1996 Silverado K1500 Fresh Meat

[ECO-AKJ]

If you have stock tires, you could go to a 215/85/16, similar in height within about 1/2in or so, although it may be tough to find in a non-LT tire.

Side skirts, you could use lawn edging for that.

[vteco]

Originally Posted by aerohead

A) it would be helpful to know GM's motor oil recommendation for 'winter' operation.
B) does your transmission use DEXRON-II ATF ?
-snip

Thanks greatly, guys! I'll answer the questions as soon as I can. The truck is garaged 20 mins. away right now..awaiting repair of a slow fuel leak near the top of the tank (tank? lines? fuel pump?) -- it will be into the shop for that on the 10th -- after that I can drive it again and start testing, etc. to provide those kinds of baseline answers.

I will do the warm-up as you specify, aerohead.

For the things I can answer now:
A.) 5W-30 is what I can find in references online
B.) ATF orig mfr spec: Dexron III (4l60E transmission)
C.) Rear Diff 3.73 ratio, GT4, orig mfr. spec: 80-W90 GL5 (not an LSD)
D.)Tires: P265/75R16, (I'll measure actual OD when back at truck)
E.) Tire types: Possibly, I'll have to check what I have now, not sure.
F.) I don't think the K is taller than the C. But not sure.
G.) I don't know actual curb weight, labeled GVWR is 6200, saw conflicting curb weight figures online.
H.)Will actually measure HxW. I believe the GMT400 (mine) series is sleeker than C/K10 series.

Thanks for all your info!

[ECO-AKJ]

Tires are my jam...I was working the parts department at a Ford dealer when the Firestone Recall hit back in 2000, so I learned a lot about tires at that time, and now I can research most tires that I deal with daily. The only thing I hate about tires is having to move them, I used to work at a dealer that didn't have carts for tires.

A P265/75/16 calculates to 31.643 inches.

A 235/85/16 Calculates to 31.722 but is 1 3/16in (roughly) narrower.

[vteco]

Thanks Eco-J. I will keep that in mind when I need new tires.

Also re. curb weight, I've found the payload capacity is listed as 2069, which would, if correct mean empty weight is 6200-2069 = 4131. But I don't still actually know true "curb weight".

[vteco]

The back tires are new, the fronts will need replacing in maybe a year. Is it possible to run with the narrower 235s on the front while still using the 265 rears until worn, assuming the diameters match as mentioned above?

[ECO-AKJ]

Originally Posted by vteco

The back tires are new, the fronts will need replacing in maybe a year. Is it possible to run with the narrower 235s on the front while still using the 265 rears until worn, assuming the diameters match as mentioned above?

It isn't recommended, however, it is possible as long as you don't put it in 4WD.

[vteco]

Originally Posted by aerohead

I) the normally-aspirated 5.0-liter's torque peaks @ 2,800 rpm, with 134- bhp available at the flywheel.
J) the engine's brake thermal efficiency ( BTE ) won't be any better than about 36%.

Nope, this is a "Vortec 5000" engine. Wikipedia:

In C/K trucks, the 5000 produces 230 hp (172 kW) net flywheel at 4600 rpm and 285 lb⋅ft (386 N⋅m) net flywheel torque at 2,800 rpm.

[aerohead]

For the Vortec 5000 @ 40-mph:
1) with your tires, the rear axle is turning at 424.82-rpm
2) the output shaft of the trans. is at 1584.58-rpm
3) and engine is at 1,191.41-rpm
4) running at approx. 23.64% brake thermal efficiency ( BTE )
5) and an available power of approx. 59.57-bhp
6) with maximum BTE occurring @ 77-mph,
7) and optimum HWY economy @ approx. 55-mph.
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8) Your engine oil appears to already be virtually optimized.
9) same for the DEXRON-III Mercon, with pour point, cold & hot viscosity better than DEXRON-II, and as 'good' as PENTOSIN ATF-9, in use today with 20,000-rpm electric motors and supercar ZF transmissions.
10) The rear axle diff lube might benefit a smidgeon, if 100% synthetic, if it maintains the 'GL5' capability.
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11) If your 'use' of the truck could be maintained with 'ALL-SEASON' radial tires, their lower rolling-resistance would have a high probability of demonstrating higher mpg at your target speed. 'All-Seasons' have the lowest power absorption coefficients of all passenger car tire types manufactured.
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12) Under the ground rules for aerodynamics:
A) drag force reductions at 40-mph, will be 36% less effective than at 55-mph.
B) power reduction associated with drag reduction at 40-mph, will be 61.5% less effective than at 55-mph.
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13) Since 'engine friction' IS 'hydrodynamic' friction, just as with an aircraft wing:
A) automotive lubricant 'friction' is 'RULED' by kinematic viscosity.
B) kinematic viscosity is ruled by ambient temperature and pressure.
EXAMPLE:
* 5W-20 full-synthetic motor oil has a viscosity of 340 centiStoke ( cSt ) at 0-C
105 cSt @ 20-C
47.8 cSt @ 37.8-C
and 8.1 cSt @ 98.9-C.
* In Vermont, on a 35-F day, the cold-cranking viscosity of this oil would be almost 42-times as high as on a fully-warmed summer day, where:
- engine oil @ 214-F
-coolant @ 203-F
-transmission @ 188-F
-Differential @ 159-F
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The USEPA considers that tires are 'COLD', at 70-F.

[Gasoline Fumes]

0w-30 should be a safe replacement for 5w-30, and should increase efficiency in cold weather and short trips. Going thinner on the higher number might be OK, but an oil analysis might be a good idea to check for excess wear.

[vteco]

Thanks aerohead and gasoline fumes, that's a lot of information! I appreciate the work involved. I think the Dexron 3 is no longer available, and is to be replaced by Dexron VI.

I bought the truck used and have never replaced ATF, so replacement and filter might be a good idea, since it's an unknown quantity. Same goes for the diff. It's a 250,000 mile vehicle.

It's also coming up on oil change time, so I could switch to 0W-30. I have not used synthetic oil in the past, but will try it this time. Temps with a high in the 30's here would be considered a warm day until at least March. Even sometimes April.

I'll be thinking about new tires next spring, based on what you all have been talking about.

Shift point mods with the new PCM tuner, and aero mods will be possible to work on after Dec 10, when the truck is back on the road after fuel leak repair.