Can a weak battery cause poor gas mileage?

Question

My battery was low and when I replaced it the gas mileage seemed to get better. I'm not sure ,but I was filling up almost every two days and now I fill up once a week. I drive just as far as I did before.

I'm extending this one because the answers are pretty varied. I'd like to see what other things people can come up with.

Answer 1

no. After the car has been started, most of the electric components run off your alternator rather than your battery. Because the alternator runs off a belt that connected to the crank it will always run as long as the car is running. If the alternator bearing are worn out it would produce more friction so the engine would need to work harder to crank everything. Even tho this is true, most poor gas mileage will not be related to the battery nor alternator. Look at things like a tune-up(changing the sparkplugs, ignition wires, distributer, fuel filter, etc..)
check the tire pressure, lose the extra weight in your car so the car has less to lug around.

Answer 2

Although it could cause some difference in gas mileage, the effect wouldn't be that noticable. That seems like a pretty large jump. Have you by chance stopped using your A/C as much lately? That usually makes the biggest difference in MPG.

Answer 3

it si true your alternator would be working full time and would therefore make the engine work harder. with a 4 cyl engine it COULD make a differance. this being the case have you noticed worse gas mileage at night when the alternator works really hard all the time?

Answer 4

Yes it can if the battery is week it puts a strane on the altinator which draws down the rest of the cars functions.

Answer 5

Yes, if it is in a Dodge Durango.

12 mpg. Yikes!

Answer 6

No, but things that can are low tire pressure, needing tune up, excess weight.

Answer 7

With out getting into technicalities, in short....NO!!

Answer 8

no way jose

Answer 9

no

Answer 10

No.