Graded modal types systems and coeffects are becoming a standard formalism to deal with context-dependent, usage-sensitive computations, especially when combined with computational effects. From a semantical perspective, effectful and coeffectful languages have been studied mostly from a denotational perspective and almost nothing has been done from the point of view of relational reasoning. This gap in the literature is quite surprising, since many cornerstone results on concrete coeffects - such as \emph{non-interference}, \emph{metric preservation}, and \emph{proof irrelevance} - are inherently relational. In this paper, we fill-in this gap by developing a general theory and calculus of program relations for higher-order languages with combined effects and coeffects. The relational calculus built upon the novel notion of a \emph{corelator} (or \emph{comonadic lax extension}) to handle coeffects relationally. Inside such a calculus, we define three notions of effectful and coeffectful program refinement: contextual approximation, logical relations, and applicative similarity. These are the first operationally-based notions of program refinement (and, consequently, equivalence) for languages with combined effects and coeffects appearing in the literature. We show that the axiomatics of a corelator (together with the one of a relator) is precisely what is needed to prove all the aforementioned program refinements to be precongruences, this way obtaining compositional relational reasoning about combined effects and coeffects.