Poor battery connection = bad mpg??

[webbch]

Last weekend I was replacing the contacts in my starter solenoid because I was having cold start symptoms exactly consistent with worn contacts on the starter solenoid as discussed on this forum. For some reason, before even thinking about where the starter was, I removed the airbox and battery for access reasons, since that's typically how most of my repairs in the past on this van have started out, and it only takes a couple of moments.

So I finish up replacing the solenoid contacts, kicking myself for removing the airbox (technically the air inlet resonator I believe) and battery as it was completely unnecessary for this repair. I go to re-attach the positive battery terminal, and as I tighten it up, it breaks. Root cause is that the positive terminal on my battery is slightly larger than the negative terminal, and the battery cable had been replaced before with the incorrect size (I'll admit, that was my mistake from a year ago ). After a couple of open/close cycles, it fatigued and broke. So I ran down to the parts store and got the correct size battery cable this time. After installing it, I had a battery terminal brush laying around and used it to clean/rough up the terminals before re-installing.

That was the only work performed. We haven't changed our driving patterns at all (typically drive about 450 miles/week), and there's been no significant change in weather patterns, yet we're suddenly getting 2+ mpg better than before. We used to only get about 17.5 mpg, and immediately after this work, we're getting 19.5-21 mpg.

The best part is, the grand total for all the work performed was $12.93 ($4.86 for solenoid contacts, $8.07 for battery cable). At our rate of driving, this repair will pay for itself in about 2 weeks in fuel savings, in addition to the benefit of no more cold start problems. Of course, having the tools and supplies on hand to do the job was pretty nice.

I have no explanation for this other than a better battery connection is responsible. I never would've thought that MPG would be significantly effected with no other driveability symptoms present...