Been some time since I posted so hi everyone!

A few weeks back I got a black on black 2011 Silverado LTZ EXT cab with the 5.3 @33k miles. 18" chrome wheels. Stock everything. This truck was seriously like brand new. The hitch was never used..I assume it never towed. There isn't even a scratch on the thing!

Coming from a 2001 WT it has been quite nice. Only thing that really sucks is that Bose stereo which was a major downgrade from my custom install but that will be fixed soon enough.

Onto my questions.

Is it normal for the oil pressure to fluctuate between 37-38/44-50?

I think the alternator might be going bad. Sometimes when you drive it is 12.5V like the truck is running off the battery. The voltage never drops really low though. After some time it will kick back up into that 14+ area. Is this a form of voltage regulation or is there something wrong?

What kinda MPG should I get? Around town I get 16ish and on the highway I got 17.4. I really really thought I was going to get better MPG from this. My 2001 4.8 with 280K miles did better...

Lastly...the truck IS still under warranty but it would be nice to tune. Are there any decent MPG gains to be had there? The truck was bought 99% for work and less for play so HP probably won't be the goal of this....yet.

 

There is a large difference between the oil pressure that you'll see between a gen 3 motor and a gen 4 motor. Gen 4's have a relief valve in the pan, the DOD lifter require less oil pressure or GM wants them to see less oil pressure.

Cold starts will still be 50-60+, but once warmed up it's normally between 35-45ish going by the dash. Will rise some if you stomp on it. Gen 3 motors always seem to be 50-60 on the freeway and see 70+ at WOT, then 40 or so at idle.

The voltage stuff you talked about sounds normal to me too, my truck does the same thing. Drops down to near 13v and will rise to 15ish volts at random, has like a built in regulator.

MPG can vary alot, 10-13 around town is what I get with my short trips all the time but that was this winter. I'm sure with wamer temps this summer I can get 13-15 maybe in the city. On the freeway I have seen 21-22 with the DoD active, I tuned it out and see 19-20 everytime I'm on the freeway with the instant economy info up.

I havent done a full tank of just straight freeway yet but will be in a few months for a road trip, I'd say if I got 18-20 on avg for the whole it would be pretty good with no DoD.

Also I don't really ever drive above 70, 65-68 is kinda my zone when I'm in no hurry.

 

Sounds great to me. I just wanted to ask cause all I really have experience with is gen 3 engines. My 4.8 runs 50-60 almost all the time. I've been driving these since I was like 16 so yea. This is my first real experience with a gen 4 engine. :p

I also guess that is just the MPG this gets. Hey, least it has heated seats and electric windows. I think that is worth a little trade off lol.

 

MPG could depend on gear ratio too. I have 3.42's so it does a little better on the freeway.

 

The voltage movement is normal, every gas GMT900 I've ever been in does the same thing.

 

My 07 varies in voltage but it is fully normal.
GMT900 trucks and more newer model vehicles actively monitor the battery and there's a voltage/current sensor on the pos. cable that tells the computer some stats. if i remember right, theres an algorithm that is used to drastically reduce battery wear. When the voltmeter on dash goes below normal 14-15v range, the regulator shuts charging power off from the battery enough to where the battery has to work and drain itself some in order to make room for a recharge. Think of it like a trickle charger.

either way, it scared me at once too when i got my truck so i tested it and she does just fine. These alternators are beasts and under rated. They have been tested to pump out almost 200 amps at idle rpm (heavy load occuring at idle causes reg. to respond).

My 07 NNBS gets far worse mileage and i have more miles. its always been a lil piggy with fuel but eh. its a truck. moving a large brick shaped object through air is going to take some fuel. Im impressed the stock truck gets that mpg.