how much can you overfill Subaru Impreza TS oil?

[bigpaulo]

I am fully aware of all the nasty things that can happen with *too* much oil, e.g. blown seals, PCV contamination, high oil consumption, frothing and general engine apocolypse

However, I've been somewhat convinced that having more oil is better (longer oil life, mostly, due to dilution of the polution

That said, I have no idea how much you can overfill a Subaru Impreza TS (non-turbo) before problems occur... since it is a boxer engine, the crankcase is on the same level as the piston centerlines, so you could really flood the engine with oil if you're not careful.

Anyone here have any specific Subaru experience on how much you can safely overfill? Or if I'm way off base with my piston/crankcase being on the same level?

Yes, I'm aware that you *could* just keep adding oil and checking for bubbles, but how reliable would that be anyway?

Thanks in advance for any advice!

 

[Patman]

quote:

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Originally posted by bigpaulo:



Yes, I'm aware that you *could* just keep adding oil and checking for bubbles, but how reliable would that be anyway?

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That's the most reliable way to find out actually.

 

[bigpaulo]

OK, well, I'm changing my oil this weekend, and I'm going to overfill it by 1/4 quart and see...

What's the best way to check for bubbles? Drain a little off the Fumoto valve? Or is it something you can see on the dipstick?

Actually, I should start with it spot on the full mark, so I can get a non-bubbly oil benchmark.

 

[Matt_S]

Actually, I don't know if I'd go the "add a little bit and see route". Once you start to see bubbles, the oil is already foaming and you're risking damage. I'd drop the pan, if possible, and manually turn the engine to see how far down the crankshaft comes, then measure how much fluid you can pour into the pan so as not to have it interfere, giving about 1/2" for safety.

 

[Patman]

quote:

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Originally posted by Matt_S:
Actually, I don't know if I'd go the "add a little bit and see route". Once you start to see bubbles, the oil is already foaming and you're risking damage.

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But if it's only a little bit over you won't be doing too much damage at all. It was MolaKule who originally told me that he does this method with all of his vehicles to determine max oil level, so I figure if he does it then it must be safe.

 

[tweeker43]

my 2.5rs will easily accept a fill of 4.5 quarts, even though the stated capacity is 4.2. you could probably get some info at www.rs25.com as well.

so hey, go nuts!

quote:

---

Originally posted by bigpaulo:
OK, well, I'm changing my oil this weekend, and I'm going to overfill it by 1/4 quart and see...

What's the best way to check for bubbles? Drain a little off the Fumoto valve? Or is it something you can see on the dipstick?

Actually, I should start with it spot on the full mark, so I can get a non-bubbly oil benchmark.

---

 

[Patman]

Just pull out the dipstick immediately after shutdown and check it, that should do the trick. Going 1/4 of a quart at a time is an excellent idea, you don't want to go too far all at once.

 

[Johnny]

I use 4.5 quarts also and would not want to go over that. As you say, everything lies flat.