diff --git a/modules/core/ingest-api/src/main/java/com/lingniu/ingest/api/event/TelemetryMetadataValues.java b/modules/core/ingest-api/src/main/java/com/lingniu/ingest/api/event/TelemetryMetadataValues.java
new file mode 100644
index 00000000..48f85bba
--- /dev/null
+++ b/modules/core/ingest-api/src/main/java/com/lingniu/ingest/api/event/TelemetryMetadataValues.java
@@ -0,0 +1,22 @@
+package com.lingniu.ingest.api.event;
+
+import java.util.Locale;
+
+/**
+ * Stable string formatting for metadata values shared across protocol mappers.
+ */
+public final class TelemetryMetadataValues {
+
+    private TelemetryMetadataValues() {
+    }
+
+    public static String doubleValue(double value) {
+        if (!Double.isFinite(value)) {
+            return "";
+        }
+        String formatted = String.format(Locale.ROOT, "%.6f", value);
+        return formatted.indexOf('.') < 0
+                ? formatted
+                : formatted.replaceAll("0+$", "").replaceAll("\\.$", "");
+    }
+}
diff --git a/modules/core/ingest-api/src/test/java/com/lingniu/ingest/api/event/TelemetryMetadataValuesTest.java b/modules/core/ingest-api/src/test/java/com/lingniu/ingest/api/event/TelemetryMetadataValuesTest.java
new file mode 100644
index 00000000..d19abfc6
--- /dev/null
+++ b/modules/core/ingest-api/src/test/java/com/lingniu/ingest/api/event/TelemetryMetadataValuesTest.java
@@ -0,0 +1,23 @@
+package com.lingniu.ingest.api.event;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class TelemetryMetadataValuesTest {
+
+    @Test
+    void formatsDoubleWithoutFloatingPointNoise() {
+        assertThat(TelemetryMetadataValues.doubleValue(123456.70000000001)).isEqualTo("123456.7");
+        assertThat(TelemetryMetadataValues.doubleValue(1234.5)).isEqualTo("1234.5");
+        assertThat(TelemetryMetadataValues.doubleValue(1234.0)).isEqualTo("1234");
+        assertThat(TelemetryMetadataValues.doubleValue(1.23456789)).isEqualTo("1.234568");
+    }
+
+    @Test
+    void rejectsNonFiniteDoubleValuesAsBlankMetadata() {
+        assertThat(TelemetryMetadataValues.doubleValue(Double.NaN)).isEmpty();
+        assertThat(TelemetryMetadataValues.doubleValue(Double.POSITIVE_INFINITY)).isEmpty();
+        assertThat(TelemetryMetadataValues.doubleValue(Double.NEGATIVE_INFINITY)).isEmpty();
+    }
+}
diff --git a/modules/inbound/inbound-mqtt/src/main/java/com/lingniu/ingest/inbound/mqtt/mapper/YutongEventMapper.java b/modules/inbound/inbound-mqtt/src/main/java/com/lingniu/ingest/inbound/mqtt/mapper/YutongEventMapper.java
index 93d001a3..b8537222 100644
--- a/modules/inbound/inbound-mqtt/src/main/java/com/lingniu/ingest/inbound/mqtt/mapper/YutongEventMapper.java
+++ b/modules/inbound/inbound-mqtt/src/main/java/com/lingniu/ingest/inbound/mqtt/mapper/YutongEventMapper.java
@@ -4,6 +4,7 @@ import com.fasterxml.jackson.databind.JsonNode;
 import com.lingniu.ingest.api.ProtocolId;
 import com.lingniu.ingest.api.event.LocationPayload;
 import com.lingniu.ingest.api.event.RealtimePayload;
+import com.lingniu.ingest.api.event.TelemetryMetadataValues;
 import com.lingniu.ingest.api.event.VehicleEvent;
 import com.lingniu.ingest.api.spi.EventMapper;
 import com.lingniu.ingest.identity.VehicleIdentity;
@@ -16,7 +17,6 @@ import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Base64;
 import java.util.List;
-import java.util.Locale;
 import java.util.Map;
 import java.util.UUID;
 
@@ -99,7 +99,7 @@ public final class YutongEventMapper implements EventMapper<MqttPayload> {
                     0, 0);
             Map<String, String> locationMeta = mileage == null
                     ? meta
-                    : withMeta(meta, "total_mileage_km", formatDouble(mileage));
+                    : withMeta(meta, "total_mileage_km", TelemetryMetadataValues.doubleValue(mileage));
             out.add(new VehicleEvent.Location(
                     UUID.randomUUID().toString(),
                     vin, ProtocolId.MQTT_YUTONG, payload.deviceTime(), ingestTime,
@@ -237,13 +237,6 @@ public final class YutongEventMapper implements EventMapper<MqttPayload> {
         }
     }
 
-    private static String formatDouble(double value) {
-        String formatted = String.format(Locale.ROOT, "%.6f", value);
-        return formatted.indexOf('.') < 0
-                ? formatted
-                : formatted.replaceAll("0+$", "").replaceAll("\\.$", "");
-    }
-
     private record IdentityResolution(VehicleIdentity identity, String errorMessage) {
         private static IdentityResolution ok(VehicleIdentity identity) {
             return new IdentityResolution(identity, null);
diff --git a/modules/protocols/protocol-gb32960/src/main/java/com/lingniu/ingest/protocol/gb32960/mapper/Gb32960EventMapper.java b/modules/protocols/protocol-gb32960/src/main/java/com/lingniu/ingest/protocol/gb32960/mapper/Gb32960EventMapper.java
index b2f5a864..f0ea087f 100644
--- a/modules/protocols/protocol-gb32960/src/main/java/com/lingniu/ingest/protocol/gb32960/mapper/Gb32960EventMapper.java
+++ b/modules/protocols/protocol-gb32960/src/main/java/com/lingniu/ingest/protocol/gb32960/mapper/Gb32960EventMapper.java
@@ -4,6 +4,7 @@ import com.lingniu.ingest.api.ProtocolId;
 import com.lingniu.ingest.api.event.AlarmPayload;
 import com.lingniu.ingest.api.event.LocationPayload;
 import com.lingniu.ingest.api.event.RealtimePayload;
+import com.lingniu.ingest.api.event.TelemetryMetadataValues;
 import com.lingniu.ingest.api.event.VehicleEvent;
 import com.lingniu.ingest.api.spi.EventMapper;
 import com.lingniu.ingest.protocol.gb32960.model.CommandBody;
@@ -16,7 +17,6 @@ import java.time.Instant;
 import java.util.ArrayList;
 import java.util.LinkedHashSet;
 import java.util.List;
-import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.UUID;
@@ -166,7 +166,7 @@ public final class Gb32960EventMapper implements EventMapper<Gb32960Message> {
                     v != null && v.speedKmh != null ? v.speedKmh : 0.0,
                     0.0, 0, p.statusFlag);
             Map<String, String> locationMeta = v != null && v.totalMileageKm != null
-                    ? withMeta(meta, "total_mileage_km", formatDouble(v.totalMileageKm))
+                    ? withMeta(meta, "total_mileage_km", TelemetryMetadataValues.doubleValue(v.totalMileageKm))
                     : meta;
             out.add(new VehicleEvent.Location(
                     UUID.randomUUID().toString(),
@@ -341,10 +341,4 @@ public final class Gb32960EventMapper implements EventMapper<Gb32960Message> {
         return Map.copyOf(copy);
     }
 
-    private static String formatDouble(double value) {
-        String formatted = String.format(Locale.ROOT, "%.6f", value);
-        return formatted.indexOf('.') < 0
-                ? formatted
-                : formatted.replaceAll("0+$", "").replaceAll("\\.$", "");
-    }
 }
diff --git a/modules/protocols/protocol-jt808/src/main/java/com/lingniu/ingest/protocol/jt808/mapper/Jt808EventMapper.java b/modules/protocols/protocol-jt808/src/main/java/com/lingniu/ingest/protocol/jt808/mapper/Jt808EventMapper.java
index 0fba341d..d336762b 100644
--- a/modules/protocols/protocol-jt808/src/main/java/com/lingniu/ingest/protocol/jt808/mapper/Jt808EventMapper.java
+++ b/modules/protocols/protocol-jt808/src/main/java/com/lingniu/ingest/protocol/jt808/mapper/Jt808EventMapper.java
@@ -2,6 +2,7 @@ package com.lingniu.ingest.protocol.jt808.mapper;
 
 import com.lingniu.ingest.api.ProtocolId;
 import com.lingniu.ingest.api.event.LocationPayload;
+import com.lingniu.ingest.api.event.TelemetryMetadataValues;
 import com.lingniu.ingest.api.event.VehicleEvent;
 import com.lingniu.ingest.api.spi.EventMapper;
 import com.lingniu.ingest.identity.VehicleIdentity;
@@ -287,7 +288,7 @@ public final class Jt808EventMapper implements EventMapper<Jt808Message> {
             copy.putAll(Jt808LocationAdditionalInfo.decode(loc.extensionItems()));
             Double totalMileageKm = totalMileageKm(loc);
             if (totalMileageKm != null) {
-                copy.put("total_mileage_km", Double.toString(totalMileageKm));
+                copy.put("total_mileage_km", TelemetryMetadataValues.doubleValue(totalMileageKm));
             }
         }
         return Map.copyOf(copy);