If you’re shopping for a used Chevrolet Silverado HD or GMC Sierra HD, you’ve probably come across plenty of discussions about the L5P Duramax. Buyers frequently search for terms like “L5P years,” “best L5P year,” or “L5P Duramax reliability” because they want to know whether certain model years are better than others before making a significant investment.

The good news is that the L5P has earned one of the strongest reputations of any modern heavy-duty diesel platform. Unlike some earlier diesel engines that developed well-known “years to avoid,” the L5P has remained remarkably consistent since its introduction. That doesn’t mean every used truck is identical, but it does mean buyers should spend less time worrying about a specific calendar year and more time evaluating the individual truck.

In this guide, we’ll explain what changed throughout the L5P’s production run, discuss common reliability questions, compare various model years, and help you decide what to look for when shopping for a used L5P Duramax.