The possibility of allowing a test mule to be used at 'engine-only' track test sessions has been discussed but has not found favor.

McLaren technical director Paddy Lowe said at Spa: "It is expensive to make a mule car, not only in terms of money but also in terms of the people you need to design and run it. Most of the teams have agreed that we will not have mule cars. The regulations currently wouldn't make them a benefit and we are not agreeing to introduce any new test sessions."

While it is understood that there is belief that the engines can be reliably introduced after extensive dyno testing that has already begun, Ferrari's Mattia Binotto autioned: "On circuit running, with things like gear changes over bumps is very different from running on a dyno. There will be worries about finding problems and being able to sort them out, but we will accept decisions and work within them."