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• $48 for three oil changes (a $86.85 value)
• $16 for one oil change (a $28.95 value)

Internal-Combustion Engines: The Muscle in a Muscle Car

An oil change keeps all the parts of an engine moving smoothly. Peek under the hood with us to see why they need constant lubrication. Beneath the guttural rumble of a car engine is an incredible amount of force. As soon as you step on the gas, fuel vapor mixed with air begins exploding, driving metal pistons in and out of chambers where temperatures regularly hit 3,000 degrees Fahrenheit. This enclosed system of pistons propelled by direct contact with burning gas defines an internal-combustion engine. (There is such a thing as an external-combustion engine, in which the heat is produced from outside the cylinder—as in the old-fashioned steam engines that people in the past used to make trains look extra friendly, for instance.)

The internal-combustion engine under the hood of the typical car completes its cycle in four stages, or strokes. First, fuel and air fill the cylinder as the piston drops. As the piston returns to the top of the cylinder, it (2) compresses the fuel mixture before (3) a spark from the spark plug ignites the mixture, the force of the explosion pressing the piston back down. Finally, the cylinder rises once more to push out the exhaust. As the crankshaft at the base of the pistons is kept turning by this constant cycle, it drives the rotation of the transmission, which applies all that power in a controlled fashion to the axles and, finally, sends you speeding down the road.