Been running Mobile 1 Synthetic since 15K.(Now @ 68K) Can I switch back to regular oil without problems? Volvo dealer says NO, it will ruin the engine? Something about the size of the "burrs" in the metal will rise up again??

LOL
Thanks for my first chuckle of the day. It is all in the weight of the oil and frequency of the oil filter change. The problem is trying to get 5W oils that are not synthetic. Turbos create a lot of heat so they need a "thicker" oil which will not break down, and that is why I use synthetic 5W40 in my turbos.
BTW, I would only have a turbo equiped car in high altitude. Even the low pressure turbo in the GLT will supply enough air to keep the horsepower constant at above 5,000 feet.
You folks in CO don't get the wet, mushy snow that sticks to the headlights, so headlight wipers are probably not needed. Dried bugs will not come off with an occasional wipe, use the squeege at gas stations for that.

Klaus
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(V♂LV♂s 1995 854T, 1998 V70R)

Who is this Joker? I have owned more Volvos than most people have owned cars and have used synthetic, dino oil, and switched between on a few cars with ZERO issues. This is complete BS from the dealer. AS long as it is the proper grade oil and rating you are fine.

I have a 95 Turbo that I bought used that I have beat on hard and I use NO BRAND oil from a local autoparts store. Yes, no brand but it has the API logo and so far, 80K miles it is fine. Now has about 170 K on it.

If you want to switch....switch!

I think I smell the aroma of doo doo in this advice.

Nonsense - if Volvo could somehow rein in their dealers and service people (or if they really cared to do so) they might could sell lots more cars. Use the weight and service grade the manual or Volvo website says - doesn't matter if conventional or synthetic or blend, change it and filter at appropriate intervals, especially if car is in severe use - and keep your cooling and fuel systems in good shape so oil will not get overhot or prematurely contaminated - that's all there is to it.