I'm interested in how race strategy changed during the refueling eras. Say we have a 60 lap race, you could pit on lap 20 and 40, or you could pit on lap 21 and 42. I wanted to see which strategy would be best on paper, using a very simple approach. Firstly, I assumed that pit stops don't cost time (both strategies require 2 stops anyway).
Secondly, I assumed that each extra lap of fuel difference between the strategies costs 0.1 seconds. So for example, on lap 1 the first strategy is 0.1 seconds. Having used these assumptions, I found that the strategy which pits on laps 20 and 40 is 0.3 seconds faster.
I'm struggling to understand why this is? If both strategies fuel up 60 laps of fuel over the stints then surely the pace should be the same? Taking this to its extreme, if you pit on lap 58 and 59 you are -6952.4 seconds slower. Using my knowledge of F1, this makes sense, but when thinking about it mathematically it doesn't make as much sense. Why does it matter how you split up the 60 fuel load, as long as it's split into 3 portions?