I've been thinking of that 2.5 second difference in one lap, and how they could have achieved it. I just cannot imagine this was their true pace, even if Vettel turned everything up, and others were saving tires etc... 2.5 wasn't there in qualifying, or in practice.
So as a lamen I started thinking what they could have changed on the car before the start, and my only logical thought was the tires. Especially the rims. The regulations say they need to be made from AZ70 or AZ80 magnesium alloys. But who's checking that? Is that part of the post-race inspection?
So my theory is, what if they were only running the light alloy wheels on their first and second race stints, and then switch to a heavier wheel rim for their last stint so they match the car's minimum weight limit?
I don't know much about tire physics, but what if these wheels are 4-5kg heavier each? Would that kill cornering performance on a light car at the end of the race?