25 mpg Silverado Z71
 

I have a 2006 Chevy Silverado Z71 that can use regular unleaded or any of the ethanol mixtures. I noticed fuel economy is not very good with the ethanol, so I decided to try some hypermiling techiniques on a trip I made. I wanted to keep things simple, so the only things that I concentrated on was keeping the tach below 1,700 while accelerating and going up hills and I would also put the truck into nuetral when going down hills.

I normally get about 17 mpg with this vehicle. On the first leg of the trip, I had heavy headwinds (30 mph with gusts to 50) and was driving through rain most of the way. On that leg, I was able to get just shy of 20mpg. The next day was calm with no water on the road and I was able to get 25 mpg with this vehicle.

I thought this was pretty good for a truck with available 4WD and a 327 V8.

If you optimize for gearing, maybe add a relatively aerodynamic bed cover, I think you could easily break 30mpg.

If I could break 20 again I'd be tickled pink. What's yer truck got?

My bets on cylinder deactivation, and dammit, I'd bet my left nut that even a full size truck could get ~35mpg at 55mph w/ the Phil Knox aero treatment, LRR tires, and some way to manually actuate the cylinder deactivation doohickey.

McCool, sorry I did not find your fuel log or vehicle in the garage... Could you fill in the details, you say

"I thought this was pretty good for a truck with available 4WD and a 327 V8."

does this mean you have the 5.3 liter 4WD or the 4.8 liter base model 2WD and put the Z71 stickers on it?? I have the 2002 1500 Z71 with 4WD and have been tracking fuel economy for 32,000 miles in the past 18 months and my best tank was 21.06 mpg with a lifetime average of 17.32 mpg. I have a scangauge and can achieve high mpg coasting down hills and driving on flat roads at slow speeds but overall results are going to even out.
If you have discovered some trick to coaxing out 25 mpg from these rolling bricks without any modifications (computer, areodynamic, or mechanical) Believe me you have our un-divided attention.

I'm guessing he has the 5.3L engine (323 cubic inches). My company "brick" has that engine, an automatic transmission, 2-WD, and a soft tonneau. I don't bother to employ all of the tips and tricks that are discussed here while driving it. But....around town, it's typically a 17 MPG thing. On the road, running at the speed limit (on cruise) it is a regular 20-21 MPG thing, and I have seen the better side of 24 on several occasions. I too have not bothered to post logs (busy), but I do keep hand-calculated mileage logs in all of my vehicles, and I fill them up the same way each time (not to the pump "click-off" point). I have to admit that I am pleasantly surprised that Chevrolet's ads seem to be correct - "20 plus MPG". I know that mileage figures in the "20s" pales in comparison to what some of the real experts here are doing with hypermiling the small, efficient, modified cars, but....the pickup truck thing is unavoidable for some of us. And "twenty-anything" is a great figure for a full sized truck. Congrats on your mileage!

i managea a 200 mile trip in my dads 08 silverado crew cab lt 4x4 z71, with the 5.3(327) 4 speed auto w/ 20's. i watch the gauge on the dash, and u can hear the cyc deactivation in his duel flowmasters, it sounds kinda funny. i got just shy of 25, i think it was 24.8, never went over 65mph.

but he gets 15-16 out of it normally.


still great for a full size.



i also hook up the sg to my friends 01 or is it 02 silverado reg cab 4.8 4x4 5 speed, and found it did 30 mpg at 40mph.......and 5th was useable down to abotu 15-20 mph. u could accelorate right out of it no studder. but a tiny bit of peddle it was 15mpg. haha just goofing off alittle i got low 20's mpg.
(k&n intake, eldbrock header, true duel exhaust w/ thrush and a diablo tune. not exactly stock and required premium)

My suburban does 18mpg average with the cruise on 70-72mph. It will do 25mpg at 45-50mph. Are you guys going by the DIC or hand calculating. I found that the DIC in my burb is heavy optimist. I have gotten as good as 22mpg in mixed use but it was impossible to maintain that. The DIC was reporting 24mpg+ of course. I wish it had the cylinder deactivation. I feel the system is good for 20% improvement around town, more in skilled hands.

All my results are based on hand calculations. The 2002 does not have the driver info center or cylinder deactivation, wish it did. on anoter site I also frequent GM-Trucks.com there are guys on the forum getting their computer reprogrammed to eliminate cylinder deactivation so they have all V8 all the time. I don't know why...Does anyone know if Cylinder deactivation can be programmed into a computer program that does not have it??

My results resemble yours closely. My average FE is around 15mpg all city. I'm considering a chip. I've heard of some people getting better mileage with chips on the truck forums.

"Does anyone know if Cylinder deactivation can be programmed into a computer program that does not have it??"

How would that work?

I think, and I'm not completely sure, that GM's cylinder deactivation simply shuts off the pulse signal to the electronic fuel injection to certain cylinders to only fire 4 or 6 in a V8 depending on power requirements. the coils still fire a "waste spark" and the valves still open and close off the cam shaft lobes just like as if the cylinder was producing power with a fuel charge. I assume this is all computer controlled by the PCM (powertrain controll module) So if the computer can determine shift points, fuel injection pulse widths, fan on and off, etc. all based upon sensor outputs why is the power on demand cylinder deactivation not also able to be programmed ??
The pistons are still moving along with all other mechanical parts, there is no seperation so there is still a ton of wasted energy and inertia but for adding a few MPG on low load cruising it is worth it especially on trucks that are not always needed at full power.

ya needz ta do more homework on that

I remember cylinder deactivation on my brothers old '89 bronco... lol idled great, revved great, but couldn't move the truck in 1st gear over a 3" bump on the dirt pad. Took us forever to figure it out, entire left bank was unplugged :P We were amazed it sounded so normal and ran at all.

I see no reason why you couldn't drop 4cyl on highway cruising. It only takes a micro second to fire up the down cyl's when the power is needed. I know my dad doesn't need all 496 ci for driving to work. Hell, that truck would drive fine with 6 cyl 90% of the time. It doesn't need all 320hp and 480ft-lbs on tap, only when pulling or climbing.

Someone should get aggressive with the cyl deactivation, and see if you can daily a 1/2T or 3/4T on 6 or even 4 cyl. That'd amaze me more than squeezing more hp/ci.

u can hear the sound in dad's exhaust ,(it is an odd sound) before the displays says v4 mode. it also says at 65 on flat ground will go from 15-18mpg to 22-25 mpg( instant) on the display. i wish there was a ecco switch, where u could keep it off.
i have noticed it is not speed dependant but load. caus it iwll work from 20-80 mph(fast as i have had the gutless wonder)

I don't think this is correct; pumping those "dead" cylinders with the valves still working would draw tremendous amounts of energy; I thought the reason we just now were seeing this cyl deac. technology was that valves can now be opened via solenoids to let dead cylinders "breathe", or something involving variable valve timing. Of course, I may be talking out of my arse...:p

Sounds like my mustang - we ran out of cash when building it and I destroyed my oem camshaft:eek: so my buddy convinced me to put an F-150 cam in it. It runs pretty well, a good amount of power and torque, which I attribute to the truck specs, but last year (about a year and a half after fixing the car) I found out that two of the cylinders on the F-150 firing order are opposite what they are on the mustang, so I've got piston, ignition, and fuel events happening at one time, and valve events happening at another. I can't wait to see how much power and MPG I can get when I get a good cam for it.

I have never had much luck with cylinder deactivation in Full-Sized, V-6 cars: Impala, Monte Carlo. 3-cylinder mode (as indicated by the dash indicator) would hang on until the load built-up and cycled back into 6-cylinder mode. On the highway, this was quite cyclical at 65-70 mph and didn't show much gain at all in FE. Some engines were Flex-Fuel equipped, and allowed better performance of the AFM system with E85, but was entirely subtracted by the poor FE of E85.

(For the record, GM's "Active Fuel Management" is a mechanical process of manipulating valves -- it cannot be programmed if not equipped".

55-60 mph seemed to be ideal. The wind resistance was light enough to keep the load figures down and keep it locked-in as a 3-banger. Suburban-enviroment FE improved as well (~45 mph).

So, the trick with the pickup might be to monitor the load and figure out the parameters that it locks/unlocks. IIRC, the Imp factored a load of ~50-51% and full TC lockup. Reduce this through technique or mods could get you that elusive 30 mpg with the pickup.

-RH77

I'm more than a little peeved with my F150. Went through the brakes so they don't drag, got new highway tires (slightly taller than stock) aired to 49 psi, mechanical fan delete, no idling- warm-up on the go, cruise at about 52 mph and what do I get? 14.6 mpg on tonight's fill. :mad:

Don't lose heart, Man. Are the temps, around the zero-mark or less? I've been getting really crummy mileage, as is usually around this time of year. With the winter fuel, crappy rolling resistance, longer warm-up times, lower IATs, etc. it's tough. Apply those techniques in warmer weather, and I'm positive that the results will be a heckuva lot better.

-Rick

Guys talk about an easy 30 and at <15 that seems a loooooong ways away...

Frank - you're working with a wholly different beast!

IMHO, some carb tuning would benefit you greatly in that F150 of yours (I'm guessing it's an older truck, possibly with a 300 I6? Most of the I6's power is in the lower end. It's capable of revving up to make even more power, but requires extensive work to do so reliably.

Most of the sluggishness in the 300 is in the restrictive intake and exhaust design. Not to mention the intake is heated by the exhaust manifold, since they bolt on the same side of the head, and interlace each other.

Solving a few of those problems will probably get you on the way to much better fuel mileage, I'd say.

'94 F150 4WD super cab short box 5.0 V8 EFI, E4OD a/t
'06 Silverado 4.8 V8 4sp a/t No mention of cyl deactivation.

They could be quite similar. Fuelecon.gov shows 14/15/18 for the Chev and 12/14/17 Ford.

Yes it has been bitter (waaaay below zero) cold lately. But I haven't used it much lately either. Yoosta figger 18 mpg average when it was a newer truck. Maybe at 108M it's time to replace O2.

P.S. It has these Dayton Daytona SR tires:

http://i146.photobucket.com/albums/r...8356bba0d8.jpg

http://www.regionaltire.com/showcase...d=80&Type=3009

Haven't found any r.r. data on them, but they were the "ribbiest" (vs "blockiest") treaded tires at the store.

I retract all previous statements... I currently know nothing specifically about your truck, so only common knowledge applies.

We now return you to your original programming.

It sounds like something is amiss. Do you have any data for the RR of the new tires? Have you given it the ol' Seafoam treatment lately?

Put ya some straight-thru dual pipes on 'er. That'll do ya up nice, don't ya know. :p

Knowing your vehicle expertise, I expect that the engine is in good tune. On that transmission, can you force-shift into 2nd? I used to drive E-350s with the same tranny (7.3L IDI -- among 4 or 5 models in the fleet, they all shifted pretty hard and had odd TC lockup behavior -- around the 2-3 shift point).

Regarding the Oxy Sensors, they should last beyond 100K, but the age might be a factor. The output might need a quick scan from the multimeter.

Last inquiry -- do they require emissions testing there? If so, that might be a window into what's going on.

-Rick

*Smacks head*

Of course! I forgot to pull the muffler off! Fer sure I'll do that before anything else!

L O L You know I'm kidding. ;)

I lift up on the accelerator at 42 mph and therefore force O.D. and converter lockup from that speed on up. I don't think I could lug it a whole lot more if it had a stick.

I guess O2 performance can slowly degrade over time, not just work and then suddenly fail. Engine sure runs nice, no missing, no smoke, no flat spots, no CELs, good power, etc.. I just haven't found the magic formula yet.

Maybe there's a pill I can put in the tank???

P.S. No emissions testing here.

Throw some corn oil in the diff... LOL.

Seriously - when's the last time you checked the diff fluid? That can account for a huge loss in MPG and power. There has to be some frictional losses going on somewhere that aren't accounted for.

Yes good idea. I should change out both diffs, xfer case, and a/t juice for some new synth goodies. 30 here I come! No, really, it's time for new fluids regardless.

talking about silverado/ seirra
i found somethin odd in a few of them 07-09 that my family own, they seem to cut the alt out on low loads and the volt meter will drop to around 12, for long periods of time, then when needed it will jump back up to 14.

odd, chevy has pull out all the stops, no uneeded holes, e-fans, cyc deactivtion, airplane gears.




if your 302 gets to 30mpg for a few tanks, i will sell my toyota i4 4x4 and or give it away.

Taco - I call dibs! I'll even come pick it up!

Frank - I'm countin on ya, buddy! Get those 30mpg tanks!

I'd love that but...

Don't hold yer breath!