Changed my Battery, increased MPG by 10%

[Zalittle]

I know this sounds like hype, but I bought a 1997 Chevy Malibu with a V6 from a local church where I live in the mountains on the Cumberland Plateau in Tennessee.
When I started driving the car after basic tuning, I was getting 27 MPG to and from work. 2 weeks ago the battery died. I checked the date on battery and it was 8 years old. Not bad for battery life at all.
I put the best battery I could find for the money and got the highest amp output battery I could find.
The strange thing is my MPG went to 30.3. I have tried to figure this out and talked to various levels of mechanics and friends.
The only thing we can figure is the electronic system sensors, fuel pump, and the like were not getting proper voltage and amperage to run at 100% efficiency.
Any Idea's?

[theholycow]

Perhaps a worn-out battery can lose efficiency, wasting more energy than a new one does during charge/discharge. If so, the alternator would have to do extra work, which of course is more drag on the engine.

However, 10% sounds quite severe. Do you have a fuel log with well-controlled accurate fill habits and a consistent route to rule out as many other variables as possible?

[add|ct]

Staying on topic, I've wondered this for the VX I drive.

It had a Die Hard battery, but it's not reverse in the position of the Pos/Neg posts. The positive is positioned closer to the passenger side, while the negative is closer to the driver's side. This vehicle spec's for a 51r, IIRC. Would that make a difference?

For the record, the battery has been drained "completely" or close to it once, and near completely a 2nd time, in the last 2 years. Ran a slow charge all night twice after each incident. Added one engine ground(4 gauge wire), and cleaned up the others. The alternator was inspected by a Honda Master Tech and was within spec.

Still, I wonder if a new battery would improve MPG any or idling conditions.

[bowtieguy]

2 weeks ago? i wouldn't base this increase on anything until you've had several fills to confirm. might just be warmer weather, you adapting to the car, or just a short fill...among many other things. keep us posted!

[theholycow]

Come to think of it, could be the gas station switched from winter blend to summer blend...

[VX_Arky]

Originally Posted by theholycow

Come to think of it, could be the gas station switched from winter blend to summer blend...

My thoughts exactly while reading this thread.

[FrugalFloyd]

Originally Posted by add|ct

Staying on topic, I've wondered this for the VX I drive.

It had a Die Hard battery, but it's not reverse in the position of the Pos/Neg posts. The positive is positioned closer to the passenger side, while the negative is closer to the driver's side. This vehicle spec's for a 51r, IIRC. Would that make a difference?

No, it shouldn't make a difference. Nor should a new battery.

[bowtieguy]

Originally Posted by SentraSE-R

No, it shouldn't make a difference. Nor should a new battery.

actually it can...my wife's camaro had some sensor issues during a low battery situation. it was confirmed by a data stream read out before and after a new battery install. apparently the computer was not getting enough "juice" to read, communicate, and diagnose accurately.

[Ford Man]

I agree that a worn/old battery could decrease mileage, because the electrical system is being over worked trying to recharge a battery that's no longer maintaining the correct cranking amps. I know for a fact that I've had batteries that when they got older the lights would get dim during low speed idle conditions.

[theclencher]

OEM battery in my '94 Ford still going strong! If it ever goes bad I'll shop for an identical Motorcraft battery- hopefully they're still making them just like that.