Car - 2005 Mustang V6 with about 75K miles
Oil - Pennzoil Platinum 5w-30
Miles on oil - 6,100
Driving habits - mostly short (less than 15 minute) trips...but lots of them with the occasional 300 mile weekend excursion mixed in
Issue - checked the oil the other day and the dipstick indicated an okay oil level (maybe down half a quart). It seemed really thin though, almost watery. I did about 5 dip-and-wipes as I was surprised by this. Outside temp was about 50, engine was cold. I knew that at 6K the oil was due anyways so I changed the oil right then and there and it was extremely thin and watery as it drained, unlike anything I've ever seen throughout about 50 oil changes. I replaced it with 10w-30 QSUD that I had on hand. I am really concerned about how thin the oil was. No, I did not do a UOA, I was not in a position to do one at the time, it was more of a spur of the moment oil change and the oil that came out went into the oil drain that I've used for 10 years and 50+ oil changes plus other fluid drains so it has all sorts of contaminants in it.
Other info - about 4-5 months ago the water pump went out and it was driven for about 20 miles with water in the radiator. After the water pump was replaced I did an oil change. Everything else about the car seems A-OK.
Any idea why the oil was so thin and watery? I've used Pennzoil Platinum in other vehicles before and never seen this behavior. I'm not an oil brand loyalist and have used just about every one of the big boys..
oil extremely watery at last change
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What weight oil does it call for? I have a hard time believing PP is to blame. Its one of the best out there. When you say thin and watery, do you mean it might have had water in it? Or that it had just thinned out more than you expected.
You probably had 5W-20 in there thinking it was 5W-30. That 5W-20 is a very close cousin to water.
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Probably means thin. Kind of hard to tell by watching it pour out of the pan.
Originally Posted By: Merkava_4
You probably had 5W-20 in there thinking it was 5W-30. That 5W-20 is a very close cousin to water.
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No, it was 5w-30 Pennzoil Platinum. Manual calls for 5w-30.
To compare, my Suburban uses 5w-30 and it has never come out that thin. Here's my unofficial, non-scientific test...I loosen the drain plug with a ratchet and then remove by hand. When the plug comes out oil always gets all over my hand. Typically it slowly runs down my hand and I almost always have time to get a rag before it gets to my wrist...
This time it was almost to my elbow. It was a water-like as a I have ever seen oil, especially with a cold engine.
I'm thinking, run the new oil for 1,000 miles, then do a UOA???
Originally Posted By: Merkava_4
You probably had 5W-20 in there thinking it was 5W-30. That 5W-20 is a very close cousin to water.
Originally Posted By: TNBurban
Car - 2005 Mustang V6 with about 75K miles
Oil - Pennzoil Platinum 5w-30
Miles on oil - 6,100
Driving habits - mostly short (less than 15 minute) trips...but lots of them with the occasional 300 mile weekend excursion mixed in
Issue - checked the oil the other day and the dipstick indicated an okay oil level (maybe down half a quart). It seemed really thin though, almost watery. I did about 5 dip-and-wipes as I was surprised by this. Outside temp was about 50, engine was cold. I knew that at 6K the oil was due anyways so I changed the oil right then and there and it was extremely thin and watery as it drained, unlike anything I've ever seen throughout about 50 oil changes. I replaced it with 10w-30 QSUD that I had on hand. I am really concerned about how thin the oil was. No, I did not do a UOA, I was not in a position to do one at the time, it was more of a spur of the moment oil change and the oil that came out went into the oil drain that I've used for 10 years and 50+ oil changes plus other fluid drains so it has all sorts of contaminants in it.
Other info - about 4-5 months ago the water pump went out and it was driven for about 20 miles with water in the radiator. After the water pump was replaced I did an oil change. Everything else about the car seems A-OK.
Any idea why the oil was so thin and watery? I've used Pennzoil Platinum in other vehicles before and never seen this behavior. I'm not an oil brand loyalist and have used just about every one of the big boys..
With the results as described this might be breakdown due to shearing. It seems unlikely, but it could be production defect. It could be extreme heat, but you said you did an oil change after the waterpump issue. The waterpump failure could have resulted in high peak tempatures that caused mechanical changes in the tolerances of the engine.
It is counter-intuitive, but resist the urge to increase the weight of the oil. Cut your interval down to 3K and monitor the oil closely at least evey 1K.
I had a situation like this a few months back in my truck, with PU comming out, I wouldnt say mine was "watery" but it seemed much thinner comming out than going in (and yes the engine was cold as well ) I drain into a yellow pan then pour into the bottle my fresh oil just came out of. When i did this i got to scratching my head as the oil truly did seem "thin". I went and got a fresh bottle of PU of the shelf as i wasnt using PU on the OCI that just went in. For comparison purposes i cracked the lid and poured a little out (i know this is'nt scientific) into a clean container to see how it poured compared to the oil fresh out of the block.. the Old oil was deffinately pouring much faster.. some of you in the know can probably explain this. Ive never noticed used oil to be that much thinner comming out than going in.. but thats just me.
it had just under 5,000 on this OCI with PU 5-30 in it. 64,000 on the clock. and the OLM was indicating just over 20%
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Did you sniff for gasoline?
as a matter of fact i did, and detected nothing. this OCI was 2,500 or so normal DD, the second half was vacation 99% highway/interstate. the colour of the oil was ok, noticed no gas fumes, water dropplets, or any other kind of contamination. Oil filter looked like it could have gone another 5,000. (of course without a UOA i cant know for sure) ive got 2,600 on this current OCI and have monitored it pretty close with Valve Syn in it.. its nothing like what came out of the last OCI.. i will be able to do a better comparison when this ones done. all other fluid levels are perfect as usual.. truck runs flawless..
I've noticed this with almost every oil change I've ever done on my car, whether it's Mobil 1 EP 5w30, Castrol Syntec 0w30, Rotella T6 5w40 or Rotella T 15w40. Much thinner coming out than going in. This is a good thing, IMO, as long as you aren't seeing excessive oil consumption or fuel dilution.
I've also noticed this with both of our Subarus, both NAs.
This is partly the result of the unusually large drain plug Subarus have, which results in the oil draining more quickly than it does with most cars.
Still, the oil does seem thinner coming out of the Subies than it does with any other car I can recall.
A couple of questions:
Are Subarus known to shear oil to an unusual degree?
Do Subarus have unusually high bulk oil temperatures?
Since this seems to be a Subaru thing, and is maybe the source of that bit of Subaru lore that Subies like thicker oil, I'm not too concerned.
The flat fours still seem to live long lives.
Was the engine making any noises?
I've noticed this several times in my lifetime(1,000's of OCI's)but, usually when the oil was extremely ))HOT(( regardless of the wgt of the oil
Although, I have poured "NEW" 5W20 or 0W20 virgin oil from the platic bottle and it too was quite thin when cold. All that I can add to this topic is to keep an eye on the next OCI to see if things change.
As long as the engine didn't complain during the last OCI, I beleive you'll be fine unless you noticed a milky texture to the oil. Also, the smell of fuel in the oil can be deceiving too because it only tells ya that the oil has a fuel smell, not how much!
A UOA is the only way to really judge this situation but too, this thin oil kinda shows ya how thin an oil can be and still protect 
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Actually if you were to drain your oil when it was at operating temperature (which most of us never do) it would appear to be very watery. At 100C, (212F) platinum is 10.3 cst, which to the human feel is very thin. Water at room temperature (22C / 71F) has a cst rating of 1. Ethylene glycol @ 70F has a viscosity of 17.8, so think about how undiluted coolant feels, motor oil is even thinner when heated to near operating temperature. Most of us drive our cars or trucks to warm them up before we change the oil, when in reality we never get the actual oil anywhere near 212F. Did you drain the oil after a long trip? (More than 10 miles)
SAE 30 motor oils have a viscosity range of 9.6-12.9 @ 100C / 212F.
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This is where a UOA would actually be valuable (as opposed to how many on here like to use their data....) to see the viscosity and see if it sheared down or not... If the flash point was lowered.....etc.
Sounds like gasoline contamination .
Probably just sheared down.
I drained surprisingly watery oil out of my inboard ski boat. It was 10W-30 MC 5000. I put Delvac 1300 15W40 in and the engine was noticeably quieter. I should have used HDEOs sooner in it.
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