It has nothing to do with Mike's feelings; it's about gas prices in Timeful Warpland and how Elly can never catch a break.
Panel 1: We start out with Elly in the hovercar fumbling through her purse and frantically saying "I think I have a credit card....no, wait, maybe I have a check..." This is, of course, because she doesn't know what wallets are and how they can be kept in purses to avoid constantly going through stuff like this.
Panel 2: She meekly asks the service station attendant if she can get $1.80 of regular. The reason is that a buck eighty is all the small change she's got on her.
Panel 3: With her face frozen in the Bug-Eyed Glare of Existential Horror, she asks herself why the car only runs out of gas when she drives it.
Summary: The "answer", of course, is that she's fairly disorganized and cannot budget well enough to both buy groceries and top up the tank on the amount of money Scrooge, er, uh, John hands her. I mean, even back in 1980, a buck eighty of regular wouldn't have gotten her very far. It's a collective stupid that mostly burns Elly. In my opinion, John should remember that Elly's default state of mind is that of blind panic and act accordingly.