Continuing on that age thing for McQueen-

Lightning McQueen is in his mid-forties - most likely past 45. The age cap for Nascar retiring is at least 45, and McQueen is seen as an old-timer. Therefore, he must be around that age otherwise everyone wouldn't see him as so old. This also explains why McQueen is like "I'm not even that old bOi like what"

I looked too deep into this lol

I just assume all that though. In the first movie, Lightning is probably 16 or 17 (age of consent to join Nascar back when Cars first came out) considering that he's a rookie. I'm also assuming he's 24-26 in the second movie (despite that movie sucking so much that it wasn't mentioned at all in the third movie).