By 1968, Avis' powerfully blunt "We try harder" campaign had been effectively checkmated by Hertz, forcing Avis' ad agency, Doyle Dane Bernbach, to settle for a softer approach:
"Just one of 47 bugs we're trying to get rid of at Avis," the ad says. In previous ads, Avis had never flinched at admitting responsibility for any problems; now the ads were creating humorous culprits to take the blame; the change in attitude couldn't be more stark.
And it probably didn't help that Essolube that run essentially the same campaign three decades earlier:
(Lots of other Dr. Suess-illustrated and concepted ads here.)
UPDATE 4:30 P.M.: Apparently, Shell also beat Avis in discovering its own engine-beastie in 1952. And judging by its devilish appearance, this one seems far more malevolent in nature: