The 6.4L Power Stroke is the most misunderstood diesel Ford ever sold. It followed the notorious 6.0, so it inherited a bad reputation before it turned a wheel, and it left production after only three model years (2008–2010) so it never got the redemption arc the 6.0 eventually earned. The truth is more nuanced than "avoid it." The 6.4 is a genuinely strong-running engine with real, specific weak points and a running-cost profile that scares off a lot of buyers for good reason. Here's the honest version.
What the 6.4 actually is
The 6.4 is an International-built 6.4L V8 with compound (sequential) turbochargers and a high-pressure common-rail fuel system, a big architectural jump from the 6.0's HEUI setup. In stock form it makes roughly 350 horsepower and 650 pound-feet, and it feels stronger than those numbers suggest because the compound turbos build boost early and pull hard up top. It's also the first Power Stroke to carry a diesel particulate filter (DPF), along with EGR. That DPF, and the regeneration strategy Ford used to keep it clean, is at the root of the 6.4's biggest problem.
The weak points, ranked by what actually hurts
Fuel dilution of the engine oil. This is the headline issue. The 6.4 does its DPF regeneration by injecting extra fuel late in the combustion cycle to raise exhaust temperature. Some of that fuel washes past the rings into the crankcase, diluting the oil. On a truck driven in stop-and-go or short trips, regens happen often and the oil can thin out and drop in level control. Short oil-change intervals and highway miles are the defense. Ignore it and you accelerate wear on everything the oil is supposed to protect.
Cracked pistons. The factory pistons are the 6.4's structural ceiling. Stock trucks are generally fine, but the platform responds so well to tuning that owners chase power, and the pistons crack, often at the bowl. If you're shopping a used 6.4, a tuned truck with unknown history is a real gamble. A clean, stock or lightly tuned truck is a much safer buy.
Radiators and cooling. The plastic-tank radiators crack and weep, and coolant work on this engine is not cheap. Budget for it.
Up-pipe gaskets and exhaust leaks. The up-pipes to the turbos use gaskets that leak with heat cycling, and you'll smell and hear it before you find it.
Cost of major work. Many big jobs on the 6.4 are effectively cab-off because access is so tight. That's the real reason people fear this engine: a job that's a weekend on a 7.3 becomes a shop bill on a 6.4. Gaskets, seals, and coolant service add up over time, so a healthy gasket and seal supply and a disciplined maintenance habit matter more here than on almost any other Power Stroke.
Fuel economy. Be realistic. Compound turbos and a DPF do not make an economy engine. Low-to-mid teens is normal, and worse when it's regenerating. If mpg is your priority, the 6.4 is not your truck.
The case for buying one
- It runs hard and sounds great. The compound turbos give it a character no other stock Power Stroke has.
- They're cheap to get into. The reputation keeps purchase prices down, so you can buy a lot of truck for the money.
- A stock, well-maintained 6.4 with documented oil changes is a legitimately good truck. The engine's core is stout when it isn't fighting fuel dilution and isn't over-tuned.
The case for avoiding one
- You drive short trips. Regen-driven fuel dilution punishes short-trip use. This engine wants to run hot and long.
- You can't wrench and don't have a diesel shop you trust. Cab-off labor rates change the math fast.
- The truck is heavily tuned with no records. Cracked-piston risk plus unknown history is how people get burned.
How to buy a used 6.4 the smart way
Pull the oil cap and dipstick and smell for fuel. Check the oil level for being over-full (a dilution tell). Ask for oil-change records and interval history. Cold-start it and watch for excessive smoke and rough running. Look for coolant weeping at the radiator and stains around the up-pipes. Scan for stored codes and ask directly whether it's tuned and what tune is loaded. A stock truck with paperwork beats a "built" truck with a story every time.
Parts you'll need
The 6.4 rewards preventive work: frequent oil and filter changes, cooling-system attention, and staying ahead of gasket leaks before they turn into bigger jobs. Start with quality gaskets and seals for the up-pipes, coolant crossovers, and the routine service points, and browse the full 6.4L Power Stroke parts collection, organized by engine so you confirm fitment for your application.
FAQ
Is the 6.4 Power Stroke reliable? Stock and maintained, it's reliable enough. The failure modes, fuel dilution, cracked pistons under tuning, radiators, and expensive access, are predictable and manageable if you know them going in.
Is the 6.4 better or worse than the 6.0? Different problems. The 6.0 is head studs, EGR coolers, and oil coolers. The 6.4 is fuel dilution, cracked pistons, and cost of access. The 6.4 makes more power stock; the 6.0 is cheaper to work on.
Should I delete the emissions to fix the fuel dilution? No. Removing emissions equipment on an on-road truck is illegal under the Clean Air Act. Manage dilution with short oil intervals and highway miles instead.
Where we land
Buy a 6.4 if it's stock or lightly tuned, has real oil-change records, and you either wrench or have a trusted diesel shop. Avoid it if you drive short trips, need economy, or you're looking at a heavily tuned truck with no history. It's a good engine with a specific owner profile, not a trap and not a bargain-basement 7.3.
Shop 6.4 Power Stroke diesel parts at coredieselparts.com. Free shipping over $70, ships fast.
Related guides: - 6.0 vs 7.3 Power Stroke: Which One Should You Buy - Best Years for a Used Power Stroke