This might have been already added, but did want to voice additional assistance; if your lawn mower is a two-stroke engine, make sure to use two-stroke oil in combination with the gasoline as recommended by the manufacturer. Do not use regular lawn mower oil in two-stroke engines, or the other way around. Do not use automotive oil in your lawn mower or in a two-stroke engine - the additives and detergents in the automotive oil are not healthy for your lawn mower. Look for oils labelled as acceptable for service SF, SG, SH, or SJ. Oil additives are also important and there are plenty of bottles of oil additives on the shelves of big box stores and automotive warehouse, but don't be tempted to add them to your lawn mower. These additives are only helpful in large engines, they will only harm small lawn mower engines. Hope this helps!