Valve oil is essential for the proper functioning of a trumpet and is used to lubricate the inner workings of the pistons that move when the trumpet's keys are pressed. While valve oil is sold at any instrumental music store, it comes in different formulations. If you can't find one that suits you, or if you're just looking to save a little cash, you can mix your own. Play with the ratio of ingredients for a thicker or thinner oil.
Add a couple drops of scent oil to the bottom of the bottle. Add enough lamp oil to this to coat the bottom of the bottle, then swish the mixture around to combine the two oils. Start by using less scent oil than you think you'll need (if any); you can always add more later, but you can't remove it.
Fill the bottle three-quarters of the way with lamp oil. For the purposes of filling, measure the "top" of the bottle as being about 1/2 inch below the highest point you could fill to leave a little space for mixing and to prevent overflowing upon opening. If necessary, mark this spot with a permanent marker.
Finish filling the bottle with sewing machine oil. Add enough to reach the fill point you've designated.
Shake the bottle. Cap the bottle, then give it three or four vigorous shakes to mix the three oils.
Check the level of the smell and adjust. Give the bottle a sniff to see if you like it; bear in mind that when you use the oil, you'll want the smell to be faint, or the smell on the valves may be overwhelming to you and others.