Keeping the same model and age of tires on the same axle will help minimize some issues. Your range will probably take a hit.I have 2018 plug in hybrid 28k miles front tires need to be replaced rear tires still good All OEM Michelin energy savers Can I put two new Continental Pure Grip on rear and rotate the OEM tires to the front
Replacing all four at the same time will always be the safest choice. The trick is to rotate the tires regularly so they wear at the same rate, so that replacing them all at the same time makes sense. Replacing tires that still have a lot of unused tread on them is a difficult decision, especially when funds are tight.You should get all 4 tires the same and in the same condition (new).
Running 2 different sets will change handling as well as wear.
I am also replacing my original Michelin set with run flat (RFT) tires so that I don't have to worry about being stranded on the side of the road...