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Oil and Oil Filter Questions


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Hi all,

 

I have a 1998 LGT, AT, 215K miles. Recently, a co-worker suggested that I try using a diesel intended engine oil. Specifically the Shell Rotella (550019921) T6 5W-40 Full Synthetic, Heavy Duty Diesel Engine Oil (CJ-4). In addition, he said that I would need a larger oil filter with this type of oil.

 

So, my question is, has anyone been doing this with their older engines and would the Subaru 15208AA15A Oil Filter be okay to use instead of the 15208AA12A Oil Filter?

 

Thanks!

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Your car is rated for 10W30. A full synthetic will generally leak some ( for how long IDK) past your seals as it is more viscous.

Larger filter? Never heard of it.

Other than change intervals what benefits do you expect?

 

O.

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There is a bit of a bandwagon around Rotella (brotella). It seems like whatever oil you have been using is working pretty well for you. Any of the good quality "high-mileage" oils of the correct weight and spec would probably help quiet the noise. The OEM Subaru oil filter is designed with the correct bypass valve pressure and is a good choice.
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Your engine was built to run a 30 at operating temp. If you change that (especially on a car that has run the same oil for 200k) you risk having too much oil pressure. It makes a huge difference. You could argue that engine wear would allow you to run a thicker oil with no problems, but really if it aint broke dont fix it. If you do run a thicker oil run 5w40 or 10w40 depending on what you were running before ESPECIALLY if you are in a cold climate.

As for synthetic oils making your car leak, thats not how it works. Synthetic oil doesnt change viscosity that much when it breaks down as opposed to conventional oils which thicken up quite a bit toward the end of its life. Synthetic tends to wash out deposits of old broken down conventional oils and helps you find existing leaks. The same thing would happen if you ran a cleaning detergent additive in your oil. Synthetic doesnt clean your engine any more than conventional would, it just doesnt break down nearly as fast. Hence the longer oil change intervals.

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