Since the po seemed to be trying to run it into the ground I would do a major service on it asap. Ie change all the fluids and filters.

At 236k you should also check and repack the wheel bearings.
Inspect the front flex disc for cracks or warping.
Shocks may be leaking as well

I'd run whatever octane the manual calls for.

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2006 CL500
1969 280SE
2023 Ram 1500
2026 Genesis GV70
2007 Tiara 3200