range rover1996 dse Hot starting

Hi to all out there I have the hot start relay fitted on my motor Can i fit the 15 second timed relay on same pin numbers The relay is off a 1986 classic.I think the hot start relay on my range rover has done my fuel 17.5 mpg I had the normal relay fitted for a week was gettin 23.9mph
cheers Pete

dint yu ask this earlier?

Yes i did sorry im new here its my first time cheers pete