By the late 90's Frito-Lay was buying strictly 6.5 diesel steppers. By the time Workhorse came along, they maintained the fleet as only 6.5's. They had a deal to buy new engines from GEP and reman transmissions from GM. When the chassis hit 250k-ish they got sent back to HQ in Texas to be refurbished with the new drivetrains. They went through from bumper to bumper.
Though by the time Workhorse was selling them, GM Powertrain had thinned 6.5 offerings down to one that the injection pump was set for sea level elevation. So high elevation applications tended to be a bit fat on fuel due to the lack of air. Which, ordinarily wouldn't be an issue for anybody but Frito. Which is where I came in following the letter of our warranty.
A quick backstory. While GM was still making the P30 some crackpot engineer gave Frito a document approving them to bump the oil change interval to 5000 miles. Again, normally that wasn't an issue but Frito couldn't follow that. Frito made it corporate wide to move to the 5000 mile interval even as Workhorse took over production.
So fast forward to when I get a call from my dealer in Sante Fe NM. Frito truck with a failed 6.5. Pulled the pan and had nothing but pudding in it. Though if you pulled the stick, it would look like it was full of liquid oil. This stuff would be a gelatinous goo that the oil pump couldn't pull through and caused the main and rod bearings to starve and fail. My dealer was pretty certain it was lack of maintenance, but being our biggest fleet customer at the time I approved the engine replacement. But my dealer wrote the date and mileage on the new oil filter just in case. Sure enough, less than a year later the same truck got towed in with the same problem. It had 10,000 miles on it and the same oil filter was on the engine. The extended oil change interval didn't help, but that wasn't the main cause of the pudding. We came to the conclusion the low altitude injection pumps combined with NEVER shutting off the engine when making delivery stops with the extended oil change interval was the issue. Idling for hours while they unloaded and already over-fueling from the low altitude IP's just washed down the cylinders with diesel fuel. The resulting mixture congealed and wouldn't get pumped.
That case prompted a dog and pony show between Frito, Workhorse, and GM Powertrain at the old GM parts plant in Denver. Since it was at my dealer I got hauled into the mess with Larry and our Bosses from Detroit. Full-on blame game finger-pointing and Frito holding this old Memo from GM saying they had the ok to go to 5k. They were hanging on it like it was the get-out-of-jail-free card from Monopoly. Had they actually changed the oil at 5k they would have limited the amount of fuel in the oil to cause the fuel/oil mix even if they still run them at idle at all the stops. We finally reached the consensus that they would actually change the oil at 5k and limit the idle time so the engines would not fail. GM wasn't going to change and bring back the high-altitude IP so they had to adjust or start paying for a lot of engines.
So much fun in the world of corporate ass-kissing to maintain the fleet so we could sell another round of units.
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