I have a turbo diesel which the manufacturer recommends a 5W40 full synthetic so I run Shell Rotella T, 5W40 .  I was on a long trip in the mountains and noticed I was a bit down but no one had it so I added Chevron Delo 15W40.  Well, it made it home fine but should I change the oil?

I am 4000 miles from the next scheduled oil change.

15w40 would seem a little heavy...but you should be fine.  I don't see why it wouldnt blend in with the rest.  If money isnt an issue, and you're worried about it, then change it.  

It's not a problem to mix full synthetic oil with regular oil. Some companies offer synthetic blends that are mixed. Just continue using your normal oil change schedule, no need to change it now.

Everything seems fine after putting 500 miles on it.  I'd like to "use it up" before cool weather sets in but in the meantime, I will be gentle on the throttle until it is warmed up.  The little turbo really likes to spool up, something on the order of 120,000 RPM and it has regular hydrodynamic bearings.  Water cooled but no ball bearings.

Another interesting thing was the aftermarket plastic boost gauge hose ruptured from the heat.  I bet the lost oil is now pooled in the intercooler, reducing its capacity to cool the intake and allowing hot air to rupture the hose.  It sure was ballooned out...fortunately I had a second ferrule and plenty of tube to make the repair.

Most quality motor synthetics can be mixed without any problems. Mobil 1 and Amsoil say they are fine in a pinch to be mixed.

You might want to check your specific oil type.  

Your engine will implode, causing a black hole that will immediately suck you, your truck, the road, and ultimately the universe into a singularity.  Thanks.  



It will be fine.  The Atoms and Molecules from the Full Synthetic Shell and the Chevron oil are now happily co-lubricating your engine.  

Quoted: Everything seems fine after putting 500 miles on it.  I'd like to "use it up" before cool weather sets in but in the meantime, I will be gentle on the throttle until it is warmed up.  The little turbo really likes to spool up, something on the order of 120,000 RPM and it has regular hydrodynamic bearings.  Water cooled but no ball bearings. Another interesting thing was the aftermarket plastic boost gauge hose ruptured from the heat.  I bet the lost oil is now pooled in the intercooler, reducing its capacity to cool the intake and allowing hot air to rupture the hose.  It sure was ballooned out...fortunately I had a second ferrule and plenty of tube to make the repair.

Very interesting, we don't really see diesels around here at our shop.
What kind of car do you have?