Here are some common noises and what they mean:

Squeal — A shrill, sharp noise, usually related to engine speed:

Loose or worn power steering, fan or air conditioning belt.

Click — A slight sharp noise, related to either engine speed or vehicle speed:

Loose wheel cover.
Loose or bent fan blade.
Stuck valve lifter or low engine oil.

Screech — A high-pitched, piercing metallic sound; usually occurs while the vehicle is in motion:

Caused by brake wear indicators to let you know it’s time for maintenance.

Rumble — a low-pitched rhythmic sound.

Defective exhaust pipe, converter or muffler.
Worn universal joint or other drive-line component.

Ping — A high-pitched metallic tapping sound, related to engine speed:

Usually caused by using gas with a lower octane rating than recommended. Check your owner’s manual for the proper octane rating. If the problem persists, engine ignition timing could be at fault.

Heavy Knock — A rhythmic pounding sound:

Worn crankshaft or connecting rod bearings.
Loose transmission torque converter.

Clunk — A random thumping sound:

Loose shock absorber or other suspension component.
Loose exhaust pipe or muffler.

from http://www.consumer.ftc.gov/articles/0211-auto-repair-basics

The more you know about your vehicle, the more likely you’ll be able to head off repair problems. You can detect many common vehicle problems by using your senses: eyeballing the area around your vehicle, listening for strange noises, sensing a difference in the way your vehicle handles, or even noticing unusual odors.

Cold weather and winter driving conditions can reduce your fuel economy significantly.

Fuel economy tests show that, in short-trip city driving, a conventional gasoline car’s gas mileage is about 12% lower at 20°F than it would be at 77°F. It can drop as much as 22% for very short trips (3 to 4 miles).

The effect on hybrids is worse. Their fuel economy can drop about 31% to 34% under these conditions.

Why is winter fuel economy lower?

Cold weather affects your vehicle in more ways than you might expect:

• Engine and transmission friction increases in cold temperatures due to cold engine oil and other drive-line fluids.
• It takes longer for your engine to reach its most fuel-efficient temperature. This affects shorter trips more, since your car spends more of your trip at less-than-optimal temperatures.
• Heated seats, window defrosters, and heater fans use additional power.
• Warming up your vehicle before you start your trip lowers your fuel economy—idling gets 0 miles per gallon.
• Colder air is denser, increasing aerodynamic drag on your vehicle, especially at highway speeds.
• Tire pressure decreases in colder temperatures, increasing rolling resistance.
• Winter grades of gasoline can have slightly less energy per gallon than summer blends.
• Battery performance decreases in cold weather, making it harder for your alternator to keep your battery charged. This also affects the performance of the regenerative braking system on hybrids.

more at http://www.fueleconomy.gov/feg/coldweather.shtml

The more you know about your vehicle, the more likely you’ll be able to head off repair problems. You can detect many common vehicle problems by using your senses: eyeballing the area around your vehicle, listening for strange noises, sensing a difference in the way your vehicle handles, or even noticing unusual odors.

Looks Like Trouble

Small stains or an occasional drop of fluid under your vehicle may not mean much. But wet spots deserve attention; check puddles immediately.

You can identify fluids by their color and consistency:

• Yellowish green, pastel blue or florescent orange colors indicate an overheated engine or an antifreeze leak caused by a bad hose, water pump or leaking radiator.
• A dark brown or black oily fluid means the engine is leaking oil. A bad seal or gasket could cause the leak.
• A red oily spot indicates a transmission or power-steering fluid leak.
• A puddle of clear water usually is no problem. It may be normal condensation from your vehicle’s air conditioner.

from http://www.consumer.ftc.gov/articles/0211-auto-repair-basics

What should I look for when choosing an auto repair shop?

Ask for recommendations from friends, family, and other people you trust. Look for a repair shop before you need one to avoid being rushed into a last-minute decision. Shop around by phone and online for the best deal, and compare warranty policies on repairs. Ask to see current licenses if state or local law requires repair shops to be licensed or registered. Also, your state Attorney General’s office or local consumer protection agency may know whether there’s a record of complaints about a particular repair shop. Make sure the shop will honor your vehicle’s warranty.

How to Choose a Technician

Is one technician better than another? Look for shops that display various certifications — like an Automotive Service Excellence seal. Certification indicates that some or all of the technicians meet basic standards of knowledge and competence in specific technical areas. Make sure the certifications are current, but remember that certification alone is no guarantee of good or honest work. Ask if the technician or shop has experience working on the same make or model vehicle as yours.

from http://www.consumer.ftc.gov/articles/0211-auto-repair-basics

Our gas mileage tips can help you reduce the amount of gas you use. If you are already following these tips, you are probably getting the best gas mileage your car can deliver.

Keep Your Engine Properly Tuned

Fixing a car that is noticeably out of tune or has failed an emissions test can improve its gas mileage by an average of 4%, though results vary based on the kind of repair and how well it is done.

Fixing a serious maintenance problem, such as a faulty oxygen sensor, can improve your mileage by as much as 40%.1
Fuel Economy Benefit: 4%
Equivalent Gasoline Savings: $0.11/gallon

Keep Tires Properly Inflated

You can improve your gas mileage by up to 3.3% by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by 0.3% for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer.1

The proper tire pressure for your vehicle is usually found on a sticker in the driver’s side door jamb or the glove box and in your owner’s manual. Do not use the maximum pressure printed on the tire’s sidewall.
Fuel Economy Benefit: Up to 3%
Equivalent Gasoline Savings: Up to $0.08/gallon

Use the Recommended Grade of Motor Oil

You can improve your gas mileage by 1%–2% by using the manufacturer’s recommended grade of motor oil. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1%–2%. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1%–1.5%. Also, look for motor oil that says “Energy Conserving” on the API performance symbol to be sure it contains friction-reducing additives.
Fuel Economy Benefit: 1%–2%
Equivalent Gasoline Savings: $0.03–$0.05/gallon

Replacing a Clogged Air Filter on Modern Cars Improves Performance but Not MPG

Replacing a clogged air filter on vehicles with fuel-injected, computer-controlled gasoline engines—such as those manufactured from the early 1980s to the present—or diesel engines does not improve fuel economy, but it can improve acceleration.

Replacing a clogged air filter on an older vehicle with a carbureted engine can improve both fuel economy and acceleration by a few percent under normal replacement conditions.

…more at http://www.fueleconomy.gov/feg/maintain.jsp

Hot weather can actually increase your fuel economy. Your engine warms up to an efficient temperature faster; summer grades of gasoline can have slightly more energy; and warm air causes less aerodynamic drag than cold air.

However, keeping passengers comfortable in hot weather by rolling down the windows or using the air conditioning (AC) can reduce fuel economy.

Running your car’s air conditioning is the main contributor to reduced fuel economy in hot weather. Its effect depends on a number of factors, such as the outside temperature, humidity, and intensity of the sun. Under very hot conditions, AC use can reduce a conventional vehicle’s fuel economy by more than 25%.1,2 The AC’s effect on hybrids, plug-in hybrids, and electric vehicles (EVs) can be even larger on a percentage basis.2

Driving with your windows down can also reduce fuel economy. Open windows increase aerodynamic drag (wind resistance), making your vehicle use more energy to push through the air. This effect is quite small at low speeds but increases at highway speeds.

…more at http://www.fueleconomy.gov/feg/hotweather.shtml