I am now getting ready to buy another new vehicle, and my question is this: Am I wasting my money having the dealer change all these fluids so soon, or is this still a good idea for the drivetrain?
A Wonderful question! Like you, I tend to be somewhat obsessive in maintaining my vehicles (my boys tend to use a more graphic term for it). The core of my motivation is, of course, money. I want to squeeze absolutely as many miles from my vehicles as I can at the lowest possible cost per mile. That means keeping the vehicle -- whether purchased new or used -- for its entire service life until it is fully depreciated and has reached "beater" or salvage value.
The only new vehicle we ever purchased was our 1996 Chevy Tahoe, which we still have and drive. It now has about 140,000 miles on it and is still a very nice truck -- particularly after I replaced the A/C compressor this summer.
When it was new, I changed engine oil and filter to full synthetic at 1,000 miles and changed the automatic transmission fluid from petroleum to synthetic at 5,000 miles. I changed both differentials to synthetic fluid at the same time.
Did it pay off? Depends on your definition of "pay off." From a comfort-zone perspective, I thought I had done all I could to maximize the life of the drivetrain. Because I did the services myself, my only costs were the synthetic lubricants and filters.
The results? Somewhat surprising. At about 53,000 miles an intake manifold internal coolant leak caused main and rod bearing damage that was covered under the extended warranty we had purchased. The engine has been perfect ever since.
At 83,000 miles, when I went to change the transmission fluid for the third time, I discovered significant amounts of metallic and clutch debris in the pan and filter. The transmission was near the point of failing and required a complete rebuild. My bad -- I had waited a bit too long and the warranty had expired. Lesson learned.
At 125,000 miles, when I was again changing transmission and differential lubricants, I was stunned to find huge chunks of the rear diff's spider gears stuck on the magnet on the unit's cover. Once again, it appeared I had caught a major problem just before a complete failure. I ended up installing a used non-limited slip differential carrier and spider gear assembly, and the truck has been fine ever since. Two teenage boys driving this truck may have been a factor -- need I say more?
Now, contrast this with the used trucks my oldest son buys and drives. The first was a '92 K-5 Blazer that he sold with nearly 250,000 miles on it. He now has an '03 Silverado with more than 230,000 miles on it. And he does absolutely minimal maintenance on his vehicles. Who said life is fair?
Was my obsessive maintenance worthwhile? I think so, for two reasons. I felt like I did everything I could to maximize vehicle life and, perhaps more importantly, I caught both major problems before complete failures that would have stranded the vehicle. That meant I could repair them on my timeline and my terms.
Your new vehicle will be your responsibility. I don't see any downside in changing fluids early to remove any break-in debris. It may not be necessary, but it can't hurt.