I put a can in the engine and one in the gas tank about 2 days ago, will it hurt anything if i leave it in for a little?

 

You put a FULL can of seafoam in the oil!? Hell yeah it could hurt something, its a solvent! You only need half a can in the oil max. If you let it sit in there too long (especially a full can) can spin a main or rod bearing. Meaning you will need to re-build your engine. I would drain the oil ASAP, its more than likely clean if you ran the engine.
It won't hurt anything being in the fuel.

 

OK I'm going to change the oil today, will it be ok to make a 15 mile trip? I put it in Friday afternoon, driven it maybe 10 miles since then. I guess i should read the can, didnt know it was a complete solvent

 

Emergency oil change done. Oil did not look or feel that bad, didnt smell like anything but oil. But someone answer me why an engine with such small tollerances and only 3 liters needs a 5-40 oil??

 

Plain bearings are designed with the viscosity of the oil taken in to account since the outer bearing surface (ex. - rod) actually floats on a thin layer of oil not the inner (ex. - crank) bearing surface.
My manual says 5W - 30 or 0W - 30. I guess in hotter temps a 5W - 40 MAY be called for... Most likely it provides no better lubrication and robs horsepower.

 

5W-40? Wierd. I use 0W-30 per the manual and the sticker on the car.

 

Maybe we can get a tech to ring in, what oil is good to use for a 3 liter?

 

the cap says 5W40, I use 0W40.

 

Depends on the outside temperature really. If you plan on driving around in 100+ degree temperatures then stick with the 5W40 as its heavier and we all know heat thins out oil.
If you plan on running in cooler temps anything from 0W-30, 5W30, 0W40 is all good. Never put in anything heavier than that under any circumstances, example: 10W40 is way to heavy. I have always ran synthetic 5W-30 in all my audi engines because it gives good overall temperature protection and sufficient engine protection, thats just me though.

 

For what it's worth, Mobil1 0W-40 states "European Car Formula" on the bottle while 0W-30 and 5W-xx do not. I use at least a 0W base because of the turbos. I'm not convinced that -30 is better than -40 weight or vice versa since I don't live in an area of extreme heat.