Not likely to be the oil, They may have put a thicker oil in but you will just get slower cranking speeds and maybe a bit more noise until the engine warms the oil.
Get a code reader & see if there are any codes stored.
More likely injectors or inlet manifold/egr gunged up.
Get a code reader & see if there are any codes stored.
More likely injectors or inlet manifold/egr gunged up.