If performing a system change out is not an option, AIS can provide you with a compatible top-off fluid at a very competitive price. See the table below for options:
Shell Turbo DR 46 -> Fyrquel EHC N
Shell Turbo S5 DR 46 -> Fyrquel EHC
Shell Turbo S5 DR 46 -> Fyrquel EHC Plus
Shell Turbo S5 DR 46 -> Fyrquel EHC S