For my 2016 Outback 3.6R Subaru recommends its own synthetic oil and a 3,000 mile change interval.   That seems ridiculous for our moderate Ohio climate.  I have a 1997 BMW that has done very well on Mobil 1 changed at 7500 mile intervals, and I have confirmed this by Blackstone oil analysis.  

 

I'm asking this forum whether there is reason to think that Subaru Synthetic Oil has any advantage over Mobil 1 and also whether a 3,000 mile change interval is a benefit to my engine or just to the Subaru dealer?   I'd like to use Mobil 1 and a change interval of 7500 miles. 

Why aren't you following your owners manual?  Back up, and start there. 

 

You're over thinking this - "Subaru" does not recommend what you're saying, the problem here is that you're giving credence to inappropriate sources.

A mechanic, shop, or "service advisor" is generally not even close to the best source for best maintenance approaches.  They're bound by one-size-fits all organizational constraints and not vehicle/owner specific goals. 

You can always beat mechanic/shop maintenance practices if you have a small amount of time and capacity to learn.

 

But even if you don't have any of that - Follow the owners manual, Subaru doesn't make oil so you are correct that their oil offers nothing over other options that meet the owners manual specifications.

"recommended" does not mean "required".

"recommended" from a salesmen is definitely largely unimportant without some compelling data behind it - which obviously isn't the case here.

 

http://www.cars101.com/subaru/outback/outback2016.html#maintenance

 

Clearly stated 6,000 miles and synthetic oil, like these dealers publically state (though their other intervals and suggestions should all likewise be ignored):

http://www.planetsubaru.com/subaru-service-and-maintenance-menu.htm

http://www.patriotsubaru.com/subaru-service-schedule---2015-models.htm

http://www.stanleysubaru.com/new-subaru-maintenance-intervals.htm

 

Of course a dealer recommends things - do you always follow to the "T" every single product recommendation you buy in the owners manual, on the receipt, on the website, on their tag, on their label, on their documenation....no of course not, you don't even look at or know all that stuff for every gadget, device, appliance, supply, and product in your home. 

Pretty much any car 2010 and up I run full synthetic for 7500.

 

I run Amsoil signature 0-20 I'm my sisters Hyundai for 20k. Tested every other change by OAI. I could run it longer by mileage, but typically change it at one year.

A 3k change with synthetic is ridiculous with modern engines and oil. Plus Subarus don't tend to be very hard on oil unless turbo charged. So I think you have pretty good advice on 6-7.5k changes. I would go 7.5k myself!

I go 15k on Mobil 1. I live in the deep South where it's 100 deg. in Summer. I have never had a problem with an engine (car or motorcycle) doing this. Mobil made the claim many years ago that synthetic oil would hold up that long. My brother, a mechanic, ran his van over 200k without changing oil ever. He only changed the filter and topped it up every 25k just to see what would happen. He sold it to a friend and it's still going with over 300k. Unless you drive in a high dust/dirt environment you aren't going to "wear out" your synthetic oil that quickly. That 3000 mile oil change was for old style oil when we used leaded gas.