rel3rd

iTrader: (42)

So...I have a 2002 Z71 extended cab, short bed truck. Had it 3 years or so...

When it was bone stock, it got 16mpg's MIXED driving and once or twice got 17mpg's...MIXED stop & go/highway driving. I don't do any long trip, highway only driving, so there's no way I can check that.
With the long tube headers it dropped to 13mpg's until I dialed in VE, MAF, and slight tweaks to timing. Then it went back up to 16mpg's, although runs much better than stock. My short term fuel trims are never more than 2-3% + or - . My long term fuel trims are always less than 5% + or - . My KR is ZERO, and truck is tuned for 87 octane unleaded gasoline.

So here's where the myths come in. (Myths as far as MY TRUCK is concerned)

With leveling kit and big heavy rims/2" taller tires = 16mpg's
Lowered via 2" drop spindles, stock keys, 2" shackles and rear blocks removed, stock 17" aluminum wheels = 16mpg's
Same as above, but with heavy 20's = 16mpg's

Tuned for best performance and lowest fuel trims on 87 octane = 16mpg's
Tuned for best performance and lowest fuel trims on 93 octane = 16mpg's

Open bed, tailgate up or down = 16mpg's
Lightweight roll up tonneau cover = 16mpg's

Drive like Grandma and make honest, conscious effort to save gas = 16mpg's
Drive like a jackass and no regard or care for mileage = 16mpg's

AC off and windows down = 16mpg's
AC on and windows up = 16mpg's

Before electric fan conversion = 16mpg's
After electric fan conversion = 16mpg's

With stock airbox, stock air tube, stock throttle body = 16mpg's
With modded airbox, 4" air tube, ported TB = 16mpg's

If you haven't figured out the pattern here yet...my truck gets 16mpg's no matter what. Only time it varies is when we have the winter blend gas, and then it may drop to 14-15 pretty steady...

BTW, I don't rely on some onboard instant MPG reading. I fill up at same pump, same station, same everything and check mileage with simple division, every fill up...Miles traveled divided by gallons to fill tank = true MPG's. Speedometer is "tuned" using my HPTuners and a GPS.

So here's my final thoughts.

1. Not every mod works the same on every truck (or car). In other words, no guarantees of anything just because Joe Blow supposedly got this or that...
2. Lowered or leveled, stock or heavy aftermarket wheels makes no difference whatsoever for me.
3. Same exact mileage and very minor change in performance makes the 93 vs. 87 octane battle non-existent in my world.
4. If someone stole my tonneau cover and tailgate, I'd still get 16mpg's.
5. Much more fun driving like a jackass with no regard for gas mileage.
6. No idea why anyone would NOT have or use their AC when needed.
7. Electric fan conversion works very well as far as cooling, and seems to rev quicker, but no mileage change as many others claim.
8. According to multiple datalogs, my home-made fresh air setup works as it should, but makes absolutely no difference in mileage.



I experienced the same type results on my baby cammed 2000 SS Camaro.

With a few hundred passes under it's belt, and with many being datalogged, my car ran the exact same ET and MPH with a closed SLP dual/dual catback as it did with an open cutout. Same exact numbers with 410 gears as it did with 342's. Same exact numbers with $1000 worth of adjustable suspension parts, as it did with stock suspension...

Bottom Line: I guess I am condemned to 16mpg's no matter what...

TIM Z

iTrader: (12)

Hmmm, good read bud!

I guess the 14 mpg i get with mine when aint bad then.

Your right about false mileage claims , but i dont see a tornado on your mod list haha.

Hows the leg?

rel3rd

iTrader: (42)

Leg's doing ok Tim. Thanks for asking. Still nowhere near 100%, but getting there slowly but surely.

I'd trade my 16 for a blown 6.0's 14 any day of the week.

dlt76028

iTrader: (13)

I'd take 16mpg

TXsilverado

iTrader: (19)

i dont check my mileage. 4.30 gears and 4400 converter is rough lol.

gnd111

iTrader: (1)

Open bed, tailgate up or down = 16mpg's
AC off and windows down = 16mpg's
AC on and windows up = 16mpg's


Exact same conclusions on Mythbusters...

I only get 12mpg with my 404ci...

TXsilverado

iTrader: (19)

cover the truck in clay and cut golf ball holes into it. that worked for the mythbusters.

03LQ9

Running with the AC on should drop mpgs, it will show up instantly on any truck with the instant fuel economy read out when you turn it on. With my truck turning on the AC raises the injector duty cycle about 3% ( e85 ). Electric fans almost always give better economy but its never usually that significant. Mysthbusters did find that running with the tail gate up gives better mpg becasue of the way the wind circulates in the box with it up.
My trucks mpg never changed with exhaust and headers as well. If I beat on my truck the economy drops pretty significant. When I changed the 4l60e for a 4l80e I lost 1-2 mpg.

rel3rd

iTrader: (42)

My wife thinks I am nuts for checking it every time I refill the tank. I told her it's habit and it actually can tell you if/when something is wrong...Checking mileage at every fill-up is how I found out my motorcycle's carb was screwed up...mileage dropped nearly 6mpg's from one tank to the next even though it seemed to be running fine. After 3rd tank of same results, I knew it wasn't a fluke. Fixed the carb and actually now get 3 or 4 mpg's better than ever. It's a 95ci 100hp 700# Harley with a fatass 290# operator so it definitely shows a big change when ridden hard.

Surprisingly, the truck doesn't change no matter what. If I didn't check every tankful from when I bought it until now, I'd be guessing if it was better/worse/same as when stock, but I check it every time. Takes all of a minute to do and it's more accurate than any factory gas mileage readout.

My wife's Lincoln SUV reads 12 on the highway and as high as 60+ coasting downhill, lol. Checking it with a calculator, at fill-up time, it's usually 15 in mixed driving also. 17 on a 150 mile mostly highway trip was it's best...

rel3rd

iTrader: (42)

I agree 100%, but mine doesn't. Maybe it's due to me usually driving it easier when AC is on? I don't know. I do know I have the tune set to turn off AC compressor pretty much whenever engine has a load on it which surely helps. I figured as cold as these truck's ac systems get having it cycle more doesn't affect how cool it stays in the cab...at least I haven't noticed it enough to be concerned about it.