diff --git a/CMakeLists.txt b/CMakeLists.txt
index e741beb1b4..334de77bcf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -166,10 +166,10 @@ opm_add_test(waterair_pvs_ni
              TEST_ARGS --grid-global-refinements=1)
 
 opm_add_test(lens_immiscible_vcfv_ad
-             TEST_ARGS --end-time=3000)
+             TEST_ARGS --end-time=3000 --threads-per-process=1)
 
 opm_add_test(lens_immiscible_vcfv_fd
-             TEST_ARGS --end-time=3000)
+             TEST_ARGS --end-time=3000 --threads-per-process=1)
 
 opm_add_test(lens_immiscible_ecfv_ad
              TEST_ARGS --end-time=3000)
@@ -235,10 +235,10 @@ foreach(tapp co2injection_flash_ni_vcfv
   opm_add_test(${tapp})
 endforeach()
 
-opm_add_test(reservoir_blackoil_vcfv TEST_ARGS --end-time=8750000)
+opm_add_test(reservoir_blackoil_vcfv TEST_ARGS --end-time=8750000 --threads-per-process=1)
 opm_add_test(reservoir_blackoil_ecfv TEST_ARGS --end-time=8750000)
-opm_add_test(reservoir_ncp_vcfv TEST_ARGS --end-time=8750000)
-opm_add_test(reservoir_ncp_ecfv TEST_ARGS --end-time=8750000)
+opm_add_test(reservoir_ncp_vcfv TEST_ARGS --end-time=8750000 --threads-per-process=1)
+opm_add_test(reservoir_ncp_ecfv TEST_ARGS --end-time=8750000 --threads-per-process=1)
 
 opm_add_test(fracture_discretefracture
              CONDITION ${DUNE_ALUGRID_FOUND}
@@ -278,7 +278,7 @@ opm_add_test(lens_immiscible_vcfv_fd_parallel
              PROCESSORS 4
              CONDITION ${MPI_FOUND}
              DRIVER_ARGS --parallel-simulation=4
-             TEST_ARGS --end-time=250 --initial-time-step-size=250)
+             TEST_ARGS --end-time=250 --initial-time-step-size=250 --threads-per-process=1)
 
 opm_add_test(lens_immiscible_vcfv_ad_parallel
              EXE_NAME lens_immiscible_vcfv_ad
@@ -286,7 +286,7 @@ opm_add_test(lens_immiscible_vcfv_ad_parallel
              PROCESSORS 4
              CONDITION ${MPI_FOUND}
              DRIVER_ARGS --parallel-simulation=4
-             TEST_ARGS --end-time=250 --initial-time-step-size=250)
+             TEST_ARGS --end-time=250 --initial-time-step-size=250 --threads-per-process=1)
 
 opm_add_test(lens_immiscible_ecfv_ad_parallel
              EXE_NAME lens_immiscible_ecfv_ad
diff --git a/ewoms/disc/common/fvbasediscretization.hh b/ewoms/disc/common/fvbasediscretization.hh
index 9178aea2fe..bcd8a7a7fc 100644
--- a/ewoms/disc/common/fvbasediscretization.hh
+++ b/ewoms/disc/common/fvbasediscretization.hh
@@ -209,7 +209,7 @@ SET_TYPE_PROP(FvBaseDiscretization, ConstraintsContext, Ewoms::FvBaseConstraints
  * \brief The OpenMP threads manager
  */
 SET_TYPE_PROP(FvBaseDiscretization, ThreadManager, Ewoms::ThreadManager<TypeTag>);
-SET_INT_PROP(FvBaseDiscretization, ThreadsPerProcess, 1);
+SET_INT_PROP(FvBaseDiscretization, ThreadsPerProcess, -1);
 SET_BOOL_PROP(FvBaseDiscretization, UseLinearizationLock, true);
 
 /*!
diff --git a/ewoms/parallel/threadmanager.hh b/ewoms/parallel/threadmanager.hh
index d53503646b..b407eb1d3d 100644
--- a/ewoms/parallel/threadmanager.hh
+++ b/ewoms/parallel/threadmanager.hh
@@ -100,6 +100,12 @@ public:
         // used in the end.
         if (numThreads_ > 0)
             omp_set_num_threads(numThreads_);
+        else {
+            if (!getenv("OMP_NUM_THREADS")) {
+                int num_core = omp_get_num_procs();
+                omp_set_num_threads(std::min(2, num_core));
+            }
+        }
 
         numThreads_ = omp_get_max_threads();
 #endif