Do Motor Oil's have there own unique Smell ?

I recently had my oil serviced about 3500 miles ago. I have always used Chevron Delo 15-40. But recently since the service, I have noticed a different smell coming from the blow by. I checked for water in the oil, and oil in the water and all is clean, as a matter of fact the oil is still golden yellow. But the oil on the dipstick even smells like the odor from the blow by.
Im thinking maybe they put a different oil in it, I tried to compare the viscosity by rubbing my fingers thru the oil and fresh oil from a Delo jug. The one on the dipstick was slicker, BTW I dont run Lucas anymore.
I had a shop mechanic check it out and he said it smells like "synthetic". Now I use synthetic in my 4 wheelers and I did notice a resemblance on viscosity and slight on the odor. So did I get away of paying for regular delo in exchange for synthetic ?
I have used Shell Rotella way back and didnt like it and it didnt have the smell Im speaking of, I have never use Delvac either, So can a few member's here enlighten me to what might have happen.

 

I have had Rotella before and it didn't smell like it does now.

 

Taste test !!!............ Hell, why not, it might do me good internally.........lol.... Seriously though, just might do that and go to the shop. I've been there a few times and never had a problem. For $220.00 I get oil change(choice of oil), lube and CAT filters. It's cheaper than me doing it myself.

 

By the time I buy the oil, CAT fliters(1 oil, 2 fuel, 1 water) and grease, Im close to $200.00. For another $20.00, the oil/lube shop could do it. Isn't that common sense ?