Using search to display entries based on a value in a number field I'm trying to return results based on a year stored in a custom field. For example, returning entries with a model year greater than 2006 and less than 2009. Is there a search syntax to support this?

For example: for entry in craft.entries.section('equipment').search(modelYear: &gt; 2006 &amp;&amp; &lt; 2009) …
You can do a certain amount of logic in the ElementCriteriaModel syntax. I think this will work:

{% set entries = craft.entries.section('equipment').modelYear('and, &gt; 2006, &lt; 2009') %}
{% for entry in entries %}
  ...
{% endfor %}