Not so long ago, people tried to save gas by leaving their car running when they went to a convenience store instead of restarting it when they came out. The theory back then was that starting your car used more gas than letting it idle for short periods of time. Some people still do it today, but does it save gas in newer cars?
Does it take a lot of fuel to start a car?
Cars built before the 1980s provided the air-fuel mixture that the engine burns using a different system than vehicles made in the last 30 years. This early system used carburetors to spray fuel into the airflow feeding the engine, and although there was some room for adjustment, it had to provide enough gas for the engine in all conditions. This requirement meant that the air-fuel mixture was “rich” in fuel most of the time.
There is no continuous airflow feeding the engine when the carbureted engine is shut down. Thus, carburetors must dump excess fuel into the engine’s air intake when starting to ensure easy starting.
Newer cars use a computer-controlled fuel injection system that delivers precise amounts of fuel to each cylinder of the car’s engine only when needed. It Still Runs tells us that on average it only takes about 1/2 teaspoon of gasoline to start the engine. Although this will vary slightly depending on engine size, number of cylinders and tuning, this is a predictable average to keep in mind.
The South Carolina Department of Health and Environmental Control also released a fact sheet stating that an idling car engine “consumes up to 1/2 gallon of fuel per hour.” For reference, there are 768 1/2 teaspoons in a 1/2 gallon.
Will a gallon of gasoline start a car?
Now that we know that most car engines start with 1/2 teaspoon of gasoline, that seems like a simple answer. So how much gas does your gas tank need to start your car? If your car’s gas tank is empty, adding 1 gallon of gasoline should be enough for the fuel pump to pick it up and deliver a stream of fuel from the tank to the engine.
Does a car start if it’s out of gas?
If a car runs out of gas, the car’s engine stops. If you try to restart it without adding gas, it may try to start, sputter, run for a second or two, then die again. A gasoline car will not run without a sufficient amount of gasoline.
If you keep trying to start it without enough gas in the tank, it could damage your car’s fuel system components or your car’s engine. For example, your vehicle uses a fuel pump to send gasoline to the engine injectors from the gas tank. This fuel pump depends on the gasoline it pumps for lubrication and cooling and could overheat without it. In addition, your engine will suffer because burning an air-fuel mixture lower in fuel than intended causes explosions in the cylinders which can break off spark plug tips and burn out engine valves.
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