I'm assuming this all relates to a standard engine? Because after I got my forged rebuild back from API the paperwork they gave told me i MUST warm the car up for 5-10 minutes before driving due to risk of piston slap. I know in reality this is very difficult to sit and wait for 10 minutes but I would like to this David and the boys down at API know a few things about subaru engines.

Tom

 

Piston slap can occure on standard engines too and usually goes once everything is up to temp.
I doubt API mean you have to let it idle for 10mins before moving. You must of misunderstood what he said chap.

 

Get in and drive it like you stole it.

 

You actually want the engine to get to working temperature as fast as is reasonably possible. Most wear occurs during a cold start cycle where there is metal to metal contact, such as piston rings, hence the piston slap on some engines.

Being on a cold start cycle the engine will run rich; you can probably smell fuel in the exhaust fumes. Whilst this isn't a massive problem, it will cause a little fuel dilution of the engine oil.

Myself: I just get in a drive normally, none of this below 2k revs for 10 minutes. As long as you're not thrashing the car it should be fine.

 

I get in, start up, belt up, sort my phones out/wallet/sunglasses (the one day a year we get sun!) etc then set off to work and as many others have said, I don't up the tempo until a good 10-15mins into the journey.
Then on the return home I stay off boost as much as possible for 1-2 miles before reaching home.