01 tahoe 5.3 performance and fuel economy

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Mhurter

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Hey guys! New to the forum, but not new to the gmt800. Had a 2000 Sierra 5 years ago, and it was a good truck but it got fairly rusted so I sold it. After a while I needed another truck so I bought an 01 tahoe 4x4 that was mildly lifted with a hair over 200k. I’ve been taking this truck on road trips over the holidays to ensure that I’ve gotten the kinks out of it, and I noticed that this truck is getting HORRIBLE fuel economy on the highway. At 70-75 I’ve been getting 13mpg! My old Sierra would get 18 easily at that speed. So I’m wondering where I should go to try and improve fuel economy. I’m planning to change all the fluids in the trans, diffs, and tcase with synthetic, but I’m also looking for things I can do to help fuel economy on this thing such as programmers, intakes, exhausts, etc. as a side note, this truck seems significantly down on power from what I remember of my Sierra, no DTC’s set though. Truck is stock besides a stereo and 33” duratracs. Any info y’all have would be appreciated, just tryin to save some $
Thanks in advance!
 

wjburken

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Hey guys! New to the forum, but not new to the gmt800. Had a 2000 Sierra 5 years ago, and it was a good truck but it got fairly rusted so I sold it. After a while I needed another truck so I bought an 01 tahoe 4x4 that was mildly lifted with a hair over 200k. I’ve been taking this truck on road trips over the holidays to ensure that I’ve gotten the kinks out of it, and I noticed that this truck is getting HORRIBLE fuel economy on the highway. At 70-75 I’ve been getting 13mpg! My old Sierra would get 18 easily at that speed. So I’m wondering where I should go to try and improve fuel economy. I’m planning to change all the fluids in the trans, diffs, and tcase with synthetic, but I’m also looking for things I can do to help fuel economy on this thing such as programmers, intakes, exhausts, etc. as a side note, this truck seems significantly down on power from what I remember of my Sierra, no DTC’s set though. Truck is stock besides a stereo and 33” duratracs. Any info y’all have would be appreciated, just tryin to save some $
Thanks in advance!

Welcome to the forum Matt.

What do you have for a gear ratio?
What do your plugs and wires look like?
 
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Mhurter

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Welcome to the forum Matt.

What do you have for a gear ratio?
What do your plugs and wires look like?

3.73 gears, plugs and wires are new, I replaced them when I first bought the truck under the suspicion that was causing the lack of power while towing. No dice, brand new Delco irridiums, Autozone wires
 

wjburken

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3.73 gears, plugs and wires are new, I replaced them when I first bought the truck under the suspicion that was causing the lack of power while towing. No dice, brand new Delco irridiums, Autozone wires
Hmmm.
It’s been a while since I had a vehicle of this generation so hopefully others will chime in with other things to look at.

Have you performed a compression test?

What does your transmission fluid look like on your dipstick?
 

Larryjb

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Do you have a scantool to check the fuel trims?

You should be able to get 13 mpg at 60 mph. Economy will start to drop off at speed above this, but they shouldn't be that bad. I tow a Trailmanor and get about 15-16 mpg on the highway, but I do keep my speed below 60 mph.
 
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Mhurter

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Hmmm.
It’s been a while since I had a vehicle of this generation so hopefully others will chime in with other things to look at.

Have you performed a compression test?

What does your transmission fluid look like on your dipstick?
 
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Mhurter

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I have not run a compression test yet, trans fluid is not perfect but still pink and full. Planning on doing a service soon.
 
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Mhurter

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Do you have a scantool to check the fuel trims?

You should be able to get 13 mpg at 60 mph. Economy will start to drop off at speed above this, but they shouldn't be that bad. I tow a Trailmanor and get about 15-16 mpg on the highway, but I do keep my speed below 60 mph.
I do have a scan tool, I’ll check fuel trims when I get home tonight. For the record, towing an is300 on a uhaul trailer, I got 8mpg, @70mph
 

Larryjb

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This is from an old ebay ad, but this like my Trailmanor. The low profile helps tons with economy, plus this is a lightweight trailer. Your uhaul may be heavier and taller.

trailmanor.jpg
 

Tonyrodz

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Hey guys! New to the forum, but not new to the gmt800. Had a 2000 Sierra 5 years ago, and it was a good truck but it got fairly rusted so I sold it. After a while I needed another truck so I bought an 01 tahoe 4x4 that was mildly lifted with a hair over 200k. I’ve been taking this truck on road trips over the holidays to ensure that I’ve gotten the kinks out of it, and I noticed that this truck is getting HORRIBLE fuel economy on the highway. At 70-75 I’ve been getting 13mpg! My old Sierra would get 18 easily at that speed. So I’m wondering where I should go to try and improve fuel economy. I’m planning to change all the fluids in the trans, diffs, and tcase with synthetic, but I’m also looking for things I can do to help fuel economy on this thing such as programmers, intakes, exhausts, etc. as a side note, this truck seems significantly down on power from what I remember of my Sierra, no DTC’s set though. Truck is stock besides a stereo and 33” duratracs. Any info y’all have would be appreciated, just tryin to save some $
Thanks in advance!
How mild of a lift? Could be a combo of the lift us tires that's causing the mpgs. How's your front end alignment?
 

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