What car you looking at fitting it to ? Lcr engine code ?
There's a thread on fitting an oil temp gauge if you use the search but pretty much route the wiring from the engine bay up behind the air box and though a rubber grommit behind the pollen filter then to where ever you want it in the cabin ( I took the wiring feed off my headlight switch )

As far as the sender on the lcr at least above the oil filter is a plate it screws onto, on that plate is the space to add a temp gauge sender. Just undo the bolt acting as blanking plate thread the sender I wanna saw its a m10 and attach to everything else.

Hardest bit is routing the wiring behind the dash, the rest is straight forward. Just time consuming I did in 2/3 hours.....
 
Its a bam engine cupra r ..... I put a boost gauge in my so I no that bit... What type of hose do u run in between the two
 
I'd go for a stainless braided line. there's one on demon tweeks but I can't post links yet :whistle:

Probably about 10ft to make sure you have enough to route it neatly .... Just match the ends with your sender and the back of the gauge
 
I've fitted savage gauges, cheap as chips of the bay but look as close to standard clocks as I could find (white background, red light) they do what they're supposed to do and the boost one at least is v accurate for the money