In the 1970s, the word "lube" may have had a sexual connotation, but not as inescapably as it does now. The risibility of words comes and goes. Consider the ejaculating characters in the Sherlock Holmes stories. Or consider Lady Macbeth's speech: "Come, thick night,/And pall thee in the dunnest smoke of hell,/That my keen knife see not the wound it makes,/Nor heaven peep through the blanket of the dark,/To cry 'Hold, hold!'"
In Dr. Johnson's day, "dun," "knife," "peep," and "blanket" all seemed ludicrous in the context of a solemn tragedy, just as "lube" seems ludicrous in the context of ... a solemn episode of "SuperFriends"?
Why does Batman command Robin to use Bat-lube? They are escaping into the air, courtesy of their Bat-cables, when Solomon Grundy suddenly grabs their legs. They each press a button on their respective utility belts and an oily substance squirts out, which runs down their legs (!) and causes Grundy to lose his grip on them.
Oh, come on. Did he really say "Bat-lube"? Here's how the lines go exactly:
BATMAN: Quick, Robin, the Bat-cables!
ROBIN: He's got us, Batman!
BATMAN: But not for long, Robin. Use your Bat-lube!