Keeping your bobbin case clean is absolutely a must. I clean mine out after every bobbin change. I also use a drop of oil on the race every so often...then run my machine so it throughly oils that area...then I use a scrap piece of fabric with batting to make sure there is no oil leakage to ruin my fabric. I do this on my computerized Pfaff 7570 which many don't believe should be oiled but it does keep the race running smoothly. Some days my Pfaff is running 8/9 hours and imho adding a bit of oil to a constantly moving part just keeps it purring. My mechanicals seem to need more oiling to keep them purring. I cannot emphasize enough to keep your bobbin area clean...your machine will love you for it.
You should also see open holes (not the ones where you can see screws) that you can put a drop of oil. Does your manual not have a trouble shooting area or maintenance type section for you to learn how to do this....sometimes it may be in an odd place in your manual that could be easily overlooked.