[jdelrizzle]

I have a 5.3L, 2wd, sle. All 5.3s with the Texas edition package are marked as 14/19, but the GM website and other non Texas edition 2wd sierras/silverados on dealer lots are rated as 15/21 mpg's. What gives? Is it the 20 inch rims that bring down the mpg rating?

 

[JSDelaware]

I'm betting this is just an inaccuracy on the dealer's website.
GM doesn't have to rate every possible combination of equipment for each motor,
although, if they did do separate tests for vehicles with 20's, it probably would bring down mileage.
I have seen plenty of these trucks with the 5.3 and factory 20's and actual window sticker on all the trucks
I have seen said 15 21...... but not to worry you won't get that mileage anyway.

Joe

 

[yergerjr93]

I don't know how they came up with 21 or 20 mpgs... I get the biggest grin on my face when its reading 17 mpgs. I feel like I can brag to the pruis owners how I can look good and also get great mileage

 

[jdelrizzle]

Joe, hahaha, very true, I average 16 mpg…

 

[wildchevy]

I don't know what you guys are doing but I average 21-23 MPG on my freeway commutes to work every day.

 

[yergerjr93]

what kind of speeds are doing for your commutes? I go usually 55 mph on the freeway, but then I go 80 mph on the highway. and mines usally comes out to 17. something, which isn't bad at all in my opinion.

 

[TooTall999]

Rim size won't bring down MPG. A 17" rim and a 22" rim could potentially give the same mpg as long as the overall diameter and weight with the tires is the same.

 

[esox07]

Yep, when looking at trucks last summer, I noticed the stickers on several trucks had the 19 as the highway EPA mileage but most had 21. Mine was 21. Since the truck I was interested in was 21, I didn't ask what the big difference in the trucks were. I would have thought maybe it was 4wd vs 2wd or maybe 5.3L vs 4.8L but I have the Z71 off road package with 4wd and 5.3L so I really don't know. The only other big difference I could imagine would be the rear end ratio.

 

[jdelrizzle]

AHH! Rear end gear ratio! That might be it…

Didn't even think of that.

 

[wildchevy]

what kind of speeds are doing for your commutes? I go usually 55 mph on the freeway, but then I go 80 mph on the highway. and mines usally comes out to 17. something, which isn't bad at all in my opinion.

Most of the trip is 65 and when in Milwaukee it drops to 50 and 55. I hold my speeds at posted limits and use a very light foot with no sudden increases in throttle. 100 miles a day and you learn to squeeze every drop of fuel to the max. I always have more time than gas and money. Between my commute and pleasure driving my monthly fuel bill can be 400-500 dollars and more if I head up north a couple of times a month. When I let my son drive my truck the MPG instantly drops to under 17 MPG so I know it is all in driver technique.

 

[esox07]

what kind of speeds are doing for your commutes? I go usually 55 mph on the freeway, but then I go 80 mph on the highway. and mines usally comes out to 17. something, which isn't bad at all in my opinion.

Most of the trip is 65 and when in Milwaukee it drops to 50 and 55. I hold my speeds at posted limits and use a very light foot with no sudden increases in throttle. 100 miles a day and you learn to squeeze every drop of fuel to the max. I always have more time than gas and money. Between my commute and pleasure driving my monthly fuel bill can be 400-500 dollars and more if I head up north a couple of times a month. When I let my son drive my truck the MPG instantly drops to under 17 MPG so I know it is all in driver technique.

I have a feeling the drop in mileage is those speeds over 60 mph....80mph is going to kill your mileage. It is all about wind resistance with these trucks. They are trucks, not aerodymanic passenger cars. If you have the DIC with the selection for current fuel mileage, then just watch it some time when you are tooling down the highway at 80 mph. Then slow down to 55 and see how much your rated mileage will go up. I did that the other day on the interstate going 72 and then 55 when I was in a construction zone. It was a couple MPG difference. I image the drop in mileage from 72 to 80mph would be a couple more mpg's as the drag coefficient is exponential. Also, I know my truck wont drop in V4 with the AFM when I am traveling much above 60 unless I have a good tail wind or traveling at a down grade so that could have something to do with the drop in mileage after about 55 or 60. These trucks were obviously engineered with a sweet spot of about 55.

 

[Juan Focker]

what kind of speeds are doing for your commutes? I go usually 55 mph on the freeway, but then I go 80 mph on the highway. and mines usally comes out to 17. something, which isn't bad at all in my opinion.

Most of the trip is 65 and when in Milwaukee it drops to 50 and 55. I hold my speeds at posted limits and use a very light foot with no sudden increases in throttle. 100 miles a day and you learn to squeeze every drop of fuel to the max. I always have more time than gas and money. Between my commute and pleasure driving my monthly fuel bill can be 400-500 dollars and more if I head up north a couple of times a month. When I let my son drive my truck the MPG instantly drops to under 17 MPG so I know it is all in driver technique.

I can agree on all that, especially the 55 MPH sweet spot. I regularly take a 450 mile, round trip north and south, on the same stretch of road. In the same 8 hour time span. The first/last 40 miles is rural roads average speed 55. The remainder of the trip is expressway and I usually set the cruise at 79, conditions permitting. That is approx. 1950 RPM's. I get an average of 17+ on an average trip. Usually I can see a 2 MPG variance in the northbound vs. southbound legs of the trip on windy days. On other days, due to rain/snow when I am only able to cruise at 55-60 I can get over 21 MPG. Occasionally, I like the 3.42 gear,lol.

 

[yergerjr93]

I've also notice right around 55 my truck gets real quit and my engine load gauge (on my edge programmer) is reading 20%-35%, on the other hand going 80 its reading 45- 60%.

 

[JSDelaware]

Yep, when looking at trucks last summer, I noticed the stickers on several trucks had the 19 as the highway EPA mileage but most had 21. Mine was 21. Since the truck I was interested in was 21, I didn't ask what the big difference in the trucks were. I would have thought maybe it was 4wd vs 2wd or maybe 5.3L vs 4.8L but I have the Z71 off road package with 4wd and 5.3L so I really don't know. The only other big difference I could imagine would be the rear end ratio.

It's the 4.8s that are rated at 19 highway(2wd) 18 highway 4x4.
All the 5.3s for the last several years have been rated at 15 city 21 highway 2 or 4wd( except for the xfe special editions
which are about 1mpg better)
They don't break out the numbers for the different gear ratios, I'm guessing whichever gearset is standard is the
number you will see on the sticker.
And yes, if you drive 55 with the cruise set all the time,you will likely see the stated mileage.
However most people, no matter how conservatively they drive, do not live in an area where it is possible to do so.
While we are on the mpg topic, my last truck was a 2011 with the 5.3 and 4x4 rated at 15 21. I averaged 15 mpg,
My current truck is a 2012 with the 4.8 and 4x4 rated at 13 18, and I still average 15.
The only difference I can tell is I have a little less power and a lot less cluncking, jerking and shuddering.

Joe

 

[wildchevy]

I never use the cruise and with the Range I don't fell any clunking or shuddering. Next spring when I drop it and add a exhaust I am shooting for 24-25 mpg.

 

[JSDelaware]

I take it from your post that you have the afm turned off?
Did your mileage improve after shutting it off?
I ask because I have read a dozen posts on here from people who have seen their mileage go up
after shutting off afm.
I think it's pretty hilarious that deleting supposedly fuel saving technology seems to improve the mileage on
these trucks.
Seems like the afm is better at manipulating the epa test cycle than actually improving the vehicles mileage.

Joe

 

[CaptainMorgan]

stay around 65/70 and gas mileage is nice. My 4.8, if only interstate driven gets around 22 mpg. Average with 75% around town is 17. But my guess would be the difference in the stickers is the rear end ratio.

 

[jdelrizzle]

Well I'm averaging 15/16 mpg's, that's about 75% city driving, I do however have a light foot, occasionally I will step on it, but not floor it. Dic says im averaging 14.9, onstar says 16, I have yet to hand calculate it, so I'm taking the trucks word for it.

 

[2004lebanshee]

I hand calc mine all the time and its usually reading .6 or so better then it actually gets.

 

[jdelrizzle]

You mean .6 or better than the dic?