My junkyard battery works great in every respect- except MPG.

I'm getting mid 30's - my tires are lousy, i'm putting off getting fresh tires until i deal with the rear control arm issue.

All the battery performance indicators i am aware of show a good battery-

- the SOC indicator cycles through the whole range
- i neverer have battery recal.
- the car starts on the main battery pack after sitting for several days in fairly cold weather.

No IMA or Check Engine lights.

As for the tires, - the car came iwth 80K miles and lousy tires.

I got a gooed deal on a pristine set of 195/60's - slightly smaller than required. - my corrected mileage with the smaller tires was a solid 41 mpg with no real effort on my part.

THen the tires started wearing out and i learned about the rear control arm issue. Right now I have 195/65s in front and the smaller tires on the back. the front tires rumble (having been rotated from the rear)

So, could the tire issue account for 6mpg?