Choose what ever suits your budget, but change oil and filter yearly - I've read mid year filter only changes can be beneficial on their own I'm Sure there are GTX (cheap mineral) users on here, Magnatec (midrange semi), I use millers NT (very not cheap full synth) - amongst a wh...
I have a 2003 BMW R1150GS and I need to top up the oil but im yet to find a definite answer as to what oil I need, looks to be either 15w50 or 20w50. the best I can find locally is a semi synth 20w50 from Halfords. this seems to be what James Sherlock stock for the 1150...