Charcoal gets treated as an afterthought — the thing you buy at the same time as the meat, chosen on price and bag size. On a twenty-minute grill that is a perfectly reasonable attitude.
On a brisket it is not, because a brisket cook is long enough that the small differences compound. A fuel that leaves twice the ash produces a genuinely different fire by hour ten. A fuel that burns dirty puts unwanted compounds through your meat for the entire smoke absorption window.
What lump charcoal actually is
Hardwood, burned in a low-oxygen environment until the water and volatile compounds have been driven off and what remains is essentially carbon. Nothing is added. The pieces keep the shape of the wood they came from, which is why the bag contains irregular chunks rather than uniform pillows.
Briquettes take a different route: sawdust and char fines, compressed with a binder into identical shapes. The uniformity is the product. So, unavoidably, is the additional non-combustible material that ends up as ash.
We go through the full comparison in lump charcoal vs briquettes, and the conclusion there is not that one is superior — it is that they suit different cookers.
Why lump suits a brisket cook
It lights faster and gets to temperature sooner. Minor, but it removes an hour of standing around at the start of an already very long day.
It burns cleaner. Fewer additives means fewer combustion products that are not simply heat. Given that a brisket sits in that atmosphere for its entire smoke-absorbing phase, a clean base fire is worth having — and it is one of the contributing factors in bitter or acrid brisket.
It leaves less ash. The most practical advantage and the one people underestimate. In a bullet smoker, the fire sits above a bowl and draws air upward through the fuel; as ash builds, it insulates the unburnt charcoal below and restricts that airflow. Temperature drifts down late in the cook for no apparent reason, and the reason is ash.
It runs hot. Useful when you want to push the back half of a cook, and something to manage with your vents when you do not.
Why oak specifically
Because the small amount of character the base fuel does contribute may as well point in the same direction as your smoke wood. Oak lump under post oak chunks is a coherent fire — everything in it is oak, which is what a Central Texas pit is burning.
It is a small effect. But it costs nothing to line it up, and it removes one variable from a cook that has plenty.
Where briquettes still win
We would not use lump for a snake-method kettle cook. The snake method depends on laying a precise, even train of fuel that lights progressively at a predictable rate, and uniform briquettes do that in a way that irregular lump simply cannot. The predictability is the technique.
Briquettes are also usually cheaper per hour of burn, and if you are cooking on a tight budget that is a legitimate reason to choose them. Nothing about a brisket requires lump.
Who should buy it
Anyone running a bullet smoker, a drum, a kamado or a gravity feeder, where fuel sits in a basket or hopper and burns from one face. In those cookers the low ash and clean burn are genuine operational advantages across a long cook, and the irregular piece size costs you nothing.
Kettle cooks running a snake should buy briquettes and spend the difference on better smoke wood, which is where the flavor actually comes from.