The most significant sporting regulation change will be the banning of mid race refuelling. With the removal of refuelling the fundamental character of races will change immensely. Refuelling has been a part of Formula 1 since 1994 and its return heralded a period where races became flat out sprints between pit stops. As a result it is easy to see why the FIA decided that the practice of refuelling has been one of the major obstacles in allowing for overtaking on the track.
By removing this element we will now see significant changes in the tactical aspects of Formula 1. The drivers obviously have to start the race with enough fuel to make it to the finish of the race; therefore cars will be very heavy on the start line for races. The cars will get significantly faster as the race progresses fuel is burnt off, in the past the main factor controlling the speed of an F1 car has been the condition of the tyres because a car would invariably have only 50-80g of fuel to allow for up to half a race distance. Now though with drivers forced to have a fuel load of up to 180kg of fuel from the start the main factor controlling speed is the sheer weight of fuel in the car. The more fuel is burned the faster the car will get even when tyre wear is taken into account.
In the past, a driver made a pitstop and took on fuel and change tyres. Back on the track, he would lose time because the fresh tyres would not be able to overcome the weight penalty of the heavy fuel load. In those circumstances it was advantageous to pit later than your rival, however out refuelling the driver who pits earlier will have the advantage due to having the fresher tyres and being able to exploit them while their rival is still on track with old rubber and a similar fuel load. This will see drivers pitting earlier than expected so as to be ahead of a rival after the pitstops are made.
To see how this new regulation might lead to more exciting races consider the following scenario where two drivers are fighting for the win and the lead driver decides that they will pit early so as to maintain the lead after the pits. Normally the driver would make their stop at one and two thirds distance, i.e. laps 20 and 40 of a 60 lap race. However to ensure he maintains the lead the driver pits on lap 16. This change in strategy will allow him to stay ahead but will have repercussions later on in the race. The next stop was scheduled for lap 40; can the tyres now go that long? The driver must now decide whether to drive conservatively until their next stop or continue pressing hard and pit out of sequence again? The team make the decision to stop the driver a few laps early again and pit him on lap 34. He now has 26 laps left to nurse his car to the end of the race having done no stint longer than 18 laps while his rival will have pitted on schedule and will have tyres much more suitable for the final stint. Can the lead driver hold off the hard charger with fresh rubber? This will be a familiar sight as races come to a close this season!