Songfacts®:

• Queen's drummer Roger Taylor wrote this song, sang on it and played drums on the track. Though it was dedicated to Queen roadie John Harris ("a boy racer to the end."), there was still something autobiographical in this car-as-a-metaphor-for-sex song. "I'm not obsessed," the Queen drummer told Mojo, "but I do love a good car."
• The engine noises on the recording of "I'm In Love With My Car" are authentic and come from the car Roger Taylor owned at the time. He described in a 1997 interview with Pop On The Line: "I remember my car at the time, because I think we've got the exhaust on the record, and that was a little Alfa Romeo. But I think it was more about people in general, for instance boy racers. In particular we had a sound guy/roadie at the time called Jonathan Harris, who was in love with his car, and that inspired that. I think he had a TR4, Triumph TR4."
• Roger Taylor loved the song, and demanded it to be the B-side to Freddie Mercury's "Bohemian Rhapsody" single - so much so that he apparently locked himself in a cupboard until Mercury agreed. Perhaps there was a good reason Taylor really wanted it to be the "Rhapsody" B-side - the song credit went completely to him, and when the single became a huge smash hit, he received almost equal royalties as Mercury did for "Rhapsody."
  
  This naturally rather annoyed the rest of the band! Songwriting credits and friction over royalties are a common reason why most bands break up. For this reason, Queen later in their career decided to give a collective co-writing credit for all songs, regardless of who contributed. This meant everyone got equal royalties for any singles/hits, which meant there was less friction with members more willing to let their songs/ideas be worked on - knowing they wouldn't lose any credit or royalty money in the process.
• There's a running gag in the Bohemian Rhapsody movie where Brian May complains about Roger Taylor getting "I'm In Love With My Car" on the B-side of "Bohemian Rhapsody." According to May, the tension was very real.
  
  "We were aware of the supreme injustice of 'I'm In Love With My Car' making as much money as Bohemian Rhapsody," May chuckled to Mojo magazine. "It was a real sticking point for the band and it's good we got through it. I think our sense of humor saved us. How long did it take me to get over it?... oh, quite a while."
• Roger Taylor sings:
  
  Told my girl I'll have to forget her.
  Rather buy me a new carburetor
  
  Asked whether his bandmates had embraced the song's premise, Taylor chuckled, "Brian was like, 'Is this a joke?' I said, 'Look at all those people out washing their cars on a Sunday morning, lavishing attention on them; they probably love their cars more than their wives.'"
  
  "I think it's a valid lyric," he added, "though obviously a bit tongue-in-cheek."