Hey there

If you want to prepare for UPSC civil services then technical portion is not going to help you in the exam unless and until you take your branch paper as your optional but a few do this because branch paper is tougher than usual subjects people choose. I can understand that you want to be on a safer side that is why you want to do engineering and want to prepare for UPSE alongwith. But doing this you will not concentrate on either of them and you will hamper your studies. I would suggest you that if you want to do UPSE then join some reputed colleges and do graduation do not waste money on something you don't wanna become. You will have more chances of clearing UPSE with graduation like this rather than engineering.

Good luck