Canuck,
I sent the dealer an email wondering why it was omitted after I had it in the shop -- looks like they just forgot. She couldn't really give me a straight up answer as they have literally hundreds of them on the parts shelf.
Canuck,
Even on Honda cars, the dealer ALWAYS uses a new oil drain plug washer. The reason is because the new washer is a "crush" washer, and when you tighten the drain plug, the washer "gives" a bit as the drain plug is tightened, thus creating a torque seal preventing the drain plug from backing out. Without the washer (or using an old previously crushed washer) will not afford you the torque crushing for one thing and secondly, you'll have to tighten the plug a little more to get to the point where the plug won't back out. Here's the bad part (in theory); because there is no new washer to "crush" and take up the load, the load is transferred instead to the threads on the crankcase. As with the cars, I've seen many stripped oil pan threads from people using the old washers. Save yourself the possible headache of stripped crankcase threads and buy a bunch of the aluminum washers to replace every time you do an oil change. I have literally dozens of them for my family's "fleet" of 4 Honda Fits and I have NEVER had a problem of stripped threads, even with over 100,000 miles on one of them. The Honda dealer wouldn't require a new drain plug washer on every oil change if there wasn't a good reason (I seriously doubt that they're so "hard up" on making money that the "expensive" 40 cent washer would make or break their profit margin.)
