I recently had an oil change at servitek, the oil they used was mobil special (cheapest oil they probably had), the oil is rated SG. I realized later on that the car manual specified to use at least oil rated SH, would there be any bad effects if I keep using the lower rated oil for the next 1000km?

The only reason I opted for a cheap oil change is due to an oil leak in my distributor, I'll have the leak fixed within the next couple of weeks and then probably have another oil change, most likely royal purple 20w-50.