What is the logic between 12v battery and lower MPG?

Alas even that isn't fool-proof.......because sometimes the fool running the test stops it after only a few seconds and pronounces it "good".
The test load needs to be left on for at least 10 to 15 seconds as specified in the book for the tester.......which likely is long gone.
It will always identify a battery that is REALLY sick; marginal ones, not so often.

 

Yep...I got one an old school toaster. Leave it on just till the resistor starts a stinkin'. 10-15 seconds and watch if the needle nose dives. Tells me all I need to know about the patient. You can buy them real cheap on Ebay like $15. I paid $5 for mine. It does not lie.

Works really good as surface charge remover.

This one:

 

You will need to shim the rears to fix the toe and the fronts should have a slight toe in to avoid "wandering" at highway speeds. Camber should not directly affect MPG.

JeffD

 

Don’t you mean toe out? But I don’t think it should wander with toe at zero.

 

No, toe out would result in unstable handling.

Imagine trying to ski with the tips pointed out.

 

If the alignment is within spec then there is no obvious error. However if the last alignment was recently done, you could go back and ask for the front toe to be set exactly to zero. Maybe the garage would take care of that without charge to you.