GM 5.3 gas mileage

[deerefan]

'03 Silverado Z-71 Ext. Cab. A/T tires, tool boxes in bed full of "stuff". 5.3 engine, about 80K miles. 3.73 gears.

Normally I avg. about 15-16 mpg. Normal highway driving about 17-18. Recently I followed my buddy who was towing a camper and we kept our speeds about 60-65 in the interestate instead of the normal 70-75. I avg. 19 mpg on the way up. On the way back I was solo and got about 17 mpg but I was going about 70-75 mph.

Also take into consideration the trucks of today are probably much heavier. Also I would bet that even though they have 6 speed transmissions the final gear ratio is probably not that far off from my 4-speed.

I am starting to think you are right on with the ratios in the 6 speed and 4 speed. I just have a hunch something is amiss. I am making it a point on this tank of gas to keep speeds around 60 or less and see what happens.

 

[LD1]

I am starting to think you are right on with the ratios in the 6 speed and 4 speed. I just have a hunch something is amiss. I am making it a point on this tank of gas to keep speeds around 60 or less and see what happens.

Correct. The final drives arent much different. And the first gear ratios arent much different either.

BUT the 4 speed only has 2 gears inbetween, and the 6 speed has 4.

This is a HUGE benefit when towing. You dont have to crank the rpms way up before a shift. The RPM drop between shifts is MUCH less.

It also helps out fuel economy better, because it keeps the RPM's where the motor makes best torque and fuel economy easier.

And I dont know about them being any heavier. I think they are probabally about the same. These newer ones have more saftey and emissions and power ammenities, but the older ones IMO used heavier body components and solid front axles with leaf springs, etc.

And have you ever weighted one of them old 203 or 205 t-cases compared to these newer aluminum ones that dont weight but ~40-50lbs?

I had a 1985 dodge 3500. It was more like a 2500. Only an 8600gvwr and srw.

Just an old work truck, no power features or extended cab. 6100lbs on the scales.

My 03 chevy I had was a 1/2 ton, but was extended cab, power everything, leather, toolbox in back, and plow brackets/pump off front, and it only weighed 5800lbs.

I could be wrong, but I'd venture to guess that a NON diesel moder 3/4 ton to SRW 1ton std cab long bed 4x4 doesnt weight any more than the 6000lb or so ones from the 1980's

 

[k0ua]

my 2000 yukon, with 5.3, and I believe 3.73 rear and auto trans gets about 14mpg, and only uses about 2qts of engine oil per 3000 miles... since new.. and gm says that's normal

no leaks either..

soundguy

My 2000 Silverado 5.3.. (before it got wrecked in 2010) used no oil, my new silverado replacement with 5.3 uses no oil either.
James K0UA

 

[LD1]

My 2000 Silverado 5.3.. (before it got wrecked in 2010) used no oil, my new silverado replacement with 5.3 uses no oil either.
James K0UA

My 2003 5.3 that I just traded in had 104000 miles on it. I did oil changes @ 7000mile intervals. At that 7000mile point, it was maybe 1/2 low at most. So, I pretty much call tht using no oil either:thumbsup:

 

[Kernopelli]

I just purchased a 2000 silverado extended cab Z71 w/ 68,000 miles. 5.3 w/ 3.73 gears. I have not done any hand calculations yet but highway mileage appears to be at least 18-20mpg and not sure that it's not slightly better, this is at 60-65 MPH. City seems to probably be half that.....very disappointing. This is really babying it too. I am starting to wonder if it's not best to just hammer it and get up to speed then let off and cruise at posted speed limit as opposed to dogging it up to speed? Any opinions on how to get the best mileage around town?

 

[The Haymaker]

I bought a 2011 Z71 4x4 ext cab in December. It has the tow package and 3.42 gears with the 6 spd auto. I have about 5500 miles on it and am averaging 15.8 mpg hand calculated. I find this rather disappointing considering my 97 F150 4x4 ext cab with the 4.6, 4 spd auto and 3.55 gears get 15 flat. Here we are 14 years later and light years ahead in technology and the mileage is basically the same. I can't call GM a liar as it states 15-21 mpg on the sticker and I am getting 15.8 (the computer mpg says 16.3 avg). For comparison, my father has a 2010 avalanche, 2wd 3.42 gears and he is seeing 18-19 mpg. I drive normally, not lead footed. Another thing I noticed is at 62 mph, I am turning the same rpm as my ford. Weird considering my trans has 2 more gears than the ford. Anyone have the same truck? What mpg are you getting?

Consider yourself lucky. My 2004 5.3 has never even hit 15 and because of GM's response, it may be the very last GM (all I've ever had) I own. It was 13 when I drove it off the lot. The GM customer service (service, bahaha!!!) rep said "Wow, you should be better than that" so she had it put on a computer. Nothing found. I called her back up and got a response of "The scan found nothing wrong, what do you want from us Mr. Foster". This was the SAME woman.

They then said it was the way I drove, even though it does the same at 65 with the cruise on as it does 85. They then moved on to "tires". I swapped in my new BFG 31" TA's when I bought it. Great excuse, except going up two sizes in tires has always increased highway mpg for me.... Oh, and the fact that if the truck had Z71 stickers, it'd have the same size tire. There is no difference in gearing, tranny, or programming. That said from an engineer in Detroit that I break bones with. But then, this was the same shop that said they wouldn't cover any brake defects because the 31" tires would destroy the ABS. He tried to tell me that the axle sensors were matched to a ground speed sensor so the system would know. Umm......

And then there's the front wheel bearing that failed at 37k miles, 1k outside warranty, and even though the local dealership was replacing upwards of 15 a week at even lower mileages, GM said "Tough Sheet". Again, GM friend said "We saved a penny piece on those cheap units and we're still paying for them."

We shoulda let them fail.

 

[timswi]

Haymaker...My 2004 GMC 5.3 was trouble free except for the dash cluster that GM replaced ouside of warranty..

Sounds like bad luck to me. You have my sympathies. The dealer has some input as to whether to replace something outside of waranty, especially if it's one of those "shouldn't have happened" things. The regional guy holds the most sway on these things generally and the dealer can have a conversation with him on your behalf, that's their call though.

 

[timswi]

Haymaker...My 2004 GMC 5.3 was trouble free except for the dash cluster that GM replaced ouside of warranty..Traded it in at 100K, no leaks and the truck still looked and ran like new and was nearly original in terms of hard parts.

Sounds like bad luck to me. You have my sympathies. The dealer has some input as to whether to replace something outside of waranty, especially if it's one of those "shouldn't have happened" things. The regional guy holds the most sway on these things generally and the dealer can have a conversation with him on your behalf, that's their call though.

 

[deerefan]

I will say this, out of all my half tons, it pulls the best. I brought my 3 horse sundowner trailer (about 3800 lbs) to get a tire repaired to town this morning and it pulled it great. Not much weight but a bit of a brick with the wind. Very little downshifting and no gear hunting like my 05 Z71. This is my 6th half ton, 4th GM 1/2 ton. The other two were F150s.

 

[Don87]

98 Dodge Dakota, Magnum V6, 5 speed manual.........12mpg on a good day.
8mpg if I put a load of coal in it, or pull a 4x6 trailer with a 4 wheeler on it.