Yes. Its possible. Especially when the mesh doesn't have midside node. You can check it under mesh section of analysis. There are three options for midside node;
Go to Mesh->Defaults->Element Midside Nodes-> Program Controlled/Dropped/Kept
If you dont have any element or node number limit problem, you should activate the midside nodes (Kept).
So what's the problem? you might use 4 node element or 8 node element. based on your geometry and problem you may use different element types with various node number.
Yes. Its possible. Especially when the mesh doesn't have midside node. You can check it under mesh section of analysis. There are three options for midside node;
Go to Mesh->Defaults->Element Midside Nodes-> Program Controlled/Dropped/Kept
If you dont have any element or node number limit problem, you should activate the midside nodes (Kept).