lynhnn

For normal driving do we always get 100:0 ratio? if so why it would hurt gas mileage?
For wet driving (rain only) what ratio do we get ?

I want to know if my AWD get used at all? How do we know? or confirm? Any indication? Is it worth extra bucks or gas dollars?

I assume 2013 is the same as 2012 below:

The RX 350 AWD model features an electronically controlled Active Torque Control AWD system. Active Torque Control AWD uses an electronically controlled coupling ahead of the rear differential to vary torque distribution anywhere from 100:0 to 50:50 front to rear, depending on driving dynamics and road conditions. When accelerating, or starting off on a low-grip surface, torque is quickly provided to all four wheels. At steady speeds, torque is sent only to the front wheels, enhancing fuel efficiency.

To help provide handling agility and control, the AWD system increases rear-wheel torque when the vehicle’s front tires start to lose traction and decreases rear-wheel torque when the vehicle’s rear tires start to lose traction. On rough or sandy terrain, an AWD LOCK switch provides enhanced traction performance for low-speed maneuvering (if in LOCK mode, the system reverts to AUTO mode when speed exceeds 25 mph). To help prevent a tight corner-braking condition (shuddering) during low-speed cornering, the system reduces rear wheel torque.

from http://pressroom.lexus.com/releases/...ive+models.htm

waapples

My impression was that when comparing AWD to FWD model mpg, only 1 mpg difference between them, which is the result of the electronically controlled Active Torque Control system.

http://www.fueleconomy.gov/FEG/bymod...Lexus_RX.shtml
http://www.fueleconomy.gov/FEG/bymod...Lexus_RX.shtml

Marqevans

A good part of it has to be due to the extra weight of the AWD system.

waapples

Good point, I preferred AWD after test drove both, felt much solid and stable, and when I learned AWD & FWD mpg didn't make much difference, it was a no brainer.

Alpy64

differences come from the capabilities of the testers (road conditions, traffic, sensing of using hybrid, etc.).
The weight yes but the AWD has 2 electrical motors while the FWD only one then less capability in starting from "0" with the rear electrical motor particularly in winter conditions (snowy, icy condition, etc.)
To me AWD is much more secure and stable particularly during strong acceleration (mountain driving...)

waapples

hmmmm,,, I didn't know non-hybrid RX350 has electrical motors, thought electrical motors are only equipped on hybrid model RX450.

m1964

He might be thinking of electrically controlled differentials. In slippery conditions AWD will shift some power to rear wheels.

Alpy64

I said that when starting from speed = 0, rear electrical motor "pushes" the vehicle systematically and this has nothing to do with electrical control differential as the 'instant traction' does for Volvo xc70 / xc90.