All species of oak are generally believed to burn longer than other tree species. Oak does not put out the most heat, but it does stay burning longer than other kinds of firewood or cooking wood. While oak is not the best wood to get a campfire started, it is the best wood to keep a fire going.
There are over 400 species of oak trees and shrubs which can be found in Europe, Asia, the Middle East and the Americas. Many species of oak that grew well in one country were often imported to other countries in order to get the foliage, their acorns or the wood.
Even if you have cut up oak logs, if they are green, they will not burn because they are still too full of sap and moisture. Oak that is ready for the fire should be dry to the touch and often weights lighter in comparison to green oak logs. If you can bend a twig, it's still green. It needs to snap in two easily. Sawing and chopping green oak wood can also warp your tools because of the sap. Green logs sometimes need to be aged a year after they are cut in order to make a good fire.
Live oak trees are much easier to identify than a pile of chopped up wood. They are usually among the largest trees in the neighborhood with acorns and large leaves with lots of lobes. Oak fire wood has a distinctive scent, much like cork. Once you start cutting and sawing larger logs for the fire, you will recognize your local oak just from the wood grain.
Since oak wood is a hard wood, it takes a longer time to catch fire than soft woods like pine does. But once it catches, it burns at a steadier rate than many other woods, which can burn up seemingly all at once. Reserve your oak firewood for times when you need it and you can save on burning any wood unnecessarily. For example, if you need to boil a kettle, use pine and ash. If you need to simmer stew, then use oak.
You can age green oak wood and other hard woods better than any soft woods, because of their high temperatures needed to set them on fire. Place the green wood around a fire and it'll dry out. This works with already cut up chunks of wood or with sticks and small branches. Large logs that are too heavy to cut up need to stay in a sunny spot. If you start to saw one and you can't saw a straight line down the log, then it's still too green to use.
- Cork oak cross section. Image from Wikimedia Commons