Oil: While the car is cool, lift the hood and pull out the dipstick, the rod that measures the oil level. (Trouble finding it? Check the car manual.) Wipe the stick with a rag, reinsert it, and pull it out again. If the oil level doesn’t fall within the zone marked with crosshatches, add a quart. “You can end up with severe damage if your engine is starved of oil,” says Michael Calkins, an auto-repair manager at AAA. Be sure to use the type recommended in the manual (or see the maker’s website). A car is made to run on a certain oil, and “using the wrong kind can cause increased engine wear,” says Calkins. Store a quart in the trunk.
Radiator: Under the hood, you’ll see a transparent plastic tank (attached to the radiator by a hose) that’s marked with two lines. If the fluid falls below the lower line, top it off. Again, make sure you use the proper type of fluid or you run the risk of damaging the engine.