Disappointing to say the least. I am going back to 5W-20. Sheared back to a 20Wt. oil. Probably not Mobil 1. I wonder if 0W-40 would have sheared back as much.
Because is to better.What is your objective in running such a long OCI in miles and time? Why the oil much higher in viscosity than what Subaru specifies?
That car has stationary hydraulic lash adjusters and VVT. You don't want to go off the grid with viscosity. The HLA need a specific bleed down rate, the VVT phaser like a target viscosity to keep the cam in a good advanced angle for good torque at low and mid RPM. Important in a automatic.Well. I wanted to try 40 weight. Does that void my warranty...No. I wish to use longer intervals. Does that void my warranty?..No. I have a UOA that proves the oil didn't hurt anything. As I said. I am going with 0w-20 but I will extend the drain interval.
Long story short I do what I want within reason. I have the time to play games if they want to....they don't want to.
Those UOAs do not prove that your long OCIs are not hurting anything. They really can't tell you anything about deposits, especially without TBN, oxidation, and nitration tests. All they tell you is that engine wear is probably fairly normal.Well. I wanted to try 40 weight. Does that void my warranty...No. I wish to use longer intervals. Does that void my warranty?..No. I have a UOA that proves the oil didn't hurt anything. As I said. I am going with 0w-20 but I will extend the drain interval.
Long story short I do what I want within reason. I have the time to play games if they want to....they don't want to.
What’s the old saying? A penny wise and pound foolish?Those UOAs do not prove that your long OCIs are not hurting anything. They really can't tell you anything about deposits, especially without TBN, oxidation, and nitration tests. All they tell you is that engine wear is probably fairly normal.
If this is a daily driver, with 10k miles in 15 months, you're doing a decent amount of short tripping, including in cold weather. This will degrade the oil quickly, promote sludge, and is the reason the 6 month limit exists.
If you want to take chances with the warranty, that's up to you, but an extra oil change every year would cost you <$150 over the entire warranty period, would keep your engine in better shape, and would eliminate the need for UOAs. If you do stick with long OCIs, I'd at least get a TBN test.