10: Check Your Tires
Tires are one of the most overlooked parts of a car. According the Rubber Manufacturers Association (RMA), only one out of 10 drivers checks his or her tire pressure correctly, compared with almost seven out of 10 who wash their cars regularly [source: RMA]. But the truth is that an under-inflated, over-inflated, worn down or misaligned tire can be extremely dangerous, particularly in hot summer weather.
9: Change Oil and Oil Filter
Oil is the lifeblood of your car. It keeps hardworking engine parts running clean, smooth and cool. Most owner's manuals suggest that you change your oil and oil filter every 7,500 miles (12,070 kilometers). Oil change specialists suggest every 3,000 miles (4,828 kilometers) or three months. The fact is, most of us do a lot of heavy driving during the summer when an engine is more likely to overheat. So at least check your oil before you head out on that road trip with the family.
8: De-Winterize Your Car
If you haven't driven your car very much during the winter, or if you've had it in storage, then you need to check all of the fluid levels -- coolant, transmission,differential, power steering and brake fluid -- to make sure there weren't any leaks. You'll also want to change the oil, since oil gets thick and collects condensation if it sits in the engine all winter. If you haven't used your battery in a while, you might need a recharge or a replacement. It's also important to really clean the undercarriage of the car after a long winter, especially if you live in a snowy climate.
7: Check Hoses and Belts
The key to summer driving is keeping the engine cool. We're going to talk about the radiator and coolant soon, but first you need to check the hoses and belts. The hoses connected to the radiator help pump coolant to and from the engine block, and the belts run the fan that helps cool the system further [source: CBS News]. If the hoses crack or the belts snap, the radiator will quickly overheat, leaving you stranded.
6: Change the Air Filter
Over the winter, your car's air filter can get clogged with salt and other thick debris. A clogged air filter can really lower your fuel efficiency. Replacing a dirty or clogged air filter can improve gas mileage by as much as 10 percent
5: Replace Your Windshield Wipers
Winter can be tough on windshield wipers. Ice, snow, salt and extreme temperatures make cracks and tears in the rubber that lower the effectiveness of the wipers. If your wipers are leaving visible streaks or take several passes to clear away light rain, they need to be replaced.
4: Check Your Brakes
Brakes need to be replaced when the lining on your brake pad or brake shoe is worn down past the minimum thickness specified by the car manufacturer or state law [source: Yahoo! Autos]. You can have your brake linings checked at any normal service shop or at a brake specialist.
3: Check the Coolant and Radiator
Cars are designed to run hot, but there's a limit to how hot they should run. A combustion engine is most efficient at around 200 degrees Fahrenheit (93 degrees Celsius). But if an engine is allowed to get too hot, moving metal parts can actually start to melt and fuse together, causing a variety of internal problems for your engine -- and, you guessed it, a hefty repair bill.
2: Clean Your Battery
Wintertime is notorious for dead batteries and early morning jumpstarts. But the truth is that hot weather is even tougher on your battery. Summer heat can speed up the chemical reaction inside a battery, causing the battery to be overcharged [source: CBS News]. This can dramatically shorten the lifespan of your battery. Heat can also damage the battery by evaporating internal battery fluid [source: Car Care Council]. The best way to keep your battery running smoothly is to keep it clean.
1: Maintain Your Air Conditioning
The most common cause of a malfunctioning air conditioning unit is a low level of refrigerant. This could be caused buy a leak somewhere in the system. Since modern air conditioning systems are complicated creatures, it's best to have a professional check out the problem.
Tips courtesy of: http://auto.howstuffworks.com/car-driving-safety/accidents-hazardous-conditions/summer-car-maintenance10.htm