diff --git a/opm/core/transport/implicit/ImplicitAssembly.hpp b/opm/core/transport/implicit/ImplicitAssembly.hpp
index b6facff..672623c 100644
--- a/opm/core/transport/implicit/ImplicitAssembly.hpp
+++ b/opm/core/transport/implicit/ImplicitAssembly.hpp
@@ -107,13 +107,13 @@ namespace Opm {
         template <class Grid>
         int
         countConnections(const Grid& g, int c) const {
-            int i, f, c1, c2, n;
+            int n = 0;
 
-            for (i = g.cell_facepos[c + 0], n = 0;
+            for (auto i = g.cell_facepos[c + 0];
                  i < g.cell_facepos[c + 1]; ++i) {
-                f  = g.cell_faces[i];
-                c1 = g.face_cells[2*f + 0];
-                c2 = g.face_cells[2*f + 1];
+                const auto f  = g.cell_faces[i];
+                const auto c1 = g.face_cells[2*f + 0];
+                const auto c2 = g.face_cells[2*f + 1];
 
                 n += (c1 >= 0) && (c2 >= 0);
             }
@@ -145,7 +145,7 @@ namespace Opm {
             connections.reserve  (nconn + 1);
             connections.push_back(c);
 
-            for (int i = g.cell_facepos[c + 0];
+            for (auto i = g.cell_facepos[c + 0];
                  i     < g.cell_facepos[c + 1]; ++i) {
                 int f  = g.cell_faces[i];
                 int c1 = g.face_cells[2*f + 0];
@@ -180,11 +180,11 @@ namespace Opm {
             model_.initResidual(c, F);
             F += ndof;
 
-            for (int i = g.cell_facepos[c + 0];
+            for (auto i = g.cell_facepos[c + 0];
                  i     < g.cell_facepos[c + 1]; ++i) {
-                int f  = g.cell_faces[i];
-                int c1 = g.face_cells[2*f + 0];
-                int c2 = g.face_cells[2*f + 1];
+                auto f  = g.cell_faces[i];
+                auto c1 = g.face_cells[2*f + 0];
+                auto c2 = g.face_cells[2*f + 1];
 
                 if ((c1 >= 0) && (c2 >= 0)) {
                     model_.fluxConnection(state, g, dt, c, f, J1, J2, F);
@@ -212,11 +212,11 @@ namespace Opm {
             sys.matasm().assembleBlock(ndof, c, c, J1);  J1 += ndof2;
 
             // Assemble connection contributions.
-            for (int i = g.cell_facepos[c + 0];
+            for (auto i = g.cell_facepos[c + 0];
                  i     < g.cell_facepos[c + 1]; ++i) {
-                int f  = g.cell_faces[i];
-                int c1 = g.face_cells[2*f + 0];
-                int c2 = g.face_cells[2*f + 1];
+                auto f  = g.cell_faces[i];
+                auto c1 = g.face_cells[2*f + 0];
+                auto c2 = g.face_cells[2*f + 1];
 
                 c2 = (c1 == c) ? c2 : c1;
 
diff --git a/opm/core/transport/implicit/SinglePointUpwindTwoPhase.hpp b/opm/core/transport/implicit/SinglePointUpwindTwoPhase.hpp
index 741331a..0c8fcd8 100644
--- a/opm/core/transport/implicit/SinglePointUpwindTwoPhase.hpp
+++ b/opm/core/transport/implicit/SinglePointUpwindTwoPhase.hpp
@@ -296,7 +296,8 @@ namespace Opm {
                 store_.drho() = fluid_.density(0) - fluid_.density(1);
             }
 
-            for (int c = 0, i = 0; c < g.number_of_cells; ++c) {
+            auto i = grid_size_t(0);
+            for (int c = 0; c < g.number_of_cells; ++c) {
                 for (; i < g.cell_facepos[c + 1]; ++i) {
                     const int f = g.cell_faces[i];
                     const int p = 1 - (g.face_cells[2*f + 0] == c);
@@ -481,7 +482,8 @@ namespace Opm {
                 store_.trans(f) = 0.0;
             }
 
-            for (int c = 0, i = 0; c < g.number_of_cells; ++c) {
+            auto i = grid_size_t(0);
+            for (int c = 0; c < g.number_of_cells; ++c) {
                 for (; i < g.cell_facepos[c + 1]; ++i) {
                     int f = g.cell_faces[i];
 
@@ -666,8 +668,9 @@ namespace Opm {
         computeStaticGravity(const Grid& g) {
 
             const int d = g.dimensions;
+            auto i = grid_size_t(0);
 
-            for (int c = 0, i = 0; c < g.number_of_cells; ++c) {
+            for (int c = 0; c < g.number_of_cells; ++c) {
                 const double* cc = g.cell_centroids + (c * d);
 
                 for (; i < g.cell_facepos[c + 1]; ++i) {
diff --git a/opm/porsol/euler/EulerUpstreamImplicit_impl.hpp b/opm/porsol/euler/EulerUpstreamImplicit_impl.hpp
index 200deb2..9877bf9 100644
--- a/opm/porsol/euler/EulerUpstreamImplicit_impl.hpp
+++ b/opm/porsol/euler/EulerUpstreamImplicit_impl.hpp
@@ -246,12 +246,15 @@ namespace Opm
 
         std::vector<double>     faceflux(numhf);
 
-        for (int c = 0, i = 0; c < cgrid->number_of_cells; ++c){
-            for (; i < cgrid->cell_facepos[c + 1]; ++i) {
-                int f= cgrid->cell_faces[i];
-                double outflux = pressure_sol.outflux(i);
-                double sgn = 2.0*(cgrid->face_cells[2*f + 0] == c) - 1;
-                faceflux[f] = sgn * outflux;
+        {
+            auto i = grid_size_t(0);
+            for (int c = 0; c < cgrid->number_of_cells; ++c){
+                for (; i < cgrid->cell_facepos[c + 1]; ++i) {
+                    int f= cgrid->cell_faces[i];
+                    double outflux = pressure_sol.outflux(i);
+                    double sgn = 2.0*(cgrid->face_cells[2*f + 0] == c) - 1;
+                    faceflux[f] = sgn * outflux;
+                }
             }
         }
         int num_db=direclet_hfaces_.size();