It s not unreasonable to simply assume that after about 40,000 miles, the shocks and struts are worn out and should be replaced. However, a lot depends on how rough the roads are in your neighborhood. Struts and shocks wear out and affect handling and tire wear. Peculiar tire wear can often be traced to a worn strut or shock. Check shocks and struts, or have them checked, every 15,000 miles, or so.
Oil leaking out of a shock or strut indicates a part that needs to be replaced.
How they work is checked by standing on the bumper at each of the four corners of the car in turn, and bouncing up and down to simulate a bumpy road, and leaping off at the lowest point of downward travel. Get the car moving up and down pretty good. This test will be a demonstration event in the next Summer Olympics to be held in Moose By-product, Arkansas. There s nothing to do concerning maintenance of the exhaust components such as mufflers and pipes. They ve been included here because they often fail, and it s a good idea to keep track of how much service the replacements provide.