Friday degradation numbers are mostly a story about fuel

Long-run pace charts published after practice look authoritative and are built on the one variable nobody outside the garage can see.

Every Friday evening somebody posts a chart of long-run lap times with a neat trend line through each car, and every Saturday somebody quotes it as if it settled the race. The chart is not useless. It is just measuring at least two things at once and reporting them as one.

Start with the mechanism. A car burns fuel through a stint, gets lighter, and goes faster. The rate is broadly known and it is not small over a long run. Meanwhile the tyre gives up grip, and the car goes slower. What you see in the lap times is the sum of a rising line and a falling line. Unless you know the starting fuel load, you cannot separate them, and starting fuel load is precisely what teams do not publish.

A team that wants to look fast on Friday runs light. A team that wants real data runs heavy and looks mediocre. Both produce a chart. The public reads them as if they were comparable.

Then there is the compound question. Two cars on nominally the same tyre may have taken it from different points in their allocation, may have scrubbed it differently, may be running very different downforce because one of them is still evaluating a floor. Aggregate all of that into a single degradation figure per car and you have produced a number with a decimal point and no meaning.

My argument is that the useful signal on a Friday is not the slope at all. It is the shape. A car whose times fall away sharply in the first three laps and then stabilise is telling you about thermal degradation, which is often a setup or driving problem and can be managed. A car that is steady for eight laps and then falls off a cliff is telling you about wear, which cannot. Those two profiles demand opposite race strategies, and both can produce the same average slope.

I would rather see three consecutive laps and know their fuel corrected values than see twenty laps and guess. Consistency of the lap trace across a run tells you whether the driver is managing or driving.

The teams know all this. They have their own fuel numbers, their own tyre temperature data, and a model. What they do not have is certainty about anyone else, which is why paddock estimates of a rival's race pace are frequently wrong by a margin that would decide the grand prix.

Everyone is reading tea leaves. Some people have better tea.