Luck vs talent

Following your economics and risk management theory it makes perfect sense; have you not seen all the dealer oil change debacles? Over tightening and stripping and snapping skid plate bolts, over tightening and cracking oil filter housing, over tightening and stripping oil plugs, not replacing the oil fill cap, on and on.
If you have a competent person doing oil changes, transmission fluid exchanges, diff fluid, you run very little risk of making things worse than they were if you hadn’t serviced them at all.

 

Only way I would let my dealer change my oil is if I welded in a 18-20 mm bung with threads so thick you'd need to intentionally thread it incorrectly to get it wrong. Also the bolts would be on a dangling chain so they can't lose it.

There would still be that one technician though who'd used an impact wrench to put it back under 10-20 ugga-duggas, so it's not foolproof.

 

Gotta make em work for it.

 

That's why I change my own oil. But that's still not an apples to apples comparison. The Toyota mechs are not recommending never to change the oil (engine, tranny, diff, etc.), they are specifically saying to leave the diff or tranny oil (whichever was the subject of their guidance) alone if it had not been changed per the maintenance schedule for some undefined long period of time. Your argument ignores that criteria, at least, and possibly other criteria as well.

 

I've never heard that for the differential fluid, only the transmission which I understand why.

 

Yeah I’m not sure why this is shocking to people. It’s more dangerous to open a tranny that’s been sealed for 200k than to let it ride with original fluid. Makes sense to me.

 

I have questions.

 

I dont have any answers. I was looking for a pic of a welded on drain plug, but found that.