My 2008 chev 4x4 has the "auto" 4 wd feature on it and thats what I leave it in except for actual 4wd use. I'm wondering if people have seen fuel mileage increases using the "2hi" setting?

Interesting question - I leave mine in 2hi - have a 2011 with the 5.3L V8 - what engine do you have and what mpg are you getting? I'm currently averaging 18.4 with around town mixed with short highway. 20.8 to 21.1 on hwy at average 72mph

I was told continuous use.of auto will cause t. case wear.

I ran my Tahoe in the "auto" mode anytime there was any type of snowy/slush on the way. I liked it a lot. I ran in 2hi when the roads were dry. The only time I used 4hi was when I was going off road at all, or even on logging roads I used it.

Yes,you'll see an increase in mileage running in 2hi vs the auto setting.

The fewer moving parts, the better. If it doesn't move, it doesn't wear out and it doesn't use energy moving it.

Mine mirrors your numbers...except my truck is Silver
Run mine the same way.

Great question. I have a 2007 Silverado and run it in auto all the time. Guess I didn't even think that it could be causing unecessary wear and tear.

I had a 2003 4X4 GMC 1500 that had the auto feature. What short time I owned it I never used that feature. When the going gets tough (roads slick, rough terrain) I generally have a good idea as to when I need to put the truck into 4 hi. I could see where the auto feature would be great if the wife was driving in bad weather. Some women may not know exactly when to put a vehicle into 4 wheel drive. Hence, all of the SUV's and stuff that have 4 wheel drive that kicks in when a wheel slips. Modern technology at its best.

The auto feature is very useful for patchy ice or broken snow. It also enables a driver to get waaaay overconfident.

My Silverado normally stays in 2Hi. Sometimes use "auto" on slick roads/dry roads combination, when applicable. Lots of hills in these parts, works fine in those conditions. Primarily on two lanes, although have punched it on snow covered 4 lanes, a time or two.

Drove 4x4s back when manual hubs were the norm. Much prefer today's systems for on-road driving in bad weather.

I have the 5.3 4spd OD trailer towing package (axle ratio ?) and I get about 18 highway. The auto function is nice for mixed patch ice & boat ramps, but it looks like I'm going to switch to 2 hi now. We live in the city and avoid using the pickup since its hard on gas, clumsy in traffic & parking, and why wear out your truck when you can wear out the wifes cheaper car!

I always assume the t-case was running continuous and the auto lock was on the hubs after sensing wheel slip and 4 wheel function electrically locked the hub and what ever shaft was asked for.

I had an '08 GMC Sierra 5.3L 3.73's that I put 145k on the clock. That truck went through three tough winters, and was basically left in Auto 4x4 each winter. Never had any problems at all with the system. Worked great! Now, I have an '11 GMC Sierra 6.2L with MAX trailering package and 3.73's. So far this winter, we really haven't had much winter yet, so this truck hasn't been used very much in Auto 4x4, but so far it is working flawlessly, just like the other truck. Do love the extra power of the 6.2L!! While I don't concern myself overly much about fuel economy, the difference between the 5.3L and the 6.2L isn't very much, I figure I am losing about 1 mpg gallon driving the 6.2L. Well worth it to me for the extra horses!

Wife and I have a 2003 and 2007, neither have ever had the 'auto' feature used. If the roads are nice, 2hi. When the roads are bad, 4hi.

Normally fuel economy doesn't bother me, but 2 mpg saves me $10 per hunting / family vists up north. I never thought about it until I a guy at a gas station with 09 chevy told me he can get 23 mpg if he takes it easy on the gas. I have a topper on mine so I don't know if that hurts it or not.

All I remember is I thought I found a pot of money When I sold my 13 mpg ford truck and got this chevy!

Sadly... nothing saved me as much fuel hunting trip money as when I used to drive my little car up north for grouse hunting and it saved $250 a fall over my 83 chev pickup I had then!

I've got the auto feature on an 06. I like if for driving around town, come bad winter weather the roads in Havre are schit. I don't like driving in 4wd when making turns and the front tires grabbing patches of dry pavement, and I don't like going back and forth between 2hi and 4hi. I'm glad it has it and I like it for the wife's sake too.

I would use mine only when driving on patchy roads. All snow =4x4. I have also heard it called the wife button. If my wife calls and the roads are bad, I tell her to put it into auto.

The auto 4wd feature takes advantage of technology that is already on the vehicle to give you instant 4wd, namely the wheel speed sensors used by the vehicle's anti-lock brake system.

When you select auto 4wd, you're engaging the vehicle's front hubs, but not engaging the transfer case that actually sends power to the front wheels. If the vehicle computer system detects rear wheel slip, the pcm or power-train control module will send a signal to activate the transfer case sending power to all four wheels.

Use auto 4wd in situations where you might experience intermittent loss of traction, such as blowing snow, patchy ice or even heavy rain.

As for the downsides of running in auto 4wd, well you'll have both your front half shafts turning all the time. It's up to you if that's a concern. For me I'd use the auto 4wd feature if I suspect I might encounter a low traction situation as I've already discussed. If you're on really slippery surfaces such as snow covered roads, my preference would be to engage 4wd high for continuous power deliver to all four wheels - actually power to two wheels unless you have locking front and rear differentials but that's another topic.

Hope this helps.

reading this I find it kind of funny i don't have an "auto option" just a lever on the floor, and if i need 4wd it seems i'm always in 4 low, but i learned to drive in a 2wd pickup and jsut don't like the idea of reduced mileage even on ice, but saying this i probably jinxed my self

This was very helpful. Thanks Walt.

My 99 Silverado Z71 had a new transfer case at about 150K miles. I used the auto feature all the time (winter in AK) I knew It was going because I could hear the chain slapping the case.

On the other hand, my wife's 03 Trailblazer has the same feature. It stays in auto all winter, currently has about 140K miles on it and the transfer case is as tight as it ever was.

I have an 04 Chev 1500 Z71 with 265000 miles and just replaced the transmission for the first time. Usually run in 2 hi except when road conditions are variable and then in auto mode. Mileage is about 18-19 overall with not much observed difference except when I go to 4Hi which drops mileage significantly .

I have the 5.3 L Fle Fuel engine on my 2011 Z71 Silverado and I get nowhere near that kind of mileage, especially in winter!

Aroound town and short highway i would say I average 15 to 15.4 mpg.

I had an 05 z71 crew 5.3L non FFV and only got 15-16 or so in mixed driving.