It had been claimed the Brackley team may run its prototype design, aimed at increasing the volume of this year's turbo V6 engines, in free practice.
But a Mercedes spokesman told the Austrian news agency APA that the exhaust attachment will actually only make its debut at the post-race test.
"We'll see there if it has the lasting effect that we want," team boss Toto Wolff is quoted as saying.
APA said the results of Mercedes' exhaust test will be sent directly to the FIA, who will decide on the next steps.
"The aim is to find a workable solution for everybody by the Canadian grand prix on June 8," the report revealed.