Mine is purposeful and I use it every day. I am into cars and can pretty much do whatever I need to in order to fix one or customize it to my needs. I do everything from engines and transmissions to welding up rust holes and all my own paint and body work too. I even do my own wiring and am trying to learn how to do upholstery. Needless to say I have had other obsessions within the automotive sphere including hypermiling, drag racing and the cars of the former Soviet block (GAZ, UAZ, IZH, ZAZ, Trabant, Lada, Zastava, FSO, etc.)
I have obsessed over weirder things though, like nuclear war and cold war civil defense shelters. I've even done a little bit of "prepping", like putting away some canned goods and trying to grow a garden. It turns out that gardening is a lot harder than it looks. Sadly, my garden died before I could get much of a harvest. I am probably going to try again this fall so that I can learn from my mistakes.
So yes, my special interests have been quite boring and practical. This is probably because I tend to be boring and practical and generally try to learn things that make me more self sufficient.
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Uncertain of diagnosis, either ADHD or Aspergers.
Aspie quiz: 143/200 AS, 81/200 NT; AQ 43; "eyes" 17/39, EQ/SQ 21/51 BAPQ: Autistic/BAP- You scored 92 aloof, 111 rigid and 103 pragmatic