What We Tell People

[Big Dave]

I accidently came across a copy of the local paper where I had been interviewed about how to improve MPG. This was from May 2008 when gas prices were near their peak. Like most people who get asked such things, I gave them the old clichés about air up, slow down, tune-up, yadda, yadda, yadda. As Kevin Kostner in “Bull Durham” told the rookie: “Cliches are your friend.”

Fast forward to this spring. I buy a 1996 Impala SS (I always wanted one of those) as a driver while I get more aggressive on the pickup. A bit of work tracking down the usual used-car gremlins and trying to baseline the car in case I get the urge to ecomod it. It is a great driving car.

But the critter seems immune to the old chestnuts. I can hypermile my brains out or drive it like Tony Stewart (a very aggressive NASCAR driver for you non-US guys) and regardless I can throw about 1.5 MPG over the whole range. I’m running 60 psi in the tires (20% over the sidewall max). No joy. The car coasts well. But regardless, it gets 20 MPG plus or minus 0.75 MPG. The car is 35% lighter than the pickup but gets 30% LESS MPG.

If this were a truck, I’d say it is overgeared. MPG insensitivity to other measures is a classic symptom of overgeared trucks, but this car has 3.08 gears – pretty long-legged by today’s standards.

I think the big factors are the gas engine and the automatic transmission. The LT-1 runs nearly completely throttled and inefficiently and the torque converter is built for a high-powered engine and feels “loose” to me.

But, when you think about it, this is the vast majority configuration – gas engine and automatic transmission. Like it or not, this configuration is very resistant to the old chestnuts. So when we spouted the clichés, people tried them and got no results and they figure we are full of the brown & smelly stuff.

So, when (not if) the price of gas & diesel goes up again I am gonna change my tune. I’ll tell them:

1. No clichés. I presume you are smart enough to properly maintain your car.
2. If you drive less than 7,000 miles a year, don’t worry about it. Any meaningful action will cost more than it is worth.
3. If you drive enough that it hurts, trade in your Sequoia (euphemism for any SUV)for a Prius (euphemism for any high-MPG car). Take the trade-in beating and enjoy the good MPG.
4. If the price of fuel hurts enough but you really need a Sequoia or Tundra, you’ll have to become a form of hot-rodder to live with it. You’ll come to see the basjoos-mobile or Phil’s T-100 as beautiful, you’ll do an engine and transmission change to a diesel with a stick and you’ll change you gearing and put those Goodrich Long Trail TA’s (low RR 16 tires) on the vehicle.
5. Don’t waste your money on snake-oil solutions like acetone, two-stroke oil, or Brown’s gas.
6. Small modifications general get small results.

[tasdrouille]

The clichés have been tried, tested and proven effective on most of the vehicles. An AT by default makes hypermiling harder because you have to fight it most of the time. I tell people with a MT not to fear rolling heavily into the throttle and shift early, but I can't tell people stuck with an AT to punch it, because they have mostly no control over the shifting. There are so many variables that affect fuel mileage that the best advice to give people would be to head over here. But since very few people will do that, my generic advice is to take is easy, slow down and use your brakes as little as possible.

[Peter7307]

Originally Posted by Big Dave

I buy a 1996 Impala SS

I think the big factors are the gas engine and the automatic transmission. The LT-1 runs nearly completely throttled and inefficiently and the torque converter is built for a high-powered engine and feels “loose” to me.

I am not all that familiar with that particular vehicle but it may be either a converter with a high stall speed and lots of slip at normal road speeds or possible a totally shot converter / trans ass'y.

I would find someone who knows these cars backwards and get it them. They should be able to tell you fairly quickly.
Try a local "old school" car club or an internet search.

Pete.

[Big Dave]

Car clubs think MPG is craziness. They all act they are wanting to win the Indy 500.

The car is basically a Caprice cop car with a lower stance and Corvette engine.

[Big Dave]

The old chestnuts are tried and proven but just not all that effective for gas engine/automatic transmission cars (the vast majority).

They do all we tell them and drive wildly out of their comfort zone and get 1-2 MPG improvement. They want more. They think we are nuts and go back to texting while they drive.

Put a diesel in it and improve by at least 40%.

Put in a stick and gain another 20%.

Gas/automatic versions of my Super Duty struggle to get 10 MPG. Straight from the factory I got 18 MPG.

[Mustang Dave]

Originally Posted by tasdrouille

...But since very few people will do that, my generic advice is to take is easy, slow down and use your brakes as little as possible.

That's my advice to people, as well. Some heed it. Most don't. That's their problem.
Following your (and my) advice, my 4 liter Mustang isn't too far behind your 2 liter Elantra.

[cfg83]

Big Dave -

Originally Posted by Big Dave

Car clubs think MPG is craziness. They all act they are wanting to win the Indy 500.

The car is basically a Caprice cop car with a lower stance and Corvette engine.

Yeah, but you don't have to ask an MPG question. Just say you want to control the shifting and/or think you have a sick tranny. If it's an SS I would think that someone had tried to "manumaticize" the tranny. For fun I blinged "+4L60E manumatic" and found these :

Manumatic Technology : TwistMachine.com, CNC Innovations for Hot Rods

...
. An LS1/4L60E [automatic transmission] with a factory computer comes close to meeting all of the criteria, but the computer does not contain manumatic software--nor is their any way to load the software into the factory computer, so an aftermarket transmission computer is still required. Bummer. Don't blame us--blame GM.
Now let's look at availability:
1) COMPUTERS: Compushift, Powertrain Control Solutions
2) MANUMATIC PROGRAMMING: Is loaded into all of the computers listed above. It makes decisions like downshift prevention, manual/automatic mode switching, shift speed, first gear restarts, torque converter lock-up control, snow mode, tow mode, etc. There is much more to manumatic control than just "hitting" the shift solenoids.
3) ELECTRONIC Transmission: Actually the PCS controller will run virtually any electronic transmission. The other brands run 4L60E, 4L80E, AOD-E and 4R70W, 4R100. The key here is that shifting and line pressure are controlled electronically.
...

I am assuming you have the 4L60E tranny because of this :

Chevrolet Impala - Wikipedia, the free encyclopedia

...
The Impala SS was uniquely fitted with a standard 3.08 gear. The limited-slip rear differential was standard (as opposed to the option G80 on caprices) and suspension that was an inch lower. A retuned LT1 5.7-liter (350 cu in) small-block V8 was standard on the Impala SS, making 260 horsepower (190 kW) and 330 pound-feet (450 N·m) of torque (retuned from the prototype's 300 horsepower (220 kW) rating). The primary difference between the LT1 in the Impala and the LT1 that was in the Corvette and Camaro was that the Impala engine was fitted with cast-iron cylinder heads instead of aluminum ones, and a camshaft that was designed more for low-end torque than high-end horsepower. Another difference was that the Impala LT1 had 2 bolt main bearing caps while the Corvette LT1 had 4 bolt main bearing caps. The transmission used in the car was the 4L60E, which was itself an upgraded and revised version of the previous 4L60. However, the transmission was not beefed up for the power of the LT1, and transmission failures after 100,000 miles (160,000 km) were commonplace. A standard transmission was never available in the 94-96 the impala ss. However there is a growing trend to replace the 4L60-E transmission, with the T-56 (6 speed manual) from the camaro and firebird using aftermarket kits....

Ooooooh, methinks you could convert it to a stick and have fun again.

CarloSW2

[Big Dave]

If I keep it, it will get a T-56 or maybe a Tremec 6060.

[Christ]

Another thing you could work on is the whole manumatic idea, since it's a #x##E version.

I bet you if you shift the selector into the lowest gear, take off like a moron, foot to the floor, you won't hit redline. The TCU will automatically shift without your input (via the selector lever). That means you can manually control when the TCU sets shift points with switches, and you can probably manually control TC lockup as well.

If you're worried about the transmission dying, doing the mods will just kill it faster (in your mind) so you can swap to a manual sooner.

[roflwaffle]

With a 350 ya need to practically be idling down the freeway to end up in a decent part of your BSFC map. In order to get near 30mpg ya need to drop from ~1500rpm@55mph to ~1000rpm@55mph, and even then, you'll still only be at ~400g/kWh instead of the optimum around ~300g/kWh.