Viscosity is the measure of how well an oil flows. Thicker oils have higher viscosity and protect moving parts within engines and other equipment better than thinner oils with lower viscosity. At low temperatures, oil flows much slower. If you use a high viscosity oil in an engine in cold weather, oil may not be able to reach and lubricate some important moving parts. Bio-diesel fuels made from used vegetable oils or different types of oils all have different viscosities and properties that have different effects on engines. Diesel engines are generally very forgiving when it comes to oil viscosity at normal temperatures. However, if you are running your diesel engine on homemade bio-fuels, it is important to be able to measure the viscosity of the oils you use to make it. You can make your own homemade oil viscosimeter for two to three dollars.
Cut the bottom off the empty plastic bottle. Use sandpaper or a small file to smooth and round out the ends of a one-inch metal tube. You don't want any burrs or jagged edges on the metal tube. Use old brake-fluid lines if they are available to you. They are the perfect size.
Drill a small hole in the top of the cap and squeeze the metal tube tightly through the hole.
Push the metal tube half-way through the hole in the screw-on top.
Drill a hole about the same size as the screw-on bottle top into one end of the flat wood. The screw-on-top of the plastic bottle must fit into the hole in the wood tightly with the bottle top on the bottle.
Screw the top tightly onto the plastic bottle. Use the permanent marker to clearly mark a line on the plastic bottle about 2 inches below the bottom of the cap. This line will be the "finish line."
Turn the bottle bottom-side up. Plug the metal tube with your finger while pouring 3/4 quart of water into the bottle. Put a bold line at the level of the water with the permanent marker. This will be known as the "starting" line. Before you empty the water from the bottle, note any leaks. If there is a leak, you can fill in the leaking holes from the tubing and cap with rubber cement or glue a very small O-ring around the end of the tube.
Push the bottle top into the hole in the board so that the bottle stands perpendicular to the board. Put the board on a tabletop with the bottle end of the board extending over the edge of the tabletop. Put a heavy weight on the other end of the board. This can be bricks or a heavy rock. You can now begin measuring viscosities of oil.
Remove any contaminants from the oil samples you are testing with coffee filters or cheesecloth. Your oil samples must be clean to get accurate results from the tester.
Test all oil samples at the same temperature. Colder temperatures will slow down the "run" time of the oil samples. Room temperatures will give the most consistent results.
Fill the plastic bottle of the tester with the oil sample until the oil level is above the "start line" marked on the bottle.
Put an open-mouthed jar or container on the floor or on a stool under the viscosimeter to catch the oil as it runs through the metal tube out of the tester.
To start the device, hold your finger on the opening of the metal tube while you pour the oil into the plastic bottle and then release your finger to start the flow. Start your stop watch at the moment you release your finger and be ready to stop it the moment the oil reaches the "finish" line marked on the bottle.
