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See the above gas mileage chart for my Silverado (I save all my gas reciepts). Have 10K miles on it. I'm retired and don't drive it much. You can tell when I take highway trips. Always have the tranny in "D" range when driving except when in lots of hills (rarely) then I put it in "3" range. This is a regular cab short bed truck.

Seems it should be getting better gas mileage. I have noticed that it seem like the transmission is slipping some. When I slow down then accelerate, it will jerk a little. Same when accelerating from a stop. Chevy dealer won't do anything.

How difficult is it to adjust the trans?

Spot anything else from the chart data? Seems like MPG is going down instead of up like you'd expect.

 

The Graph to me seems to very widely between 10mpg and 20mpg. Back in 07 I had a similar graph chart that did not very in MPG as much. Does not sound like you are towing which would explain some of the jump mpg. Is the truck New body style or classic? As for the jerk, maybe the yolk needs to be greased? my 06 had the thump in the rear and some times would feel like it would catch/jerk. Just greased the yolk and been running for a few thousand miles with no issue now. As for modifying transmissions it is mostly done by hand held programmers which run $300 and up or getting the computer reprogrammed.

 

Well with my 04 I had the same problem wiht the MPGs varying from 20 to 16 on Highway trips. With that being said the motor is not even broken in. After I got 15 or 20K on it it then started to settle down. Then I started moding it and it increased a bit. However if the dealership will not do anyhting about it then take it to another dealership then another... better yet let the tranny start to leak fluid run it dry and then tell them to come and get it or drive it in in 1st gear at a high rate of speed and come to screeching halt in front of God and everyone and get out and walk in really ticked off asking for the store owner!

 

I would pay to see that!!! If you watch MythBusters you would know what happens when you try and throw it in Reverse from Drive at full throttle. (Nothing happens on newer vehicles(standard and auto).

 

I bet it would with a dry transmission if not something would give in 1st gear at a highrate of speed.

 

Ohh yes, I have another idea, just put a fragmentation granade in the oil pan of the tranny, pull the pin through the oil drain plug. No, I think that would mess up a perfectly good truck. Just do what Timber said. Drive her till she blows! Just help her there.

 

Whether or not it is a classic or new body style Chevy dealerships have tricked alot of people in buying a lower price truck with a V6 saying it gets better milage than the V8's. I think it is a stunt they have planned to sell more trucks. The 5.3 is the best overall motor now in the trucks. To me I have never seen the point in putting a V6 in a full size truck. I would just put 5.3's or 6.0's and drop the 4.3 V6 and the 4.8 V8 and save the company millions of dollars.

 

Gpet6669 must be a former military guy like I am... "Fragmentation gernade" YEAH!
I also had to add a quart and a half to my tranny that the dealership could not find a reason for for the missing fluid... no leaks just magically disappeared. However after I B!@#$^& enough the dealership finally did reprogram my Computer for the transmission shifting problem.
Oh yeah when on a road trip vary your speed so the engine will help seat the rings. And don't drive 80 plus on a road trip until after atleast 45K.

 

I am actually still in the Military, however I am on my way out. (Med Ret.) Hopefully not before I get my back surgery done.

Back to the subject. I think your overall fuel consumption issues are a bunch of different factors adding up. One, the drivetrain set-up, too small of an engine for the weight it has to push down the road. Two, the tranny is probably not shifting when it should be for this motor and vehicle weight combo. It could be fixed if the tranny's computer was reprogrammed, just like Timber was talking about. Three, we all know that there is more fuel efficiency and power after the vehicle is properly broke in. Therfore, the motor isn't at full effiecency yet.

But if you put a CAI, cat back exhuast on, and have the vehicle reprogrammed with fuel economy in mind, (Motor and trans optimized to each other) then it would more than likely do a lot better than stock ever could.

Did I miss anything??

 

Also the graph does nothing unless you split when you are towing a certain amount in one group, highway traveling in another, and city only driving in the last group. Having them all together cannot tell anybody anything unless that is what the truck does in basically the same conditions all the time.

Like me, I just drive my truck to work, so that is when I measure my fuel consumption. If I go on a long trip or haul something I skip that tank and go to the next one. That is the only way to be able to diagnose something that may be wrong with your truck by watching fuel consumption.