diff --git a/src/benchmarks/micro/libraries/CommonUtils/PerfUtils.cs b/src/benchmarks/micro/libraries/CommonUtils/PerfUtils.cs
index 1464e7370f2..630ecd967c7 100644
--- a/src/benchmarks/micro/libraries/CommonUtils/PerfUtils.cs
+++ b/src/benchmarks/micro/libraries/CommonUtils/PerfUtils.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.IO;
+using System.Linq;
 
 namespace System
 {
@@ -31,5 +32,15 @@ public static string CreateString(int length)
 
             return new string(str);
         }
+
+        /// <summary>
+        /// Helper method to create a string containing random alphanumeric
+        /// characters equal to the specified length
+        /// </summary>
+        public static string CreateRandomString(int length, string alphabet = "abcdefghijklmnopqrstuvwxyz0123456789", int seed = 42)
+        {
+            Random random = new(seed);  // use the given seed, to make the benchmarks repeatable
+            return new string(Enumerable.Repeat(alphabet, length).Select(s => s[random.Next(s.Length)]).ToArray());
+        }
     }
 }
diff --git a/src/benchmarks/micro/libraries/System.Runtime/Perf.String.cs b/src/benchmarks/micro/libraries/System.Runtime/Perf.String.cs
index 28e8bd0b037..4a4646e7c61 100644
--- a/src/benchmarks/micro/libraries/System.Runtime/Perf.String.cs
+++ b/src/benchmarks/micro/libraries/System.Runtime/Perf.String.cs
@@ -154,13 +154,20 @@ public string TrimEnd_CharArr(string s, char[] c)
             => s.TrimEnd(c);
 
         [Benchmark]
-        [Arguments("Hello", 'l', '!')] // Contains two 'l'
-        [Arguments("Hello", 'a', 'b')] // Contains one 'a'
-        [Arguments("This is a very nice sentence", 'z', 'y')] // 'z' does not exist in the string
-        [Arguments("This is a very nice sentence", 'i', 'I')] // 'i' occuress 3 times in the string
+        [ArgumentsSource(nameof(ReplaceArguments))]
         public string Replace_Char(string text, char oldChar, char newChar)
             => text.Replace(oldChar, newChar);
 
+        public static IEnumerable<object[]> ReplaceArguments()
+        {
+            yield return new object[] { "Hello", 'l', '!' };    // Contains two 'l'
+            yield return new object[] { "Hello", 'a', 'b' };    // Contains one 'a'
+            yield return new object[] { "This is a very nice sentence", 'z', 'y' }; // 'z' does not exist in the string
+            yield return new object[] { "This is a very nice sentence", 'i', 'I' }; // 'i' occurs 3 times in the string
+            yield return new object[] { PerfUtils.CreateRandomString(100, seed: 42), 'b', '+' };    // b occurs 8 times in the string
+            yield return new object[] { PerfUtils.CreateRandomString(1000, seed: 42), 'b', '+' };   // b occurs 42 times in the string
+        }
+
         [Benchmark]
         [Arguments("This is a very nice sentence", "bad", "nice")] // there are no "bad" words in the string
         [Arguments("This is a very nice sentence", "nice", "bad")] // there are is one "nice" word in the string