[align=center]Eight Auto Questions
By TOM TORBJORNSEN[/align][align=center]


Why do brakes squeal or squeak?[/align][align=center][/align][align=center][:-]
Brake squeal is the result of a high-pitched vibration of the brake pads. This vibration occurs because the pads are not properly insulated from the caliper or secured to the caliper. Brake pads come from the factory with anti-rattle clips, pad insulator shims, and sometimes a silicone backing that literally glues the pad to the caliper to keep the pads secure and to prevent rattle or vibration.

Sometimes brake squeal is the result of the composition of the brake pads being too hard. These hard, smooth surfaces rub against each other, resulting in the "nails across a blackboard" syndrome. If this is the case, replace the pads and resurface the rotors. That should stop the squeel. Finally, if the brake rotors are not re-surfaced when a brake job is done, it results in squeal. When brake pads are replaced, the rotors must be resurfaced with a non-directional finish applied to the rotor face to ensure proper pad break-in. In order for the pads to break in properly, pad material must be worn off (this happens when the rotor has been resurfaced properly and the brakes applied for the first 500 miles or so).

When brake squeal is evident, the tech should start with ensuring that the pads are properly secured and insulated to the brake caliper, and the anti rattle clips are installed to stop pad rattle. In addition, the tech should make sure the rotors were properly resurfaced for pad break-in. Finally, the pads themselves could be the culprits if all the aforementioned are in place.

What is the difference between "outside" and "recirculation" settings on your car's AC?[/align][align=center]
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"Outside" setting means just that, fresh outside air is being fed into the vehicle's cabin along with the climate-controlled air that the HVAC system is feeding into the cabin. "Recirculation" means that the air being fed into the vehicle's cabin via the HVAC is being recirculated without adding fresh outside ambient temperature air.

What is the difference between premium and regular gas?[/align][align=center][/align][align=center][:-]
The difference between premium and regular gas is the octane rating. Octane is the measurement of a gasoline's volatility factor in the combustion chamber environment. The lower the octane, the more volatile; the higher the octane, the less volatile (more stable).

Low octane fuel is more apt to pre-ignite or ping inside the engine. Some refer to this phenomenon as "engine knock." Engine Knock occurs when the fuel ignites in the upper regions of the engine before the spark is introduced at the high point of compression. To understand what's happening, you must first have a basic understanding of how an internal four-stroke internal combustion engine works.
[b]On the first stroke of the four-stroke cycle, the intake valve opens, the piston travels down, and the injection system injects a perfect air/fuel mixture into the combustion chamber. The suction or vacuum produced by the downward stroke of the piston is what draws the air/fuel mixture into the engine; this is called the intake stroke.

Now that the combustion chamber is loaded with air and fuel, the valves both close and the piston travels back up, compressing the mixture tightly; this is called the compre