Suggested

Pit stop delta?

Many high level managers have already got this information. Private lobby Quick Races are probably the best way to obtain accurate pit loss because you can ensure Boost and DRS on the in and out laps are not active. Alternatively a couple of accounts in a private league but gathering the information this way takes much longer because you can only race once a day.

Remember, in a no refuelling race the stationary time is only 3 seconds to change the tyres whereas if you're running long stints in a refuelling race the pit loss might be slightly longer because of loading large volumes of fuel.