Which brings up a big difference between synthetics and conventional mineral-based oils: Conventional oils can be freely mixed. Other types of engines, particularly turbines, don’t use leaded aviation gas and can use synthetic oils. They’re not used in piston-aircraft engines because the lead from aviation gas can interact with the oil to produce sludge, which needs to be removed by changing the oil. Most variable-viscosity oils are built on natural mineral base oils, but there also are fully synthetic lubricating oils that offer several advantages over mineral oils (among other things, longer oil change intervals). ![]() At low temperatures, they have no real effect on the overall viscosity of the oil, but as the temperature rises, the yarn (actually polymers, basically, plastics) unroll, and as they do so, the oil thickens. Variable viscosity oils start with a low-viscosity base oil (for a 10W-40, starting with an SAE 10 base oil) with viscosity modifiers (VMs) added. On the other hand, the SAE 10 oil that’s good for starting won’t do a good job of protecting your engine on a long cross-country. That’s ideal for pilots who live in the snow belt you don’t want to try starting the engine at below-freezing temperatures with an SAE 40 oil. A 10W-40 oil is an oil that acts like SAE 10 at room temperature, but like SAE 40 at operating temperature. There also are variable-viscosity oils, which are thin at low temperatures but thicken at high temperatures. During break-in, that can actually be a good thing! Ben Visser, a former AeroShell lubrication expert, told me that using straight mineral oil for break-in “goes back to the old hard chrome used to bring cylinders into specification, where you had to actually wear down the parts-the particles worn off work as a lapping compound.” ![]() Straight mineral oil is pretty much what comes from a refinery, and it’s a good lubricant, but it won’t keep your engine clean. Most piston aircraft and engine manufacturers approve two major types of oil for use: straight mineral oil and ashless-dispersant (AD) oil. More likely, it will provide general guidance, or refer to a service bulletin (SB) or service instruction (SI) from the engine manufacturer. But first, a warning: Before changing the oil in your airplane, check the owner’s manual! It may specify particular oils. ![]() I’m going to start with the traditional horizontally opposed piston engines used in most GA airplanes, and then move on to more exotic alternatives. Which type to use also depends on what kind of engine you have and what kind of flying you do. If you own an airplane, using the right oil and knowing when change it are some of the most significant things you can do to keep an engine running to (or beyond) the manufacturer’s recommended TBO.įiguring out which oil to use requires understanding a few concepts-notably, the type of oil (straight mineral, ashless-dispersant or synthetic), viscosity and additives.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |