It wasn’t that long ago that people used to try and save gas by leaving their cars running when going into a convenience store instead of restarting them when they came out. The theory back then was that starting your car used more gas than leaving it idling for short periods. Some people still do this 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 the engine burns using a different system than used by vehicles made in the last 30 years. This early system used carburetors to spray fuel into the airstream feeding the engine, and while there was some room for adjustment, it had to supply enough gas for the engine under any condition. This requirement meant that the air-fuel mixture was “rich” with fuel most of the time.
There isn’t a continuous airstream feeding the engine with the carburated engine shut off. So, carbureters have to dump excess fuel into the engine’s air intake during start-up to ensure easy starting.
Newer cars employ a computer-controlled fuel injection system that delivers precise amounts of fuel to each car engine cylinder only when needed. It Still Runs tells us that, on average, it only “takes about 1/2 teaspoon of gas to start the engine.” While this varies slightly depending on the engine’s size, the number of cylinders, and tuning, it’s a predictable average to keep in mind.
Now that we know that most car engines will start on 1/2 teaspoon of gas, that seems like a simple answer. So, how much gas needs to be in your gas tank to start your car? If your car’s gas tank is empty, adding 1 gallon of gas should be enough for the fuel pump to pick it up and deliver a fuel stream from the tank to the engine.
Will a car start if it’s out of gas?
If a car runs out of gas, the car’s engine will shut off. If you try to start it again without adding gas, it may try to start, sputter, run for a second or two, and then die again. A gasoline-powered car will not run without a sufficient amount of gas.
If you keep trying to get it to start without enough gas in the gas tank, it could damage your car’s fuel system components or engine. For example, your vehicle employs a fuel pump to send gas to the engine’s injectors from the gas tank. This fuel pump relies on the gasoline it pumps to provide lubrication and cooling and could overheat without it. Additionally, your engine will suffer as burning an air-fuel mixture that is lower on fuel than designed causes explosions within the cylinders that can break spark plug tips and burn engine valves.
How much gas does it take to start a car after it runs out? To restart your car, it only takes a gallon or so of fuel. But however much you fill up the tank, be sure it's enough to get you to the nearest gas station.
If your engine is cold it'll use a lot of fuel over the first couple of minutes as even hybrid cars will run the engine to warm up the oil. But if your engine is already hot then restarting it takes very little fuel. That's why modern cars have stop-start engines.
Starting a cold gasoline engine does use an extra charge of fuel, in part to compensate for the higher density air. This 'extra' amount is approximately what is burned during 1–2 minutes of idling.
Typically, engines need five to eight quarts of oil. However, the size of your engine can impact how much oil is required. For example, a 4-cylinder oil engine may require around five quarts of oil, whereas a 6-cylinder oil needs six quarts. Usually, the smaller the engine is, the less oil you'll need for your vehicle.
NAPA says you should be able to count on somewhere between 30 and 50 miles, with most cars having between two to three gallons of fuel left once the warning lights.
Anything between 2 lines would be an eight. If the needle were between 1/2 and 3/4, this would mean you have 5/8 of gasoline in your tank. The line lowest to the bottom would mean you have 1/4 of a tank of gas and you should probably fill up soon, below 1/4 would be close to 1/8 of a tank which means get gas now.
Broadly speaking, most modern cars can drive 20 to 35 miles on a single gallon of gas. Indeed, this is about how many miles you have left when the gas light comes on in your car.
The estimated fuel consumption of an idling engine is 0.6 litres / hr per litre of engine displacement. This means that an idling 3.5 litre engine consumes more than 2 litres of gas per hour. Letting your engine idle 30 minutes a day for two winter months burns a full tank of gas without ever moving a kilometre!
On modern cars turning on (starting) an engine does not consume any more fuel than an engine that is already running. The only time an engine may consume extra fuel is on a cold start first thing in the morning. An engine that is not running is not consuming any fuel. Start and stop will save fuel.
Of course the difference between ambient temperature and normal engine operating temperature is greater in cold weather than warm weather. This means that the engine takes longer to warm up and therefore spends more time consuming an air/fuel mixture that is much richer in fuel.
The vehicle warms up faster when driving than it does when idling. NOx and THC emissions from restarting are larger, but at least an order of magnitude lower than those from starting a cold engine (Table 2). For short stops, it makes sense to turn the vehicle off in order to minimize fuel use and CO2 emissions.
While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 50 mph. You can assume that each 5 mph you drive over 50 mph is like paying an additional $0.25 per gallon for gas. Observing the speed limit is also safer.
Nipping out on lots of short journeys, particularly in urban areas, also drains the battery, as it takes 150-350A of battery power just to start the car, and on short trips the alternator won't have the time or capability to replace this charge.
Idling for just 30 seconds wastes more fuel than restarting the engine. Idling is harder on the engine than restarting. Frequent restarting causes only about $10 worth of wear-and-tear per year, whereas idling leaves fuel residues that damage engine components and cause higher maintenance costs over time.
Idling for more than 10 seconds uses more fuel (Figure 3) and emits more CO2 than engine restarting. Idling fuel usage varies from 0.2 to 0.5 gal/h for passenger vehicles across a range of sizes, and increased with idling speed. The vehicle warms up faster when driving than it does when idling.
According to Idle Free California, an organization dedicated to reducing the amount of time that vehicles are left running while they are parked or stopped, idling wastes an average of 0.9 gallons per hour in most vehicles.
You need to let the fuel system prime everytime before you start the car. That way you will have enough fuel pressure to start right up. You can even hear the pump workin. Even if you prime your fuel system, when your tank is low it will be harder to start.
Introduction: My name is Horacio Brakus JD, I am a lively, splendid, jolly, vivacious, vast, cheerful, agreeable person who loves writing and wants to share my knowledge and understanding with you.
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