diff --git a/dev/devicelab/bin/tasks/hot_mode_dev_cycle__preview_dart_2_benchmark.dart b/dev/devicelab/bin/tasks/hot_mode_dev_cycle__benchmark_dart1.dart
similarity index 86%
rename from dev/devicelab/bin/tasks/hot_mode_dev_cycle__preview_dart_2_benchmark.dart
rename to dev/devicelab/bin/tasks/hot_mode_dev_cycle__benchmark_dart1.dart
index e50d8f1df90..4d9767565be 100644
--- a/dev/devicelab/bin/tasks/hot_mode_dev_cycle__preview_dart_2_benchmark.dart
+++ b/dev/devicelab/bin/tasks/hot_mode_dev_cycle__benchmark_dart1.dart
@@ -8,5 +8,5 @@ import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 
 Future<Null> main() async {
-  await task(createHotModeTest(isPreviewDart2: true));
+  await task(createHotModeTest(isPreviewDart2: false));
 }
diff --git a/dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios__preview_dart_2_benchmark.dart b/dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios__benchmark_dart1.dart
similarity index 89%
rename from dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios__preview_dart_2_benchmark.dart
rename to dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios__benchmark_dart1.dart
index e400000020d..99c70d710e4 100644
--- a/dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios__preview_dart_2_benchmark.dart
+++ b/dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios__benchmark_dart1.dart
@@ -10,5 +10,5 @@ import 'package:flutter_devicelab/framework/adb.dart';
 
 Future<Null> main() async {
   deviceOperatingSystem = DeviceOperatingSystem.ios;
-  await task(createHotModeTest(isPreviewDart2: true));
+  await task(createHotModeTest(isPreviewDart2: false));
 }
diff --git a/dev/devicelab/lib/tasks/hot_mode_tests.dart b/dev/devicelab/lib/tasks/hot_mode_tests.dart
index cb929d835d9..e82192c068a 100644
--- a/dev/devicelab/lib/tasks/hot_mode_tests.dart
+++ b/dev/devicelab/lib/tasks/hot_mode_tests.dart
@@ -16,7 +16,7 @@ import '../framework/utils.dart';
 final Directory _editedFlutterGalleryDir = dir(path.join(Directory.systemTemp.path, 'edited_flutter_gallery'));
 final Directory flutterGalleryDir = dir(path.join(flutterDirectory.path, 'examples/flutter_gallery'));
 
-TaskFunction createHotModeTest({ bool isPreviewDart2: false }) {
+TaskFunction createHotModeTest({ bool isPreviewDart2: true }) {
   return () async {
     final Device device = await devices.workingDevice;
     await device.unlock();
@@ -27,6 +27,8 @@ TaskFunction createHotModeTest({ bool isPreviewDart2: false }) {
     ];
     if (isPreviewDart2)
       options.add('--preview-dart-2');
+    else
+      options.add('--no-preview-dart-2');
     setLocalEngineOptionIfNecessary(options);
     int hotReloadCount = 0;
     Map<String, dynamic> twoReloadsData;
diff --git a/dev/devicelab/lib/tasks/microbenchmarks.dart b/dev/devicelab/lib/tasks/microbenchmarks.dart
index 7558a4dcef4..81dd71ed7a8 100644
--- a/dev/devicelab/lib/tasks/microbenchmarks.dart
+++ b/dev/devicelab/lib/tasks/microbenchmarks.dart
@@ -23,7 +23,7 @@ TaskFunction createMicrobenchmarkTask() {
     final Device device = await devices.workingDevice;
     await device.unlock();
 
-    Future<Map<String, double>> _runMicrobench(String benchmarkPath, {bool previewDart2: false}) async {
+    Future<Map<String, double>> _runMicrobench(String benchmarkPath, {bool previewDart2: true}) async {
       Future<Map<String, double>> _run() async {
         print('Running $benchmarkPath');
         final Directory appDir = dir(
@@ -40,6 +40,8 @@ TaskFunction createMicrobenchmarkTask() {
           ];
           if (previewDart2)
             options.add('--preview-dart-2');
+          else
+            options.add('--no-preview-dart-2');
           setLocalEngineOptionIfNecessary(options);
           options.add(benchmarkPath);
           return await _startFlutter(
@@ -59,33 +61,26 @@ TaskFunction createMicrobenchmarkTask() {
     allResults.addAll(await _runMicrobench('lib/gestures/velocity_tracker_bench.dart'));
     allResults.addAll(await _runMicrobench('lib/stocks/animation_bench.dart'));
 
-    // Run micro-benchmarks once again in --preview-dart-2 mode.
-    // Append "_dart2" suffix to the result keys to distinguish them from
+    // Run micro-benchmarks once again in --no-preview-dart-2 mode.
+    // Append "_dart1" suffix to the result keys to distinguish them from
     // the original results.
 
-    void addDart2Results(Map<String, double> benchmarkResults) {
+    void addDart1Results(Map<String, double> benchmarkResults) {
       benchmarkResults.forEach((String key, double result) {
-        allResults[key + '_dart2'] = result;
+        allResults[key + '_dart1'] = result;
       });
     }
 
-    try {
-      addDart2Results(await _runMicrobench(
-          'lib/stocks/layout_bench.dart', previewDart2: true));
-      addDart2Results(await _runMicrobench(
-          'lib/stocks/layout_bench.dart', previewDart2: true));
-      addDart2Results(await _runMicrobench(
-          'lib/stocks/build_bench.dart', previewDart2: true));
-      addDart2Results(await _runMicrobench(
-          'lib/gestures/velocity_tracker_bench.dart', previewDart2: true));
-      addDart2Results(await _runMicrobench(
-          'lib/stocks/animation_bench.dart', previewDart2: true));
-    } catch (e) {
-      // Ignore any exceptions from running benchmarks in Dart 2.0 mode,
-      // as these benchmarks are considered flaky.
-      stderr.writeln('WARNING: microbenchmarks FAILED in --preview-dart-2 mode.');
-    }
-
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/layout_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/layout_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/build_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/gestures/velocity_tracker_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/animation_bench.dart', previewDart2: false));
     return new TaskResult.success(allResults, benchmarkScoreKeys: allResults.keys.toList());
   };
 }
diff --git a/dev/devicelab/lib/tasks/perf_tests.dart b/dev/devicelab/lib/tasks/perf_tests.dart
index cdd209e56cf..7494aa973be 100644
--- a/dev/devicelab/lib/tasks/perf_tests.dart
+++ b/dev/devicelab/lib/tasks/perf_tests.dart
@@ -199,9 +199,9 @@ class CompileTest {
         ..addAll(await _compileAot())
         ..addAll(await _compileApp())
         ..addAll(await _compileDebug())
-        ..addAll(_suffix(await _compileAot(previewDart2: true), '__preview_dart_2'))
-        ..addAll(_suffix(await _compileApp(previewDart2: true), '__preview_dart_2'))
-        ..addAll(_suffix(await _compileDebug(previewDart2: true), '__preview_dart_2'));
+        ..addAll(_suffix(await _compileAot(previewDart2: false), '__dart1'))
+        ..addAll(_suffix(await _compileApp(previewDart2: false), '__dart1'))
+        ..addAll(_suffix(await _compileDebug(previewDart2: false), '__dart1'));
 
       return new TaskResult.success(metrics, benchmarkScoreKeys: metrics.keys.toList());
     });
@@ -214,7 +214,7 @@ class CompileTest {
     );
   }
 
-  static Future<Map<String, dynamic>> _compileAot({ bool previewDart2: false }) async {
+  static Future<Map<String, dynamic>> _compileAot({ bool previewDart2: true }) async {
     // Generate blobs instead of assembly.
     await flutter('clean');
     final Stopwatch watch = new Stopwatch()..start();
@@ -235,6 +235,8 @@ class CompileTest {
     }
     if (previewDart2)
       options.add('--preview-dart-2');
+    else
+      options.add('--no-preview-dart-2');
     setLocalEngineOptionIfNecessary(options);
     final String compileLog = await evalFlutter('build', options: options);
     watch.stop();
@@ -249,7 +251,7 @@ class CompileTest {
     return metrics;
   }
 
-  static Future<Map<String, dynamic>> _compileApp({ bool previewDart2: false }) async {
+  static Future<Map<String, dynamic>> _compileApp({ bool previewDart2: true }) async {
     await flutter('clean');
     final Stopwatch watch = new Stopwatch();
     int releaseSizeInBytes;
@@ -288,7 +290,7 @@ class CompileTest {
     };
   }
 
-  static Future<Map<String, dynamic>> _compileDebug({ bool previewDart2: false }) async {
+  static Future<Map<String, dynamic>> _compileDebug({ bool previewDart2: true }) async {
     await flutter('clean');
     final Stopwatch watch = new Stopwatch();
     final List<String> options = <String>['--debug'];
diff --git a/dev/devicelab/manifest.yaml b/dev/devicelab/manifest.yaml
index 69733ccf5e8..4fb4ebb9302 100644
--- a/dev/devicelab/manifest.yaml
+++ b/dev/devicelab/manifest.yaml
@@ -148,17 +148,17 @@ tasks:
     stage: devicelab
     required_agent_capabilities: ["mac/android"]
 
-  hot_mode_dev_cycle__preview_dart_2_benchmark:
+  hot_mode_dev_cycle__benchmark_dart1:
     description: >
       Measures the performance of Dart VM hot patching feature under
-      --preview-dart-2 option, that enables Dart 2.0 frontend.
+      --no-preview-dart-2 option, that disables Dart 2.0 frontend.
     stage: devicelab
     required_agent_capabilities: ["mac/android"]
 
-  hot_mode_dev_cycle_ios__preview_dart_2_benchmark:
+  hot_mode_dev_cycle_ios__benchmark_dart1:
     description: >
       Measures the performance of Dart VM hot patching feature under
-      --preview-dart-2 option, that enables Dart 2.0 frontend.
+      --no-preview-dart-2 option, that disables Dart 2.0 frontend.
     stage: devicelab_ios
     required_agent_capabilities: ["mac/ios"]
     flaky: true