diff --git a/lib/modules/manager/mix/index.ts b/lib/modules/manager/mix/index.ts
index e9722265580591..df1fa52ec6cf6d 100644
--- a/lib/modules/manager/mix/index.ts
+++ b/lib/modules/manager/mix/index.ts
@@ -5,6 +5,7 @@ import { HexDatasource } from '../../datasource/hex';
 
 export { extractPackageFile } from './extract';
 export { updateArtifacts } from './artifacts';
+export { getRangeStrategy } from './range';
 
 export const url = 'https://hexdocs.pm/mix/Mix.html';
 export const categories: Category[] = ['elixir'];
diff --git a/lib/modules/manager/mix/range.spec.ts b/lib/modules/manager/mix/range.spec.ts
new file mode 100644
index 00000000000000..3b0ff9a3468637
--- /dev/null
+++ b/lib/modules/manager/mix/range.spec.ts
@@ -0,0 +1,48 @@
+import type { RangeConfig } from '../types';
+import { getRangeStrategy } from '.';
+
+describe('modules/manager/mix/range', () => {
+  it('returns same if not auto', () => {
+    const config: RangeConfig = { rangeStrategy: 'pin' };
+    expect(getRangeStrategy(config)).toBe('pin');
+
+    config.rangeStrategy = 'widen';
+    expect(getRangeStrategy(config)).toBe('widen');
+  });
+
+  it('widens complex bump', () => {
+    const config: RangeConfig = {
+      rangeStrategy: 'bump',
+      depType: 'prod',
+      currentValue: '>= 1.6.0 and < 2.0.0',
+    };
+    expect(getRangeStrategy(config)).toBe('widen');
+  });
+
+  it('bumps non-complex bump', () => {
+    const config: RangeConfig = {
+      rangeStrategy: 'bump',
+      depType: 'prod',
+      currentValue: '~>1.0.0',
+    };
+    expect(getRangeStrategy(config)).toBe('bump');
+  });
+
+  it('widens complex auto', () => {
+    const config: RangeConfig = {
+      rangeStrategy: 'auto',
+      depType: 'prod',
+      currentValue: '<1.7.0 or ~>1.7.1',
+    };
+    expect(getRangeStrategy(config)).toBe('widen');
+  });
+
+  it('defaults to update-lockfile', () => {
+    const config: RangeConfig = {
+      rangeStrategy: 'auto',
+      depType: 'prod',
+    };
+    expect(getRangeStrategy(config)).toBe('update-lockfile');
+  });
+});
+
diff --git a/lib/modules/manager/mix/range.ts b/lib/modules/manager/mix/range.ts
new file mode 100644
index 00000000000000..4d6e563eb5123e
--- /dev/null
+++ b/lib/modules/manager/mix/range.ts
@@ -0,0 +1,26 @@
+import { parseRange } from 'semver-utils';
+import { logger } from '../../../logger';
+import type { RangeStrategy } from '../../../types';
+import type { RangeConfig } from '../types';
+
+export function getRangeStrategy(config: RangeConfig): RangeStrategy {
+  const { currentValue, rangeStrategy } = config;
+  const isComplexRange = currentValue
+    ? parseRange(currentValue).length > 1
+    : false;
+
+  if (rangeStrategy === 'bump' && isComplexRange) {
+    logger.debug(
+      { currentValue },
+      'Replacing bump strategy for complex range with widen',
+    );
+    return 'widen';
+  }
+  if (rangeStrategy !== 'auto') {
+    return rangeStrategy;
+  }
+  if (isComplexRange) {
+    return 'widen';
+  }
+  return 'update-lockfile';
+}
diff --git a/lib/modules/manager/mix/readme.md b/lib/modules/manager/mix/readme.md
index 175d75a9003123..7924c9704caa2e 100644
--- a/lib/modules/manager/mix/readme.md
+++ b/lib/modules/manager/mix/readme.md
@@ -6,3 +6,22 @@ The following `depTypes` are currently supported by the `mix` manager :
 
 - `prod`: all dependencies by default
 - `dev`: dependencies with [`:only` option](https://hexdocs.pm/mix/Mix.Tasks.Deps.html#module-dependency-definition-options) not containing `:prod`
+
+### Default `rangeStrategy=auto` behavior
+
+Renovate's default [`rangeStrategy`](../../../configuration-options.md#rangestrategy) is `"auto"`.
+Here's how `"auto"` works with the `mix` manager:
+
+| Version type             | New version | Old range             | New range after update | What Renovate does                                                        |
+| :----------------------- | :---------- | :-------------------- | :--------------------- | :------------------------------------------------------------------------ |
+| Complex range            | `1.7.2`     | `< 1.7.0 or ~> 1.7.1` | `< 1.7.0 or ~> 1.7.2`  | Widen range to include the new version.                                   |
+| Simple range             | `0.39.0`    | `<= 0.38.0`           | `<= 0.39.0`            | If update outside current range: widens range to include the new version. |
+| Exact version constraint | `0.13.0`    | `== 0.12.0`           | `== 0.13.0`            | Replace old version with new version.                                     |
+
+### Recommended `rangeStrategy` for apps and libraries
+
+For applications, we recommend using `rangeStrategy=pin`.
+This pins your dependencies to exact versions, which is generally considered [best practice for apps](../../../dependency-pinning.md).
+
+For libraries, use `rangeStrategy=widen` with version ranges in your `mix.exs`.
+This allows for greater compatibility with other projects that may use your library as a dependency.