IndyCar will reintroduce grid penalties for unapproved engine changes this season for the first time since 2013.
Any car that has its engine changed before a manufacturer's pre-determined mileage limit has been reached will suffer a grid penalty in the next race - a six-place drop for road/street courses and a nine-place drop on ovals.
A full-season entry is allocated four engines for a season that covers approximately 10,000 miles including race weekends, team tests and open tests, so both Chevrolet and Honda will be required to declare an approximate mileage limit of 2500 per engine.
Given that the current 2.2-litre turbocharged V6 engine formula has been in place since 2012, the engines can be expected to be reliable, but are by no means bullet-proof, with Team Penske driver Josef Newgarden requiring six Chevrolet units on his way to last year's title.
As well as an engine reaching its pre-determined mileage limit, engine changes that will not incur a penalty include switching to a test unit for an engine manufacturer test or for special events such as the Indianapolis 500 pitstop competition or demonstrations at non-race events, such as the drive across San Francisco's Golden Gate Bridge in 2015 to honour the recently deceased Justin Wilson.
For entrants with multi-engine Indy 500 programmes, a fresh engine can be used before the race. Both engines will remain with that entrant, and both must be used before any other engines are allocated.
The entrant can choose which engine is utilised for the next event, but that engine must remain in the car until it reaches the change-out mileage.
Penalties will not be incurred for engines that suffered crash damage, so long as evidence of the damage is presented to IndyCar, only the parts that were damaged in the crash are replaced, IndyCar approves the change and the repaired engine is returned to that entrant.
Any engine change that doesn't fall under the conditions mentioned above will be regarded as non-approved and incur a grid penalty.
If the change is initiated by the entrant outside the prescribed conditions, rather than the manufacturer, the driver and entrant will lose 10 points as well as suffering the grid demotion.
If the unapproved change occurs at or follows a test, the penalty will be served at the next race event.