I have 2 AWD Questions

[pawprint]

Forgive me if this has already been discussed, but I didn’t see it.

I have a 2010 Nissan Rogue SL AWD.

1. The AWD models are to get 1 MPG less than the FWD models. I don’t understand why. From what I’ve read, the AWD for the Rogue is “intuitive”. The vehicle functions and drives like a FWD until there is wheel slippage, and then the computer activates the AWD. I believe my Rogue is in FWD 98% of the time. I don’t understand why AWD would drop fuel economy when it’s not being used. Does it weigh a lot?

2. Does anyone use the AWD lock button? The manual says this will turn the AWD on for the duration of my trip. I thought it would be an added measure of safety to turn the AWD on when I have a snowy commute; however the manual says “No”. When should I use it, if ever?

Thanks in advance,Pawprint

[philipa_240sx]

Hello pawprint,

I am quite familiar with the Rogue's AWD system so here is an explanation:

1. The AWD models are to get 1 MPG less than the FWD models. I don’t understand why. From what I’ve read, the AWD for the Rogue is “intuitive”. The vehicle functions and drives like a FWD until there is wheel slippage, and then the computer activates the AWD. I believe my Rogue is in FWD 98% of the time. I don’t understand why AWD would drop fuel economy when it’s not being used. Does it weigh a lot?

There are a few factors that explain the loss in fuel economy:

1) The AWD system has a computer controlled clutch that disengages the engine from the rear differential and wheels during FWD mode. Even though there is no power sent to the rear wheels in FWD mode, all of those spinning components (the drive shafts and diff) create a bit of drag on the rear wheels and decreases fuel economy.

2) The extra weight (about 160lbs worth) requires more power to accelerate.

3) Anytime the AWD system is engaged, more power will be needed to accelerate than FWD mode. The system actually engages far more frequently than most realize:

- During initial acceleration from a dead stop until the system detects it's not needed. - Anytime the the vehicle is not travelling straight ahead, ie sharp corners and accelerating.

The AWD system in the Rogue is quite sophisticated and is the result of over 2 decades of development on cars like the Nissan GT-R. It uses steering wheel angle sensors, lateral g-force sensors, and individual wheel speeds to vary the power going to the rear wheels from 0 to 50%. The system reacts in milliseconds... long before the tires start to slip. This makes it superior to many passive systems which allow the tires to slip before engaging the AWD.

2. Does anyone use the AWD lock button? The manual says this will turn the AWD on for the duration of my trip. I thought it would be an added measure of safety to turn the AWD on when I have a snowy commute; however the manual says “No”. When should I use it, if ever?

The AWD lock button switches the system from fully automatic to a 50:50 power distribution. I would not use it with the assumption that it will 'work better' in all situations. It's meant to be used in difficult situations where the automatic system cannot cope and you need more control:

- Heavy deep snow, muddy roads, sand- Stop and go driving in heavy snow.

Even if the AWD button is ON, the system will still disengage the AWD lock at highway speeds and also to protect the system from damage, overheating, etc.

Finally...

I tell this to everyone who has an AWD/4WD vehicle:

- AWD/4WD does not improve traction! It's purpose is to distribute power to all 4 wheels and use all the available tire traction to accelerate better.- The quality and type of tires is the largest single factor that determines how much traction you have.- AWD/4WD does little to improve the cornering or braking capabilities of the vehicle.

[pawprint]

Thanks for your answers and they make a lot of sense.

I traded my 2006 SL AWD Murano for the Rogue SL AWD. The Rogue AWD seems different than the Murano’s. (Probably because it was 4 years old and out of date)

You are absolutely correct about the importance of tires and the braking/cornering of AWD.

** Yes, I’m guilty of feeling more secure during rain & snow because of AWD, and I drive faster than I should….I’m always tempted to get in the fast lane behind the other SUV’s during inclement weather and zip on by. But isn’t that why we pay extra for our 4WD / AWD SUV’s? So we can “safely” zip through bad weather?

When Mother bought her SUV, she said, “I did not spend an extra $2,000 to sit in the slow lane during a snow storm!”

Pawprint

[philipa_240sx]

But isn’t that why we pay extra for our 4WD / AWD SUV’s? So we can “safely” zip through bad weather?

That line of thought is why some SUV drivers end up in the ditch. Or worse yet, cause an accident and injure or kill somebody. I used to think this way and I've changed my outlook completely... age I guess?

However, I still relish driving in inclement conditions. I find it a challenge to balance the vehicle and keep it pointed where I want to go. Making it through a big snow drift or driving down that unplowed side street gives a sense of accomplishment I guess.

Be smart out there and always drive within the limits of your ability and road conditions. To do otherwise is foolish.