l was told l need to use premium for it, and now someone else tells me that only the older saab models need premium and l can use regular. Is it okay to use regular, or should l stick to premium?

Depending on which SAAB 9-5 u have, u can use Octane 91 with some loss in performance but Octane 95 is recommended unless it is an AERO where Octane 98 is recommended but can be driven with Octane 95 with some loss in performance. Do not use Octane 91 in an AERO model. By older models most of the time it is mea not for pre 1998 models.
PS
When u get low performance from the engine & u r not used to this performance level, u press more on the accelerator & u actually use more gas. In addition, SAAB is giving u max & min Octane # to use. Lower Octane # will cause other problems like inefficient burning, carbon deposits etc & later all will blame SAAB. Please stay within acceptable octanes as recommended. The computer will ofcourse adjust but then only upto a certain level & then u will start to get check engine light.

l am sure you could use regular. Check in the back of the owners manual, most newer saabs only require 87 octane or higher.

With gas prices the way they are, l would just go with regular (87). It is very unlikely that it will hurt your car or cause any noticable changes.

Trust me. Through experience you can use any grade 87 and up in any model and year of the 9-5. The engine computer is very advanced and detects knocking and pinging right away and retards the timing so it will stop knocking. You cannot damage the engine by putting in lower octane fuel, you will just notice a loss of power, particularly in boost. Saab simply recommends the high octanes for maximum efficiency and power.