If you’ve read what I wrote about the 6.0L Powerstroke, you’re thinking nothing could be worse than that engine. The 6.0L was a parts-eating, head-gasket-blowing nightmare that took a generation of mechanics to figure out. It made Ford diesel guys hate Ford for ten years.
Then Ford built the 6.4L Powerstroke. From 2008 through 2010. To replace the 6.0.
The 6.4L is worse. I’ll say that twice. It’s worse. Anybody who tells you different either doesn’t work on these or is selling one and praying.
What’s wrong with the 6.4
Where do I start.
Two turbos. Ford put twin sequential turbos on the 6.4. Small high-pressure turbo for low-rpm response, big low-pressure turbo for high-rpm flow. Sounds great. In practice, both turbos are heat-soaked into oblivion by the EGR system, and the small turbo’s variable geometry vanes stick with soot by 80,000 miles. When the small turbo seizes, the big turbo can’t hand off, and you get either no boost or runaway boost. Either way, you’re parked.
Replacement turbo set: $3,500-5,500 from Ford. Aftermarket twin turbo replacement: $2,500-4,000. Labor: $1,200-1,800 either way.
The radiator. Ford put the EGR cooler in line with the regular cooling system. The EGR cooler ruptures internally, fills the cooling system with combustion byproduct, plugs the radiator from the inside, and the engine starts running hot. To fix it you replace the radiator, the EGR cooler, the oil cooler (because it’s plugged too), the thermostat, and flush the entire system. $2,000-3,500 done.
Fuel dilution into the oil. The 6.4 uses post-injection during regeneration cycles to burn off the diesel particulate filter (DPF). Some of that fuel ends up in the oil instead of going out the tailpipe. Oil dilution rises continuously. By 5,000 miles into an oil change interval, the oil is 5-10% diesel fuel. That’s not oil anymore. That’s solvent. Bearings don’t love that. Crankshafts don’t love that. Engines don’t love that.
This is why every diesel guy you talk to who knows the 6.4 says you have to change the oil every 4,000 miles AT MOST. And use a heavy synthetic that’s tolerant of fuel dilution. And monitor your oil level — because dilution adds to the oil level, so the dipstick can read full while the engine’s actually running on contaminated oil.
The DPF and SCR system. Diesel particulate filter, exhaust temperature sensors, NOx sensors, the whole emissions package. All of it fails. Continuously. Replacement DPF: $2,500-4,500. Sensors: $300-600 each. The 6.4 was Ford’s first attempt at meeting 2007 emissions standards with a diesel, and they didn’t really know what they were doing yet.
Head bolts (yes, again). Like the 6.0, the 6.4L doesn’t have enough head bolts for the cylinder pressure. ARP studs are recommended at any sign of head gasket weakness. The good news is the 6.4 doesn’t blow head gaskets quite as readily as the 6.0 did — the architecture is slightly better. The bad news is when it does fail, you’re pulling the cab off because there’s no other way to access the heads on a 6.4 in a Super Duty chassis.
Cab-off head gasket job: $7,000-12,000.
What you’ll see and hear
- Long crank time on cold start
- Black smoke under acceleration (turbo lag plus EGR overload)
- DEF/regen warnings if you drive only short distances (DPF won’t regenerate properly)
- Coolant overflow (EGR cooler getting tired)
- Oil level rising on the dipstick (fuel dilution)
- Power loss, especially under load
- Limp mode warnings
- White smoke at startup that takes a long time to clear
- Whining or hissing from the engine bay (turbo bearing failure)
What it costs to keep one going
Realistic annual maintenance budget on a 6.4L Powerstroke:
- Oil changes every 4,000 miles with full synthetic and a quality filter: $80-120 each, so $400-600/year
- DPF cleaning or replacement somewhere between 80,000 and 150,000 miles
- Turbo replacement somewhere between 100,000 and 180,000 miles
- EGR cooler/radiator replacement once or twice over the truck’s life
- Various sensor replacements continuously
A 6.4L Super Duty over 200,000 miles will cost you more in repairs than the truck cost new.
The “delete” question
Just like with the 6.0L, the diesel community has an answer to all this: EGR delete, DPF delete, DEF delete, custom tune. Eliminates most of the emissions-related failures, gets you back to 18-22 MPG instead of the factory 12-15, and gives the engine its full rated power back.
It’s also a federal emissions violation. Federal enforcement is light. State enforcement in Texas is essentially nonexistent on these trucks. Most every diesel shop in the state will do it. Total cost: $2,500-4,000 for the kit and tune plus install.
I’m not telling you to do it. I’m telling you what’s out there. Make your own call.
Should you buy one?
A 2008-2010 Ford F-250, F-350, or F-450 with the 6.4L Powerstroke is generally NOT a yes. There are exceptions:
- Truck has been deleted properly with a quality kit (Mishimoto, Sinister, MBRP, etc.) and tuned
- Documentation showing recent turbo, DPF, EGR cooler, radiator, oil cooler work
- Owner is willing to take less than retail because they know what they’re selling
- You have a diesel shop you trust and a budget for ongoing maintenance
Hard pass on:
- Stock-emissions 6.4 with no recent work
- Any 6.4 used for short-trip duty (DPF won’t regenerate properly, all the emissions equipment fails faster)
- 6.4 with documented overheating history
- 6.4 with white smoke at startup
If you already own one:
- 4,000 mile oil changes maximum, no exceptions, full synthetic 15W-40 (or 5W-40 if you live where it gets cold)
- Watch oil level monthly, not just at oil changes
- If you’re outside warranty, seriously consider the delete route — the trucks last twice as long
- Find a real diesel shop, not the dealer
- Budget for big repairs annually
The 6.4 was Ford’s emissions panic project. They needed a 2007-compliant diesel and they rushed it. The follow-up engine, the 6.7L Scorpion (2011-plus), was developed in-house by Ford and is night-and-day better. If you’re shopping a Ford diesel from this era, the 6.4 is the year you skip. The 7.3 (1999-2003) is great. The 6.0 is bad but fixable. The 6.4 is the one nobody should have built. The 6.7 is the redemption.
Take the 6.7. Pay more, save in repairs, drive it 300,000 miles, win.