Repair-It

The 4.3L V6 has been redesigned for the first time since like ever! It actually never made it past the ~195hp Vortec days of the mid to late 90s, even as it was available on last year's trucks. It never got Gen III (LS1) treatment like the V8s did. Now it's skipped ahead to Gen V, with all the goodies like variable valve timing, direct injection and the displacement on demand.

Specs:
285hp @ 5300rpm
305lb-ft @ 3900rpm

GM has taken a different approach to their V6 as all the other automakers are now using car-based engines in their trucks. This is a strictly truck offering. It'll tow 7,600lbs. It appears to have some vibes at idle so I guess it is a truck engine. 90° is not the ideal bank angle for a V6.

The crew cab 4WD they tested weighed a porky 5,477 lbs and I think the V6 did fairly well considering.

7.7 0-60
16.0 @ 87mph

The interesting thing that's going on here is that it actually puts out more power on E85. The rating changes to 297hp and 330lb-ft (which you will note is roughly equivalent to the C4 LT1), and the performance does, too:

On E85
7.3 0-60
15.7 @ 89mph

It wasn't long ago that this performance would have been considered quite stirring for a fullsize pickup, with any engine. Actually, the article mentions they tested a VortecMAX-equipped Silverado in 2007 and this 2014 V6 was a tenth of a second faster in the 1/4 mile (on E85).

They also got 3mpg better observed from the V6 vs the V8 (they don't say which).

Apparently the 4.3L was refreshed in 2007. It got distributorless ignition, electronic throttle, the latest PCM stuff....but it was still really the old engine putting out the same 195hp. They must have added these changes for GMT-900.

I know this is an old thread, but I am wondering if they were able to improve mileage while running E85 at all.

Interestingly, if you run E85, you're better off with the 5.3L.

Comparing 2WD:
If you run the 4.3L on regular gas (so E10 probably), you get 18/24, which is better than the 5.3L at 16/23 (combined difference of 1 mpg, which isn't much). Yet on E85, the 4.3L is rated at 12/16 vs the 5.3L at 12/17. I would wager a bet that somehow the 4.3L can't run the cylinder shutdown stuff as aggressively, even though per cylinder the 4.3L is like a 5.7L, not a 5.3L.

In 4WD land, it's the same thing. The 4.3L on regular gas gets 17/22 while the 5.3L gets 16/22 (diminishing returns again). But on E85, it's 12/15 for the 4.3L and 12/16 for the 5.3L.

The worst part is, by averages it makes no sense to run E85. It costs less to fill the tank, but it actually ends up costing more per mile when you factor in fuel economy.