RepairPal Certified shops can diagnose and repair your 1998 Nissan Altima. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Here is a link to an interesting antifreeze / coolant recommendation chart:
https://images.oreillyauto.com/uploads/pdf/ad/SD_672%20AFZ%20Comparison%20Chart-1.pdf
Check out the chart then you’ll know what should have been used.