A metal detector. oil filter and shut off valve emerge from basement filler pipe and vent are not right next to wall outside you cannot find the oil tank inside
No oil tank inside the house.
If you live on an old farm or a residence that housed a lot of motor vehicles, there may be an oil tank buried in the ground that was used to fuel machines. These tanks can corrode over time and leech unwanted toxins into the groundwater, or one may be taking up space where you'd like to build. Either way, you can safely remove an in-ground oil tank with a few tools from the hardware store and one or two strong friends. it would be around 40 feet in ground
No tank inside, filler neck in the yard.
The easiest way to tell if an oil tank in buried on the the property is the presence of a vent and/or filler tube coming out of the ground on the exterior. They are both about 2" wide. Sometimes these are cut off so you can look in the basement near the furnace or boiler. You may see two 1/4" copper tubes coming through the wall or out of the floor. These are the oil supply lines. They can give you a clue where to look on the exterior. This is a good article on the subject.
Filler neck and vent pipe in the yard is one clue.
The easiest way is looking for oil pipes coming through your walls - theyare hard to miss.
Unexplained pipes going through the basement wall. Patchy or yellow grass above tank outside.
oil
maybe
A "16 ft tank" does not tell us it's volume.
it depends if its a older bike you may have to put premix in (mix of oil and gas) in the tank if its a newer bike it will have oil injection and you only have to put oil in the oil tank and it mixes with gas in the carb, in any case try to get a manual for the bike in question it will tell you what to do
petroleum is usually taken form the ground by drilling a narrow hole into a petroleum deposit and simply pumping out the oil