Anybody out there with the 4.8L and 4-speed knows its never going to win any mileage awards. Mine has been averaging 15.3 mpg in my normal driving. This last week, I tried hypermiling. I slowed to 60 (the posted speed limit) on my commute instead of my normal 69, pretty much went the the speed limit or less everywhere, coasted whenever possible, even cut the engine at lights I knew were long. No ac (not hard, its been cool all week) or warming up the truck.

Result; 16.6 mpg

At $2 a gallon, I would only save $2.60 on a tank. Considering the effort that it took to achieve that, I would have to say hypermiling is pretty much worthless in my truck!

Maybe its just me, but most mileage improvement techniques are garbage. Never worth the cost/effort. Smaller motors and/or more gears seem to be the best bet.

 

Yeah I'll agree.

I usually drive 77-80 but I have a 5.3 AFM and a 6speed.

Fuel economy is a pretty consistent 21.5, but if I turn off the cruise control and just use my foot to avoid accelerating up hills, I've stretched her to 24.7 for a tank at that speed.

I haven't tried lower speeds... why would I?

 

My '04 with the 5.3 and 3.73 gears gets pretty consistent 12.6 mpgs ... lol took a 600 mile trip a week or two ago. Still got 14.5 on the expressway going a consistent 75mph. Oh well, it tows my boat nicely, that's all I care lol

 

Over 45 mph, fuel economy goes down. If you could drive 45 mph everywhere, you would save fuel. However, like most people, I commute partially on a 4 lane highway with a 60 mph speed limit where driving 45 is nearly as dangerous as driving 80.

I tend to agree NullHead. I knew going in I wouldn't be able to afford the latest technology. I have a Mercury Grand Marquis in the driveway that gets a consistant 21 mpg. But I can't go to home depot or tool around the farm in a sedan.

 

How odd...

I have a 2000 4.8 with an auto, presently showing 260K miles on the odometer, and it will pull 20 MPG all day long on the interstate. On a recent trip from Macon Ga. to Wayne N.J. ( about 1000 miles) I cruised most off the trip at about 75 mph, and my log book shows 20.6 mpg's on average for the trip!

On another trip from Georgia to New Mexico, I averaged 20.25 mpg. I'm pretty sure the mountains took some out of the MPG's on that trip.

Life time average on my '08 5.3L is 16.6 mpg's. . That includes towing a trailer, either full of car, or equipment for a good number of the 140K miles on it.

The way you drive also has a lot to do with your MPG. I remember reading an article in one of the car mages, and it stated that more the 60% of manual trans drivers get worse MPG driving a stick, than an automatic. They stated a number of reasons, but the main reason is that most people either don't know how, or are not comfortable driving a manual trans vehicle ECONOMICALLY. Most people drive manual shift vehicles, like their name is "speed Racer".
While everyone I know who drives a manual shift vehicle has denied that, I see them doing it while they are driving. It's almost a natural thing to wind out each gear as though you really needed to. lol

Now, I'm not saying that that is your problem, I'm just quoting the magazine that claims "more than 60% of stick drivers do it, knowingly, or unknowingly".

 

This is my normal combined driving, I can do better on the interstate in flat territory. There are other factors. First, my truck is absolutely the heaviest combination available with this engine/tranny in 2012. And even though its an SL, they didn't skimp on the options, so even more weight. The original tires were thin when I bought it and worn out by winter. In December I made the conscious decision to skip on mileage biased highway tires in favor of all-terrain tires. My driving style these days is middle of the road. I was a real lead foot in my youth, and like I said above, driving for mileage drove me crazy. I'll pass and maintain speed uphill, but I don't jack rabbit away from every light any more or pass just because the person in front of me is goin 1/2 mph less than I want to drive. Also, my truck is a TRUCK. I carry tools, tow strap, hitches and hooks, all the stuff I need to do truck stuff. One of the things I like about my truck is opening the truck box and pulling out whatever I need when I need it. So yeah, my mileage sucks, but I guess it just will for a while, because I am not ready to trade the versatility of Old Jim for 30 mpg.

 

lol....

I have 2 Trucks, that I use for work. I'm a small business owner. We build and install custom personnel doors.I use them both as trucks, too.
As I told you, the 2000 Silverado is a 4.8/auto. It's a regular cab long bed. with a tool box. I usually use it to carry the doors because of the 8' bed, but the tool box is full of the tools and supplies we use for installations. The second truck is a 2008 Sierra Crew cab, with a short bed. It has 3 tool boxes on it, and we also use it to transport the work crew, and it's also set up to pull a 16' box trailer, usually filled with hardware and supplies, and some times doors ( on rainy days.

I've noticed that my 4.8L truck can do nearly 2mpg better when the tool box is empty, verses when it full. My best guess is that besides the weight of the aluminum tool box, itself ( which never comes off the truck) the tools probably weigh in at about 300-325 pounds. So, it's pretty apparent that the weight ( equal to 2 passengers) will cost about about 2 MPG's. Based on that, every 150-160 lbs you're carrying round on a regular basis is costing you about 1 MPG.

That's only a theory based on my observations of my trucks performance, but it's a theory you could probably verify over a week end. It won't change the mpg's you're getting, but it might answer your question as to why your MPG's are lower than you'd expect.

btw, I'm not a member of the 30 MPG club either. Besides the two truck I mentioned, above, we also have a 2015 Suburban LTZ with a 6.0L in it. It's not mileage queen, but, my wife likes it FAR better than the Toyota SUV she used to have. lol

 

Oh my wife loves her Jeep Patriot, but I HATE it, and not just because its a pain in the butt to work on. I call it the "Tin Can" because that's what it feels like inside. My big 6'3" frame needs some room.

 

Agreed...

We got the Cruze diesel because we figured we would drive it on long trips to save money as the fuel economy is INSANE...

But half the time I just bite the bullet anyways because I don't like feeling every bump while having my knees by my ears

 

I got in a Cruze on a lot. Set the seat, then got out, the seat was actually touching the back seat.