Filter changes are probably the easiest job in Car Mechanic Simulator 2016. You've got Fuel Filters, for which there is almost no variety, Air Filters for which there is some variety, and Oil Filters, for which there is a bit more variety. Figuring out where these may be hiding on some special vehicles may pose a bit of a challenge at first, but for the most part it's pretty straight forward.
Changing Oil Filters is pretty simple. The only deviant is the Maluch, which has the Oil Filter in an odd location. It also looks completely different than the other filters. On all the other vehicles the oil filter looks roughly like a sauce jar and is color coded for the engine type it fits.
Fuel Filters pretty much work the same as oil filters. They are actually easier, since there are only two types of filters. There is one for the Maluch and one for everything else.
Air filters do have some variety, however. You've got two types of round ones, a rectangular one, a side-draft one, and one for the Maluch. These screenshots should show you what to look for to make your life easier. Also check the notes that appear under each screenshot for more information.
One thing to double check when the repair order says to change the oil filter: it may not say to change the engine oil as well. Yeah, I know. Ask a mechanic about that one.
Also keep in mind that filters cannot be repaired and must be replaced with new ones.
To help you learn the diagnostics side of Car Mechanic Simulator 2015 as quickly and easily as possible, I have created a few short but comprehensive guides covering each problem category. For a complete listing of these guides, check here:
Diagnostics & Repairs - Car Mechanic Simulator 2015
If you are looking to learn about the early and mid-stages of the game, you may find these pages of interest:
Your Garage, Tools, Tests, & Upgrades, Jobs & Job Management
And if you are wonding what awaits beyond and where the real cash is hiding, check out this link:
Rebuilding Guide - Car Mechanic Simulator 2015