Measure 230V mains with 300V CAT II probe?
300 Cat II is okay for connection to low power fused mains circuits up to 300VDC or 300V RMS (fault current under 100A, I think). 

If you've got an industrial mains circuit or one otherwise capable of high fault currents, Cat III or higher would be necessary. 

That also assumes your scope can directly handle an input of +/-31V (eg. 10V/div). 

Note also the limitation on voltage on the reference relative to earth! 



I use a Tek TPS2024 for mains measurement- the isolated channels are a big advantage (though you have to sign a contract every time you power it up not to exceed the 30V limit).