If you're asking for oil change instructions, you'll no doubt eventually run into someone that advises running the car to heat up the oil before you start.

Having always waited for my engine to cool, this sounded crazy so I wanted to do the research so you guys all know what's the best way to go.

Reasons cited for changing it warm:

1. Hot oil is thinner, and drains faster
2. Warm/mixed oil could suspend more particulate and contaminants.
3. Hotter oil will drain more completely from various parts of the engine
4. A recently run engine will be better lubricated upon restart
5. Warm oil filter seals may be easier to remove
6. My dad taught me this way.

Reasons cited for changing it cold:

1. No worries about getting burned.
2. It doesn't take that much longer, if at all.
3. More oil will have drained into the oil pan since it's been sitting longer.
4. More drained oil means more suspended contaminants will come out with the oil.
5. A cold engine start after an oil change isn't that bad, especially if you pre-fill the filter.

So, should you change oil hot or cold?

In the end, the most important thing is you change your oil. Any advantage either method gives you is arguably minuscule and has no real bearing on the life of your engine. Find what works best for you and stick with it.

Personally, i prefer cold, it gives me much more time to look around the engine components and look for other problems without worry of burning my hands or arms. Others will prefer hot for speed or convenience.