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The Absolute Worst Used Diesel Trucks Ever Made

These are the rigs to avoid if you’re looking for a used diesel truck.

Updated May 28, 2018

Everyone’s seen a Ford with a bumper sticker of Calvin Hobbes taking a whiz on the Cummins emblem. Diesel truck owners are a proud bunch that swear their trucks are the best. But not all diesel trucks are created equal. There are some real Junkers out there – even if the owners don’t want to admit it. Before you get conned into buying someone else’s compression-ignited nightmare, check out this list. These are the rigs you’ll want to avoid if you’re looking for a used diesel truck.


Chevy and GMC C/K pickup 5.7L (1978-1981)

GM’s 5.7L diesel can be found in your grandpa’s Oldsmobile, and it can also be found in Chevy and GMC pickup trucks. The 5.7L diesel was basically a gas 5.7L converted into a diesel. This sounds like a bad idea – and it is. All kinds of problems plague this old oil burner, including faulty head bolts. Weak torque to yield bolts paired with an extremely high compression ratio, cause the cylinder heads to lift off the block. And levitating cylinder heads are bad business. Sure, vintage diesel trucks can be cool, but stay away from 5.7L diesel-equipped rigs.


Chevy and GMC C/K pickup 6.2L (1982-1993)

After the 5.7L diesel debacle, GM realized it should get out of the diesel-building business. So, it hired engine maker, Detroit, to build its next diesel power plant. The result was the uneconomical and anemic 6.2L diesel.  Although it’s the size of a VW bug, the huge naturally aspirated engine makes very little power. The original 6.2L make 130 hp, which is only 40 more ponies than a modern Smart car. The 6.2L also has the tendency to dump oil from its rear main seal – a costly repair that involves removing the transmission.


Chevy and GMC C/K pickup 6.5L (1994-2001)

Most 6.5L engines are turbocharged, which gives them an edge over the feeble 6.2L. Even so, the Detroit built 6.5L can’t compete with same era Cummins and Powerstroke engines. While the other diesel engines were being fitted with direct injection, the 6.5L hobbled along with indirect injection. At its best, the 6.5L makes 180 and 360 lb-ft. Compare that with a Powerstroke-equipped Ford of the same vintage, making up to 275 hp, and it’s easy to see the GM 6.5L is outclassed.

Besides the glaring lack of power, the 6.5L is riddled with mechanical problems. One of the most common issues is failure of the pump-mounted driver. This unit is used to supply power to the fuel solenoid. When it fails, it can cause all kinds of problems from a no-start condition to stalling. The lesson: save your pennies and buy a Duramax.


Ford Super Duty 6.0L (2003-2007)

Introduced mid-2003, the Ford 6.0L turbo is by far the worst modern diesel engine. It’s so bad, in fact, that Navistar (Powerstroke’s parent company) and Ford had a legal battle over it. The list of issues ranges from head gasket problems to catastrophic fuel system failures. And the best part is, most of these problems require remove of the cab for repair. Once a vehicle has been ravaged to the point of having its cab removed, do you really want it? Probably not. Buy a Ford with a 7.3L Powerstroke, instead.


Ford Super Duty 6.4L (2008-2010)

It didn’t take Ford long to realize the Powerstroke 6.0L works better as a boat anchor than a truck engine. So, the company scrambled to find a replacement for the ill-fated six-oh. The result was the Navistar-built 6.4L turbo engine – another pile of rubbish. While not as bad as the 6.0L, the 6.4L has a long list of problems. Highlights – or more appropriately, lowlights – include fuel system failure and oil dilution. The latter is a huge problem since it allows fuel to slip past the piston rings into the crankcase. This eventually results in lack of lubrication and catastrophic engine failure. After years of arguing over sub-par engines, Ford and Navistar parted ways like bitter divorcees in 2010. What a surprise.


These used diesel trucks are the worst of the worst. But there are also a lot of good used rigs out there. Notably, there are no Dodge trucks on the do-not-buy list. That’s because Dodge always sticks with stout Cummins-built engines. If you’re in the market for a used diesel truck, take your time and do your homework. Otherwise your dream truck may end up a broken-down yard ornament.





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