Premium unleaded gas is something I ** NEVER ** put in it. NEVER. Not even mid-grade unleaded. Well, maybe the first week, just for comparison. Notice that only the manual indicates premium unleaded. The fuel door and the gas gauge only say "unleaded fuel only". I have even on numerous occasions, used Sunoco's now-discontinued "Economy" grade (86 octane) with absolutely NO noticeable difference in performance. Lest there be a chorus of "But...but...but..." from the technologically inclined, I will bring up the only "but" that really counts: my '89 went over 256,000 miles on exclusively 87 octane. It always ran perfect, always beat the other car in the stoplight grand prix, and did not have one thing done to the engine. Not a head gasket, nothing.
And my current '91 MI16 is just as happy on cheap ol' 87 octane, too.
On to some other things.
Radio antennas: I never had an electirc antenna that lasted more than two years, no matter how often I cleaned, lubricated, etc. All the way back to our '85 505 Turbo. Two year lifespan. The Radio Shack electric antenna fits reasonably well (about $40), although you'll have to cut and solder some wires because the connector is different. Not all that difficult to the electrically-inclined.
Radiator fan: If one of yours seizes up, as mine did, try to find one from a 505 for cheap. The one I got fit the three-bolt mounting with the addition of some spacers. Only it fit backwards. Reverse the wiring to make it spin in the correct direction. Danger!!! The 505 fan is now outside the safety of the shroud. Caution is indicated.
Suspension: Wheel bearings, rubber bushings, etc. lasted over 200,000 miles before requiring replacement.
Shame that the transmission was the downfall of the '89. I couldn't justify the expense on a car that was finally showing a little wear. I was aiming for 300,000.