Just wondering if it would be counterproductive to drive our new 2014 Impreza on a long trip 600 miles- (300 miles each way- mostly 70 MPH driving on I-95) with the original oil still in the crankcase. The car currently has 1,900 miles on the clock (so it's well over the 1,000 recommended break in period).

 

I was planning on changing the oil at 2,500 or 3,000 miles for the first change and 4,000 miles thereafter (since I am running synthetic- I've always changed conventional oil at no more than 3,000 miles and less if it's a vehicle that's not driven daily). The car should have just over 2,500 miles when my wife returns with it. I'm just concerned that that amount of high speed driving with the original oil could cause more harm than good, so I'm thinking about having her take our van instead (which will suck up 2X the amount of gas, unfortunately).

 

I ordered some Subaru oil filters which will be here next week, so I'll likely change the oil soon regardless. 

Recommend changing the oil. It is the right thing to do for the car.

Any more there is no real break in period for your oil.  There is a break in period for the gears in the transmission, front and rear ends.  You don't want to drive at a constant speed and want to vary it up and down for the first 1000 or so miles so you are over that. 

 

Changing the oil is up to you, you can either change it now or later it really doesn't matter.  You might also want to look into a oil analysis just to see when you really need to change the oil and since you are running synthetic odds are you can go way past 5,000 miles.  I use Blackstone Labs for my diesel and Subaru for the oil analysis. 

In the case with most late model vehicles, it is generally recommended to leave the factory fill oil until the oil change reminder lights come on. Personally, i would give it 5000 mi before changing it.

 

Otherwise, if you change it for the sake of a road trip. you should consider 0w40. Do this if you find that the engine consumes a quart between oil changes with 0w20 or 0w30. Good luck

Basically it doesn't matter, its up to you.

Personally I go for a motoman style break-in and change at oil/filter @ 500/1000/3000 for new motors. But it's definitely overkill and probably not even required.