As a renter am I responsible for damage caused by owner's negligence?

Yes, you are responsible, because an act you did--spilling oil--caused damage to the owner's property. The owner was not negligent--whether or not it is better to seal granite or they sealed other granite, there is no duty to do so, nor is it unreasonable to not have sealed it; many people do not seal granite. Your act caused damage to the counter as it exists, so you must repair or replace it. Consider it this way: laminate counters are more easily damaged than granite by moisture or by scratches. By your logic, if you damaged a laminate countertop by cutting meat directly on it, so scratching it up and getting moisture into it, it would the owner's fault for not having installed a solid surface, which is more resilant in the first place. However, this is not how the law works.

The owner is not at fault for not having taken every precaution available, when what he had, unsealed granite, is perfectly common and reasonable. You are liable for damaging the owner's property, and he may use your deposit as an offset against costs.