25 mpg Silverado Z71

[Frank Lee]

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

[Christ]

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.

[Frank Lee]

'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://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.

[Christ]

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.

[RH77]

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.

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

Originally Posted by Frank Lee

'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.

[Frank Lee]

*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.

[Christ]

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.

[Frank Lee]

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.

[taco]

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.

[Christ]

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

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