a variable not often mentioned in this thread. I believe wind can have a dramatic affect on the mileage of an SUV or van. I would think as little as a 15 mph headwind or tailwind, could dramatically influence gas mileage over a 300 mile trip on the interstate. I wouldn't know how to quantify this, but I would guess the affect might be as much as 10% (2.4 mpg?).

 

Keeping the cruise control off gives me better mileage also, to much down shifting to keep speed up.

 

We are now just over 4000 miles:

 

500 miles 14 rx. mostly highway driving and the computer says 16.9. last fill up i used 93 octane for the hell of it. any tips? My wife drives it mostly and she does not have a lead foot. sort of baffles me

 

I've just hit 1k miles. Mine has gone up to 17.7 in heavy city driving on regular, which is about what our '04 gets. Yours should get better with time

 

Great point about the wind being a factor in mpg. I also think weight is a factor. If I am in car alone I can expect about 2-3 mpg more than in the car with 3 other adults. I also took off the roof cross rails and that added another 1 mpg. Also, since talking with my service advisor about the quality of the gas and the frequency of clean filters has had an effect. Using the gas line cleaner helped, but only temporarily. Build the price of that into the formula and it is a negative gain. But it did work for a short time. My overall mpg combined this winter has been 22.3 on my 2010 RX using 87 octane. This discussion has effected my decision to trade in for a 2014. Why take a chance if there are problems out there.

 

I set my cruise at 75. The only time it ever downshifts is when I drive through the mountains. I am sure it would downshift just as much without the cruise, unless I was willing to "crawl" up the mountains behind some semi.

 

I am just reaching 31k on my 10' I drive a consistent 80% local,20 hwy in NY Queens, Brooklyn type roads (pothole/red lights/random emergency stops, the works!) with 91/93 octane fuel I've always hit 22-23 mpg.

 

Can we also post avg speed as well. For example mine is currently 14.5l or 16mpg and avg 35kph or 22mph

 

They need to update the drivetrain. Most others (including some Toyotas) now utilize high pressure direct fuel injection which increases both power and fuel economy. And numerous other marques offer 8 speed transmissions now for more of those same two benefits. The top of the line Lexus drivetrain is becoming outdated.

 

April 26, 2014, Auburn, CA to Lake Tahoe, CA, 87 octane, apx. 200 miles, over Donner Summit, cruise on and off, 23 mpg, '11 RX.
Christmas card scenery. Note the Golden Retriever Rescue special edition moniker.
Ray A