Real World 2010 5.3 With 3.08 Axle Mpg?

b00001 · April 29, 2010

Would like to hear from owners with the 3.08 Axle, preferably with the 18'' or 17'' wheels, as to what kind of MPG they are getting.

HWY #'s are most important to me. Real calculated #'s please, no "abouts" (i.e. about 20mpg, about 21 mpg, etc).

Thanks!

rogersinsel · April 29, 2010

Would like to hear from owners with the 3.08 Axle, preferably with the 18'' or 17'' wheels, as to what kind of MPG they are getting.

HWY #'s are most important to me. Real calculated #'s please, no "abouts" (i.e. about 20mpg, about 21 mpg, etc).

Thanks!

I have an '09 Tahoe LTZ with factory 20" wheels. In highway only I achieve anywhere from 18-19 MPG. However, that is driving at or inexcess of 70 MPH. I do know that if I stay at or below 65 I an easily crest 20. If you drive it right your combine numbers will be around 17-19 and that is not bad considering the size of this SUV. I looked at the Acadia because of its supposed better MPG numbers, but if you ask most of them they'll tell that they never get sticker. So I bought the larger Tahoe instead. If you are afraid of the gas, then go with the GMC Terrain, it gets excellent numbers.

Zembonez · April 29, 2010

WOW. 3.08 axles are still available? What a slug that will be. Real world 3.23 numbers are about 16 MPG mixed driving.

rogersinsel · April 29, 2010

WOW. 3.08 axles are still available? What a slug that will be. Real world 3.23 numbers are about 16 MPG mixed driving.

There is not a 3.23 available with the 5.3, only the 4.8 and I do imagine it needs it. The 5.3 comes with either a 3.08 or a 3.42 and in the standard config only nets a 500 lb increase. 5400 vs. 5900 lbs. 8400 lbs. with the kl5 option. The 5.3 with the 6 speed and the 3.08 will get with it. It loves those gears when you use them and when you back off returns good MPG.

caddycruiser · May 1, 2010

WOW. 3.08 axles are still available? What a slug that will be. Real world 3.23 numbers are about 16 MPG mixed driving.

There is not a 3.23 available with the 5.3, only the 4.8 and I do imagine it needs it. The 5.3 comes with either a 3.08 or a 3.42 and in the standard config only nets a 500 lb increase. 5400 vs. 5900 lbs. 8400 lbs. with the kl5 option. The 5.3 with the 6 speed and the 3.08 will get with it. It loves those gears when you use them and when you back off returns good MPG.

Agreed. A 3.08 rear WOULD be a slug with the old 4-speed gearing, but is the polar opposite when combined with the 6-speed. Different animal. Won't win stump pulling competitions, but moves well and I continue to be fascinated with how low/dead RPM's mine will steadily cruise at. Barely over 1000 on the road, just idling along.

So far my '09 Avalanche 2wd Z71 with the 18" wheels and 5.3L/6-spd/3.08 rear is getting around 17mpg in daily driving stop & go and can go 20-21 on the highway, depending on speeds. In my daily driving, it actually gets better mileage in a lot of ways than my 6.0L G8 GT did before. Not nearly the same power, but still a very peppy/silent/smooth truck.

And interesting thing as of late (today) came with changing the tires. Originally, it had the rather luggy 18" Bridgestone Dueler A/T RH-S treads on Z71 & other 18" wheel models, from the factory. Got the mileage above. Today I swapped those out for new Michelin LTX M/S2 treads and from the first drive, since I always have the Instant MPG screen on, already scoring higher numbers in exactly the same conditions. Just seems to roll more easily with stiffer, smoother tread, and even gets in/stays in V4 mode a little more. Great additional upgrade to come with new treads, and I can feel the difference.

My average #'s are in the MPGTune.com link in my signature, as well.

mikepike1125 · May 31, 2010

I have the 5.3 v8 with 3.08 and I am getting 15.5 mpgs around town. I cant help you out with highway miles since I havent really taken any long trips with it yet. If I do I will let you know what I am getting.

Stevens03 · May 31, 2010

Man, I'm sorry, but that's horrible mileage... My 6.0 4-speed with 4.10 gears gets almost the same mileage. I get 13-14 depending on driving habits and 17-18 highway. Sorry to break it to you, but those 3.08 aren't enough gear with the 6-speed or not to get good mileage... the truck is just as heavy with the 4-speed or 6-speed.

Maybe on a flat drive down the highway at 55 you'd be alright.

kalashluvr · June 1, 2010

Would like to hear from owners with the 3.08 Axle, preferably with the 18'' or 17'' wheels, as to what kind of MPG they are getting.

HWY #'s are most important to me. Real calculated #'s please, no "abouts" (i.e. about 20mpg, about 21 mpg, etc).

Thanks!

As long as the overall tire diameter is the same, you will get the same mileage with 17's, 18's, or 20's....Just filled up the tank on my brand new 2010 Silverado with 3:08 axle, 6-speed and 20 inch wheels, and went 405 miles on 22.634 gallons of fuel, for an overall MPG of 17.89. I use the DIC for backup numbers to compare....I use the pump and calculator to figure out the numbers. My commute is 50 miles round trip per day, with about 15 traffic lights as possible stopping points. I think I probably hit 5-6 of them going one way, and have one "mountain" to pull each way, so that means I get to coast for a few miles one way also. I would say that my "highway" mileage is 70% of the tank of fuel. My tire pressure was 35 in right front, 37 left front, 37 right rear, and 35 right rear. I evened them out to 38 psi in the front and 39 psi in the rear. I drive pretty conservatively off of the line, and I don't get over 65 mph, trying to stay around 55-60 mph, and when I see a traffic light turn red up in the distance, I left off the pedal and coast, trying to time the light so it turns before I come to a stop. I'm hoping I can get my overall mpg with the same commute up to about 18.5 when the engine gets "broke in". It will be 4-5 days before I fill up again and the conditions will be very close to the same (with slight improvement!!). I feel like I definitley had to "milk" it to get the 17.89 MPG, but that's the way I do all of my vehicles (except my 1976 F-100, which I just drive with no regard to mpg because the headers and flowmasters just sound waaaay too good.).

kalashluvr · June 1, 2010

Would like to hear from owners with the 3.08 Axle, preferably with the 18'' or 17'' wheels, as to what kind of MPG they are getting.

HWY #'s are most important to me. Real calculated #'s please, no "abouts" (i.e. about 20mpg, about 21 mpg, etc).

Thanks!

What MPG are you getting now (and how many miles are on the truck)? Also, what kind of tires are you running? I test drove a Silverado with the 17 inch all terrain tires that typically come on the Z-71's, and it definitley felt like it took a little more to get it going and I don't even remember it kicking to 4 cylinders.....the 20's are street tread and it feels like it gets rolling much quicker with the same "input" from the gas pedal.....just my .02...

mikepike1125 · June 1, 2010

ok I just went down the mass pike (highway) to pick up my girlfriend at the airport. I traveled 12.5 miles while using .5 gallons of gas. So that would be 25 mpg. Please note that I do not have my stock 265 70 R17 tires on. I have a 275 55 R20 tire on right now. They are almost the same diameter but not quite. With these 20's on the truck I am travelling at 60.6 mph while the speedometer thinks I am going 60 mph. So my speedometer is reading about 1% too slow with the non stock tire I have on now. I get 638 revolutions per mile with the stock tire vs. 632 with the non stock 20". So for every 60 miles I travel according to the truck I am actually traveling 60.6 so I guess you could say that I am averaging a bit better than 25 MPG's on the highway.

Anyways, the main factor in achieving good mileage with this setup (5.3 v8 3.08) is maintaining an average speed of 55-65 mph. I think you will see your best highway MPG if you can stay within this range.

I am driving 2010 gmc sierra 1500 extended cab 5.3l v8 6 speed auto 3:08 ratio 4x4

highway was fairly flat

RCP · June 2, 2010

I drive an Xfe model and on a recent road trip with the bed full of camping gear and a hitch mounted cargo carrier loaded with 2 big coolers full of food, beer, and ice I managed almost 23mpg. I maintained an average of about 70-75mph most of the way.

kalashluvr · June 3, 2010

ok I just went down the mass pike (highway) to pick up my girlfriend at the airport. I traveled 12.5 miles while using .5 gallons of gas. So that would be 25 mpg. Please note that I do not have my stock 265 70 R17 tires on. I have a 275 55 R20 tire on right now. They are almost the same diameter but not quite. With these 20's on the truck I am travelling at 60.6 mph while the speedometer thinks I am going 60 mph. So my speedometer is reading about 1% too slow with the non stock tire I have on now. I get 638 revolutions per mile with the stock tire vs. 632 with the non stock 20". So for every 60 miles I travel according to the truck I am actually traveling 60.6 so I guess you could say that I am averaging a bit better than 25 MPG's on the highway.

Anyways, the main factor in achieving good mileage with this setup (5.3 v8 3.08) is maintaining an average speed of 55-65 mph. I think you will see your best highway MPG if you can stay within this range.

I am driving 2010 gmc sierra 1500 extended cab 5.3l v8 6 speed auto 3:08 ratio 4x4

highway was fairly flat

I think that flat roads have ALOT of influence on the mileage on these trucks, especially if you aren't coasting after pulling a hill and going down the other side (if there is another side).

I drove 70 miles on the interstate and highway today, and experimented with the mpg readings on my DIC display. I ran it at 80 mph for a minute on level highway....DIC showed about 18 mpg. Dropped down to 75....instant mpg came up to 20-21....dropped down to 70...not much difference. Then I dropped down to 60-65 and the mileage would bounce between 22-23. When pulling a slight incline around 65 mph, the instant mpg would drop to around 16 mpg if I remember correctly.

b00001 · June 5, 2010

Update: 2010 Silverado Ext cab, 3.08 Axle, 18'' wheels. Mostly hwy at 70-75 mph. 2nd full tank of gas yielded 18.6 MPG, 3rd full tank yielded 20.05. Just over 1000 miles on it. I expect the mileage to improve as the engine logs more miles. Quite pleased so far.

This truck was a bit of an experiment as I came from a 2009 Silverado, crew cab, with 20's. The 20's WILL decrease your mileage.

kalashluvr · June 6, 2010

Update: 2010 Silverado Ext cab, 3.08 Axle, 18'' wheels. Mostly hwy at 70-75 mph. 2nd full tank of gas yielded 18.6 MPG, 3rd full tank yielded 20.05. Just over 1000 miles on it. I expect the mileage to improve as the engine logs more miles. Quite pleased so far.

This truck was a bit of an experiment as I came from a 2009 Silverado, crew cab, with 20's. The 20's WILL decrease your mileage.

You say the 20's will decrease your mpg...how so? Are the tires not as "low resistance" as the 18's or are they just heavier and take a little more juice?

b00001 · June 6, 2010

Update: 2010 Silverado Ext cab, 3.08 Axle, 18'' wheels. Mostly hwy at 70-75 mph. 2nd full tank of gas yielded 18.6 MPG, 3rd full tank yielded 20.05. Just over 1000 miles on it. I expect the mileage to improve as the engine logs more miles. Quite pleased so far.

This truck was a bit of an experiment as I came from a 2009 Silverado, crew cab, with 20's. The 20's WILL decrease your mileage.

You say the 20's will decrease your mpg...how so? Are the tires not as "low resistance" as the 18's or are they just heavier and take a little more juice?

Not only are the 20" tires heavier than 18, but the rim is significantly heavier as well. Takes more juice to get them going and keep them rolling. I have the more aggressive Bridgestones (18'') on my current truck and still getting much better mileage than the 20's I had on the '09.