using a too thin an oil will wear it out quicker I believe. It might increase performance very, very slightly as there is less resistance. You would NEVER notice it on a road car, and I might just be wrong! LOL

yip 0/40 is to thin.. i use 10/40 semi synthetic

u will not get increased performance by using mobil 1 oil, using 0/40w is too thin & your corsa will drink it like its going outta fashion

as a general rule of thumb the more miles your car has done then the higher the viscosity rating you will need.

putting the wrong oil in will not do any real damage. simple thing is to give it an oil change

Not sure m8, but may not b the oil that makes ur car run rough. Anyway 10/40w is the correct stuff, although it can run on other. I use Mobil 1 which is 0/somethin, can't remember. Engine sounds tappy but this will increase performance. (£31.99)

What would be the consiquences of putting the wrong oil in your car? Its just my car runs a little rough and think the previous owner may have been using the wrong oil....:) cheers!