Engine ran without oil after service

Others will weigh in with their opinions, but in my view, you're working with a pretty trustworthy dealer, assuming they approached you with their mistake. The damage you listed sounds minimal. While not the ideal solution, I have seen people just slap in new sets of bearings into higher-mileage engines, then never have a problem after that. The fact your dealer wants to involve a professional engine machine shop suggests they're going above and beyond to protect your best interests. I would thank them and let them take care of everything. At the dealership I used to work for, we also had happy car owners bring us cookies or donuts about once a week.

We used to have "endurance" races where the oil and coolant was drained, then the cars were raced to see which one could make it farthest or last the longest. Many went for over 10 miles and were still running when they finally gave up and halted the event. They were raced gingerly to reduce stress, unlike regular racing that is all-out and high stress, but the point was many engines are really tough and can hold up to abuse.

Oil to the cylinder heads is much less critical than to the bearings. Camshaft lobes, rocker arms, and push rods can hold a film of oil for a long time and will need a longer time before they start to develop wear. When they found the wear to the crankshaft, (main), and connecting rod bearings, there is also the chance corresponding wear has taken place on the crankshaft journals that ride on those bearings. The engine machinist will check for that wear and measure the journal diameters to see if they are still in specs and the crankshaft can be reused.

Another factor is piston scuffing. That can't be seen until the engine is disassembled. Pressurized oil squirts onto the cylinder walls to lubricate the piston skirts. Being made of aluminum, pistons without a film of oil will start to tear apart, or "scuff". It takes longer for the steel cylinders to develop wear, so chances are the engine block is still fine. That scuffing can lead to flakes of aluminum dropping into the oil pan. If they make it into the oil pump and past it, the filter will catch them. The specialist will look further if he sees any signs of metal chips have circulated beyond the filter. Those chips can lead to other or repeat problems if they aren't caught right away.

As for reliability, that doesn't even enter the equation. You had an engine that was assembled on an assembly line with minimal human interaction. As such, chances are you'll get a high-quality engine, but there's dozens of things that have an acceptable range of measurements that must be adhered to. To say that a different way, not many engines will end up being perfect as compared to design specifications. Now you're going to have a one-of-a-kind, hand-assembled engine where the specialist checks and rechecks every measurement. The chance of making a mistake is more likely compared to the assembly line, and the chance for building a better engine is also much greater. It depends on how careful the people are who are doing the work. This is what they specialize in.

Also, almost every manufacturer comes up with quality, reliability, and customer satisfaction notifications they provide to the industry. None of those updates or improvements may be necessary, but they usually are incorporated when they can just be included as part of the job. The aftermarket industry also often comes up with small improvements that others copy when appropriate.

You can be sure a mechanic got reprimanded at a minimum, and possibly even fired for this mistake. My recommendation is to be patient and wait for the call that your car is done. They likely gave you a loaner car, and they're already embarrassed by their mistake. They're really going to appreciate one customer who is not angry. I don't see this as having any impact on resale value. Any engine can need gaskets and seals, a new water pump, a timing chain or belt, but we only look at those services in a positive light as the vehicle was properly maintained. Your engine's repairs are a little more involved, but not to the point of lowering its value.

I don't see your model listed in my online service information, but I did find a 2.1L diesel engine in a model E250. I only posted this drawing to give you some reference as to what will be done with your engine. Item # 33, (red arrow), is one of the pairs of crankshaft bearings. Each pair is clamped around a crankshaft journal, (pink arrow), and the "clearance", or space between them is measured in thousandths of an inch. That's the space where pressurized oil is forced in to prevent metal-to-metal contact. Those bearings are made of three layers of metal. The first layer is very soft so particles of dirt or metal will embed in them rather than gouge and damage the highly-polished surfaces. It's that layer your dealer found to be worn away. The next layer is a darker color so it's easy to identify.

Similarly, item # 32, (green arrow), shows half of one of the four connecting rod bearings. There is also a tight clearance between those bearings and the journals they ride on. The blue arrow is pointing to one of those journals.

Item # 29 shows one piston assembly. The orange arrow is pointing to the skirt. That rides on the cylinder wall and holds the piston straight. Most often these pistons are "cam ground", meaning they're slightly oval in shape. When the engine reaches normal operating temperature, they expand nonlinearly to turn into a nice round piston that fits just right with the proper amount of clearance. Being slightly too small when they're cold, they can rock or slap causing a very slight noise that goes away after warmup. That's considered normal and is more noticeable on some models; less on others. You'll never hear that little noise over the normal rattling sound diesel engines produce.

I hope that helps to put this in perspective. This mistake happens quite often at the speedy-lube places, often because multiple inexperienced people work on one car. Too often each assumes the other put the oil in. This happens more often when the boss pushes his people to work faster and faster. Conscientious employers emphasize doing it right over speed.

Let me know if there's anything I can clarify or explain.

I think this will have a good outcome. We had a lot of understanding customers and were appreciative for them. Please let us know how this turns out.