Solved

Strategy Bug(-ish)

This bug is killing me on Races, and I just notice how it works. So the bug is that when I was on the Chinese GP, penultimate lap, and I had 1.6 laps on fuel left, but the game pitted me for no reason, automatically. I don't even have a warning. I did it once on the first season when I'm new to the game.

SETUP:

2-Pit Stop Strategy:
Soft Tires

8/10/11 laps of fuel 
29/28 laps

I started with 8.4 laps of fuel, 1st PIT (Lap 7/28): 0.7+10 laps of fuel, 2nd PIT (Lap 17/28): 1.0+10 laps of fuel...
Then the unnecessary (The Bug) 3rd pit stop happened.  

HI Azzy,
I think this is the point where you may have miscalculated - 2nd PIT (Lap 17/28): 1.0+10 laps of fuel...

What I understand how the game works is that if you have 1 lap of fuel left and pit for 10 laps it will only add enough to take you to a total of 10 laps and not add 10 laps worth of fuel to your already remaining 1 lap which in theory would equal 11 laps and enough to get you home.

Hopefully one of the more experienced managers can confirm or deny this theory.

So instead of adding 10 laps of fuel to the remaining 1 lap left it adds 9 laps of fuel. Thanks for clearing this out for me. 

This bug happened to me in my last race.  My second driver had about 15L of fuel left before pitting to get off rain tires, put 34L of fuel in during stop, and came out with 34L of fuel instead of 49L of fuel.  He had to make an extra pit stop because of this.  You might be on to something Andy Craig.

As mentioned above, fuel is topped off at the selected value (34 litres), not added to.