What additives can I use to put in my gas tank of a vehicle which is not being used?
I assume you mean to help keep the fuel fresh in which case fuel stabilizer is what you want - Stabil is a common brand. I have started to use Sea Foam just b/c I usually have some around for other purposes as well.
If it is being stored over a couple of months, then a fuel stabilizer is a good idea. Follow the directions on the container. Premium is no advantage. It may also be a good idea to fill the tank before storing it as that will reduce the chance of moisture.
Remember if you are storing a car, you can usually cancel the collision part of your insurance as it will not be driven. Remember to start it back up before you drive it.
Fuel stabilizer such as STAYBIL is waht I use. Remember that it must be added to good gas. It will not make bad gas good again. It’s now in my 79 c10 p/u which hasn’t been driven since August and probably won’t get driven till March. Also use Staybil in the fuel you store for your ATVs, chain saws, weed eaters etc.