6.4 Vs. 6.7 Power Stroke: How Do The Diesel Engines Compare?

The 6.4- and 6.7-liter Power Stroke turbo diesel engines are two different versions of the Ford Power Stroke engine, used to power Ford's big Super Duty trucks at various points. Both engines use high-pressure common rail fuel systems and turbocharged induction, although the two engines evolved through different processes. They both deserve a bit of unique attention, too. Before we get into the history of the two engines, we'll compare some specs.

The stock 6.4-liter Power Stroke produced 350 horsepower and 650 lb-ft of torque. While those numbers were an improvement compared to its predecessor (the 6.0-liter Power Stroke), the 6.7 Power Stroke quickly surpassed the 6.4. Naturally, the 6.7-liter engine has more displacement. And when the 6.7 Power Stroke was first introduced, it produced 390 hp and 735 lb-ft. These were big gains over the 6.4, along with updates introduced by Ford like a new engine block, new cylinder heads, and piston-cooling jets for longer engine life.

Soon after the 6.7's introduction, Ford issued an engine software upgrade that increased existing and new 6.7 Power Strokes to 400 hp and 800 lb-ft – presumably in response to better power numbers posted by the latest Duramax diesel engine used by GM. The 6.7 Power Stroke has continued to increase its power output over the past 15 years, and it is still the only diesel engine available in Ford F-Series Super Duty pickup trucks. For 2026, the power levels are much higher: the latest High Output 6.7 Power Stroke is rated at 500 hp and 1,200 lb-ft.

There have been four Power Stroke variations and displacements over the years: 7.3, 6.0, 6.4, and 6.7. And all but one of those engines was built by Navistar International. Ford introduced the Power Stroke diesel engine in 1994 with the release of the refreshed 7.3-liter Turbo Diesel built by Navistar International. While Ford 7.3 Power Stroke owners report some common problems, the original Power Stroke is highly prized among diesel truck enthusiasts.

Tensions between Ford and Navistar began with problems surrounding the 6.0 Power Stroke that replaced the 7.3. The 6.0-liter engine had design issues that would eventually land Ford in hot legal water, and land it amongst your least-favorite engines, but the problems didn't stop with the 6.0. Ford claimed high costs for repairing and replacing the 6.0-liter engine, and began deducting warranty costs from what it paid Navistar for the new 6.4 Power Stroke engines it provided. That deduction would eventually lead to a temporary shutdown of Navistar's 6.4 Power Stroke assembly. 

Despite the dispute, Ford used the Navistar-built 6.4 Power Stroke in its 2008 to 2010 model year Super Duty pickups, but that engine had significant problems, too. Ultimately, the problems surrounding Navistar-built Power Stroke engines prompted Ford to ditch Navistar and bring Power Stroke production in-house with the design and build of the 6.7 Power Stroke. The 6.7 Power Stroke is the only Ford Power Stroke with a history that doesn't include Navistar International. Ford describes its current Power Stroke, first introduced in the 2011 F-Series Super Duty, as "an all-new, built-from-scratch, state-of-the-art 6.7L Power Stroke® diesel."