You can use different lawn fertilizers for spring, summer and autumn, or use the same type all three seasons. I use just one type all seasons except winter. I don't use feed 'n weed because it will kill my flowers and vegetables. For all liquid fertilizers, you need to read the instructions carefully. Some are ready-to-use. Some must be diluted before use. As for the time of patching the lawn, there is really no strict temperature requirement, although seeds germinate better at a lower temperature. I sometimes sow grass seeds in the middle of summer. They seem to do just fine.