4.8 vs 5.3 questions

So seeing as im basically new to this forum AND trucks i had a few questions that i figured someone could explain better than google.

1. I have a 08 4.8 silverado. Who makes a supercharger for this? and why doesnt the 5.3 one fit if its the exact same setup as the 4.8?

2. Me and my buddy have the EXACT truck. Both 08 short bed regency after-style, with 275/55 20 wheels and tires. The only diff is he has a 5.3 and makes 15 mpg and i make 12 in the city. Thats with a K&N, shorty headers, and 93 octane tune from nelson. I also have a cutout and im testing that to see if it helps my mpg any. So what im asking is, why does he get better MPG than me?

3. Id like to get the acronyms cleared up so i dont sound like such a noob spelling this stuff out.
what does nnbs, sss, ect. stand for?

this forum has been a wealth of knowledge so far
i really appreciate it, thanks in advance

I'll do the easy part, nnbs = new new body style or GMT900, SSS = silverado SS. There is also an acronym guide on here somewhere. Oh for what its worth, FWIW, my 07 GMT900 got 17 mpg in mixed driving, completely stock plus the NP tune. Maybe you have a brick for a foot?

this is possible, but even if i lay off the gas it only goes up maybe 1 mpg.
bahh maybe ill change the plugs and wires? also i owned an srt-4 before my truck and the thing to get on that was the msd (sp?) wires, is it the same for silverados? and plugs, if heard its just a bunch of hype with the different stuff you can get. Any opinion on that?

factory wires are great. Stock plugs usually last 100k+ without issues. Is your convertor locking?

when you ask if its locking, do you mean is the tranny slipping? or does it try to take off with the brake on? If yes, then no to either. It does shift pretty stiff though, it did that even when it was stock.

was wondering if it locked the convertor at cruise speeds. Usually the convertor is unlocked except in OD, meaning the engine speeds change easily if you give it a little more gas while the MPH doesn't change much.

im pretty sure its unlocked, although im not really sure. Whats a good test to figure this out?
Also are you concerned if its locked and stayed locked?

I would be worried that it never locks, hard to get good fuel mileage when the engine is revving too high and not doing anything productive.

i dont think thats the problem cause it drives and rides like my friends. If you know a test i can run it through ill try it and report the results

Do you use the driver information center readout to see what your instant fuel mileage is while driving?

Haha i wish i had that. It would be easy just to look up and see it but my truck didnt come with it

Your dash panel on the left side of the wheel where the headlights are, you don't have the four button DIC panel to the right of the a/c vent?

Here, buy one of these, remove your stock panel and reinstall this one. The wires for it are behind your dash panel.
GM Parts Direct: Your direct source for Genuine GM Parts

Whats the little button for?

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Originally Posted by Goat08

...2. Me and my buddy have the EXACT truck. Both 08 short bed regency after-style, with 275/55 20 wheels and tires. The only diff is he has a 5.3 and makes 15 mpg and i make 12 in the city. Thats with a K&N, shorty headers, and 93 octane tune from nelson. I also have a cutout and im testing that to see if it helps my mpg any. So what im asking is, why does he get better MPG than me?...

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dude, my 01 5.3/5 spd just got 16mpg mixed on this last tank.
that's with 4x4, airaid, blackbear 93 tune, mellowtone catback. the real kicker was that this tank was mostly WOT runs (for filming exhaust comparisons & running dynolicious), 75-90 on the interstate (2 separate unavoidable issues that made me have to get to work fast), and some up/down shifting practice.

Omg this is ridiculous. why is my MPG so bad? I mean yeah i hit the gas alot but why should it be any different than the next?

Quote:

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Originally Posted by Goat08

Whats the little button for?

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Little button? There is an opening for the headlight switch and the dimmer switch you have to transfer over from the original panel. The little button on the instrument cluster? About all its good for is trip setting. They swapped a set of GMC wheels onto my truck at the dealership and I automatically have 4 wheel air pressure sensors on the truck, not sure if the stock worktruck has them or not but they probably do.


Drive like there is an egg between your foot and the pedal and mileage will increase. Is your airfilter dirty? Do you have any engine codes? Could your cats be clogged?

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Originally Posted by RedHeartbeat

...Could your cats be clogged?

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i sure know mine ain't!! i've spent the past week blowing them out quite nicely :naughty:

Quote:

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Originally Posted by RedHeartbeat

About all its good for is trip setting. Is your airfilter dirty? Do you have any engine codes? Could your cats be clogged?

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I already have a trip setting, i can use the little knob in my instrament cluster to set the trip timer just like on every other car. Thats how ive found out the MPG so far.

no engine codes, and if sound is any indication of cats being clogged then my buddys 5.3 is louder than my 4.8. I just figured it was his bigger motor. How to you test that out?

FWIW, the DIC panel give you access to a whole lot more data than the trip meter button on the instrument panel.

testing for a clogged or restrictive cat takes a pressure gauge or a laser type heat gun to measure if one cat is hotter than the other.

Bigger engines are louder, I have the stock 4.8L exhaust on my 408 engine and its is distinctively louder.

well the test will have to wait till im back from the job im on in louisiana. I plan on getting an ORY pipe and putting a single 3" cat after my cutout, that way im still legal but when i open the pipe its free flow