How much fuel does a car consume in one hour at idle speed?

[MarcusLee]

When the engine is running at idle speed, the fuel consumption is related to the engine's own displacement. Taking a 1.6L displacement engine as an example, at an idle speed of 800 rpm and without additional loads such as air conditioning or radio, if it runs for one hour, the fuel consumption is approximately 1011.2 milliliters, which means slightly more than 1 liter. The following are relevant details: 1. Vf represents the fuel consumption per hour, measured in milliliters per hour; V refers to the engine displacement, measured in liters (L); n is the engine speed per minute (rpm). According to the above formula, when a car has a displacement of 2.0L and a speed of 700 rpm, the fuel consumption at idle speed for one hour is calculated as 0.792.0700=1106 milliliters. 2. If the air conditioning is turned on while idling, another formula is needed to calculate the fuel consumption: Vf=0.02636PV*n (ml/h), which also gives the result in milliliters of fuel consumed per hour. Compared to the previous formula, this one includes an additional parameter P, which represents the manifold pressure at idle speed. There are two ways to obtain this data: using professional instruments to measure it or utilizing the vehicle's onboard computer to read the data transmitted by sensors.

[VanLevi]

I've driven many cars before, and idling for an hour really wastes a lot of money on fuel. Small-displacement cars, like those below 1.5L, consume about 0.5 to 1 liter per hour; larger SUVs or pickup trucks can go up to 1.5 to 2 liters. Calculate the current fuel prices, and you can save anywhere from a dozen to several dozen dollars. I've tried idling with the AC on, and the fuel burns even faster, so now I turn off the engine if I'm parked and waiting for more than 5 minutes. In summer, when waiting in the car, I just roll down the windows for a breeze or find some shade and turn off the engine—saving fuel and avoiding engine carbon buildup. Long-term idling not only wastes money but also increases exhaust pollution, and you’ll end up spending more on repairs later. For ordinary families, the best way to save money is to develop a habit: buy a small timer for parking, or bring a book to pass the time and avoid unnecessary idling out of boredom.

[McOmar]

When a car idles, the engine runs without load, and fuel consumption varies significantly over an hour. Simply put, a small 1.0L displacement vehicle may consume around 0.5 liters, a typical 1.6L family sedan about 0.8 liters, while larger models with 2.0L or above can reach up to 1.5 liters. The reason lies in the idle speed maintaining low power output—fuel burns slowly but inefficiently. Running the air conditioning adds an extra 0.2 liters of fuel consumption, and warming up the car in cold weather has a similar effect. Carbon buildup is a hidden risk; incomplete combustion over time degrades engine performance, leading to costly repairs. It's advisable to regularly use an OBD tool to measure your car's idle fuel consumption and develop good habits to minimize unnecessary idling. Don’t assume idling is harmless—every liter of fuel burned is a source of pollution. Checking for carbon deposits during oil changes is a safer practice.

[LeStephanie]

Concerned about environmental protection, the fuel consumption from idling for an hour is heartbreaking. Small cars consume about 0.5 liters, while large vehicles nearly 2 liters, meaning significant CO2 emissions. The resources wasted per hour equate to driving an extra 10 kilometers and polluting the air. Don't underestimate this fuel—global idling adds up to massive energy waste. Promote energy-saving behaviors: turn off the engine during short stops, and use public transport instead of waiting in a running car. Everyone's effort to reduce idling can contribute to the planet.