Hello! I have just bought myself a 1991 rx-7 and am looking to keep it in the best condition possible. The previous owner recommended premixing oil into the fuel, but I don't know exactly what premix to use and the correct steps to go about it. Also, are there any special maintenance schedules I should be practicing (other than the basic oil change and stuff)? It is also revving at 3000-4000 rpms when I start it up, is this normal? It only lasts for about 10-15 seconds before going back to normal and idling at 900. I am 18 and am trying to learn to work on cars, so please excuse some lack of knowledge.

Edit: Okay so I parked the car in a parking spot when I saw a water-substance leak underneath it. I popped the hood, and it looks like a hose connected to the charcoal vapor canister got cut. The hose goes under the passenger firewall. What should I do to fix it??

There are some photos below, there is a red circle around the cut hose.