Poofy Goof Rant-O-Matic

I have a 1991 subaru loyale. it's only a couple hundred miles away from 200,000, and has become my "bucket" workhorse vehicle. as it has aged, various problems have cropped up, mostly electrical, but one long term problem that's been getting worse has been the engine timing. it had been pinging under load, which I offset by using 89 and 92 octane gas in it, but under load even 89 octane had started to ping, and with gas prices close to 3.50/gallon for the 92, I've been investigating the feasability of getting it to run on cheaper 87.