This really isn't needed on modern fuel injected vehicles, especially on petrol (gas) vehicles. The only thing you are really heating up is the cabin. Idling fo

This really isn't needed on modern fuel injected vehicles, especially on petrol (gas) vehicles. The only thing you are really heating up is the cabin. Idling for 1-2 minutes when it's below freezing may be beneficial, but leaving a modern car idling for 15 minutes is a waste and doing nothing other than making it more comfortable for you. Once it's idling at a stable RPM, just start driving and take it easy for a few minutes. The main part of the engine that needs to be heated up when cold is the oil, so that the viscosity is low enough to allow it to flow to all the parts of the engine it needs to reach. Modern oils do not have any issues being viscous even when cold, just make sure you use the right oil for your vehicle & climate, and change it on schedule. Diesel engines are usually physically bigger and the combustion temperature is lower than petrol, so it takes longer to heat up. The biggest issue with a diesel is actually starting it though, that's why in colder climates diesel vehicles usually have a Webasto or similar device to preheat the coolant for you which will make it easier to crank. Of course there are exceptions to this advice if you live in extreme climates, but NYC is usually not that extreme.