Ethanol and Cylinder Deactivation: '08 Impala
 

I'm currently in the midst of renting a 2008 Chevy Impala LTZ with the 3.9L V-6 "FlexFuel" engine and "Active Fuel Management" (the GM "LGD 3900" engine).

One tank of 4-passenger driving, with an average of 52 MPH, resulted in 24.3 MPG. The advantage to this engine is the the cylinder deactivation and E-85 capability. This engine was tested in the Monte with a non-Ethanol compatible engine a month ago or so. The 3-Cylinder engagement proved to offer no advantage to the 3.5L base engine, or to that of the regular 3.9L. Will Ethanol offer more available power and torque to shut down half of the cylinders, more frequently?

One more day will tell. A relatively full tank of E-85 is nearly empty from this cross-Missouri expedition. (for those in another post, I passed "Nostalgiaville, USA twice, argh). Bo-ring. MO I-70 sux.

Previews: With Ethanol, 3-Cylinder operation holds on longer with the added octane rating and available power-to-load calculation. Even still, FE is much lower, begging the inquiry: is it worth it? I paid $2.40 per gallon for E-85 vs. $2.90/gal. for 87-octane regular. Tomorrow will reveal the final tally...

RH77

Aaahh...Nostalgiaville, USA. Good times, doesn't the bright pink paint just about make you go blind?

Anyway, I have a buddy who uses only E85 in his Taurus, I calculated it up for him once and showed him that it has to be at least $0.60 cheaper (I think, it's been a little while) than a gallon of regular for it to be worth it. In Columbia, MO it was usually only about $0.50 cheaper

And yeah, I-70 is awful. I particularly like the stretch I think it's just West of Columbia where there's a sign denoting it "Pearl Harbor Memorial Highway" I always quip that they must have salvaged the road from one of the decks of the bombed-out battleships at Pearl Harbor.

Rick,
I don't know about the V6 but when I was testing ethanol on the Daewoo-woo I had an increase in FE at E15 and once I hit a mixture of E25 the mileage dropped off slightly up to a mixture of E50( 12% decrease at E50). Above E50-E85 it dropped about 25%. So you might be able to run a mixture of E40-50 and not lose a lot FE and come out ahead on the price or just break even if emissions is what your looking for.

I think on the bigger engines I remember seeing data from toyota that E30 was kinda of the sweet spot for it and there was not much decrease in FE(5%) at that mixture. Maybe ELF can chime in I think that's what he ended up running.

How many miles on it rh?

Results
 

Here are the results:

The second tank resulted in 19.8 MPG over 288 miles. 3-cylinder operation is better in this 3.9L than the non-Ethanol models due to added power/torque overall. 3-cylinder operation helped somewhat, and is enhanced by the octane of the ethanol to unlock some power. Speeds at 45-60 mph are helped the best with 3-cylinder mode -- anything faster, and wind resistance forces all 6 to kick-in.

The conclusion is that the standard 3.5L can get you plenty of power and near-30 mpg operation on the highway, which seems to be a better fit. Instead of the stout 3.9, they make a 3.5L Flex-Fuel (I may run across it to test), but a full tank of E85 seems to really hit the bottom line.

Maybe that's the problem -- I usually run Ethanol test cars to near-empty before fueling. Perhaps a half-tank fill would be a good compromise.

Furthermore, cylinder deactivation seems to be just an excuse to use a bigger engine where a smaller one will more than do the trick -- in this application.

Finding E-85 is also real challenge. The Internet helps, but many stations have either abandoned the fuel, or it's being planned for the future. You get there, and there is none.

Roughly 9k-10k miles.

The car is identical in many respects to the many other Impala/Monte varieties I've driven since it's last redesign. In this case, the top-line LTZ model offers 18" wheels, and a rough ride that passengers notice. I didn't notice a huge improvement in handling for the sacrifice in ride. The 1LT model with the 3.5L engine is sufficient, in this writer's opinion.

Up next, I'm testing a Saturn Vue V-6 with a 6-speed automatic. It's essentially an Opel Antara, reworked as a Saturn. Also, I had the pleasure of putting 1100 miles on a Mazda 5 -- what a versatile, efficient machine!

RH77

Hmm I love E-85, the things that bother me is why use big engines and cylinder deactivation? A turbo charged engine can provide the same amount of power, with out the ridiculous waste of energy required to spin three spare pistons around. With E-85 this is even more true. A relative octane rating of 105-110 allows much more power to be made from the same size engine by turning up the boost safely.