2.5 NA Used Oil Analysis

[Bimmer]

Hi guys,

I had this done back in September, but I'm only getting around to posting it now.

This is from my old Impreza, but it's the same 2.5NA engine as in the Outback, so I thought it might be of interest.

I don't drive this car much... it had been over two years since I'd changed the oil, but I'd barely put 6,000 miles on it.
I changed it at that point instead of waiting for the regular 7,500 OCI because I was going overseas again for several months, and I didn't want to leave the oil in there any longer.


I'm glad I changed it when I did...

The TBN number makes me think that the oil was basically shot (despite Blackstone saying to run it another 1,000 miles).

I'm also mildly concerned about the "trace" of fuel — I took took several long, fast drives before changing the oil, which I would have thought would have burned off any fuel contamination.

And something's fishy with the flashpoint and viscosity well down in the 30w range.


Next time I'll only let it go 5,000 miles (that'll probably be early 2014, at the rate I'm going).

BTW, I was going to re-oil my K&N air filter (it's been in there 40,000 miles or so), but seeing these low silicon numbers, I won't even bother.

[the evil twin]

Interesting on the trace of fuel, I wonder if molecular bonding prevented it from being completely burned off since it sat so long. In regards to the TBN, additives break down over time which is part of the reason time intervals are recommended if mileage is not reached.
I just got my analysis back yesterday. Guess I'll post it as well!
FWIW, I remember reading somewhere (Mobil/ Valvoline?) thet the shelf life of an opened container of oil (unused) should not exceed 24 months.

[Bimmer]

Originally Posted by the evil twin

Interesting on the trace of fuel, I wonder if molecular bonding prevented it from being completely burned off since it sat so long.

Really? I didn't even know that this was possible...

Originally Posted by the evil twin

In regards to the TBN, additives break down over time which is part of the reason time intervals are recommended if mileage is not reached...

FWIW, I remember reading somewhere (Mobil/ Valvoline?) thet the shelf life of an opened container of oil (unused) should not exceed 24 months.

I guess this makes sense — oil oxidizes if exposed to air — and I'm not doubting you, but can you point me to where you saw this?

[the evil twin]

Originally Posted by Bimmer

Really? I didn't even know that this was possible...

May have been a poor choice of words. My real meaning was this: Depending on what they are looking for/ at in the analysis, traces of fuel may still be found even if the fuel is gone. For example, on average gasoline has 8 carbon atoms per molecule and motor oil between 18-34. Perhaps if the analysis shows an abundance of C8 the assumption is that there is fuel. Alternatively, the same could be said for 2,2,4-trimethylpentane (octane) which is derived from the distillation of oil. If there is any trace present (after it has broken down over time) perhaps it becomes harder to burn off as the molecules bond/ disperse.
It is all truly conjecture, I'm a mechanical/ energy engineer. It has been a long time since chemistry on that level. What I do know is that any substance man forces into a particular molecular structure does not want to stay there. Forces of nature and all. That said, I would really like to know.

Originally Posted by Bimmer

I guess this makes sense — oil oxidizes if exposed to air — and I'm not doubting you, but can you point me to where you saw this?

On the Mobil site they say 5 years "tightly sealed, cool and dry". I don't think a sitting motor would be considered cool and dry
Shelf Life on Opened Bottles of Mobil 1
Also, my supplier for the race bikes oil (Motul) said max 2 years in a garage. I had asked about getting 5 or 10 gallon drums since I go through so much and he said fine as long as I go through it in a year or two.
So I just put 2+2 together. Although, he does want to sell me oil at +$10/qt

[Bimmer]

OK, this makes sense.

There was just a lengthy discussion over at the Miata forum (when they weren't busy trying to figure out which antenae to buy).
A lot of the Miatas are 3rd or 4th cars, and a lot are parked all winter, so they don't rack up a lot of miles...

The opinions seemed to be either (1) just change it to be on the safe side, or (2) what could go wrong with oil just sitting in the crankcase?

FWIW, I think the Motul guy was yanking your chain... I can buy processed foods that are good for more than two years!

[the evil twin]

Originally Posted by Bimmer

... I can buy processed foods that are good for more than two years!

I think I'll start eating motor oil
Motul's standards are probably very conservative, as are most suppliers. I assume it is the addatives and detergents that fall out, not the oil itself that "goes bad". Either way I will follow his advice for a motor that spends it's life at 14,000 rpm!
Hmmm, now I want to find someone with access to a centrifuge and run some new oil through it!

[grossgary]

Originally Posted by Bimmer

(2) what could go wrong with oil just sitting in the crankcase?

maybe new oil sitting would be better than having 4,000 mile old oil sit in it for a year? i think about it in my truck because i don't drive that huge honking thing much, so i try to have it sit with clean oil. analysis would be interesting on that thing like many here are talking about with cars that sit or have low miles.

oil use/analysis gains are for proper intervals and saving time/money.

Subaru owners are not reaching the mechanical limits of bearing surfaces and piston rings in the short blocks of their vehicles, as anyone that's been tearing apart Subaru blocks since the 80's will tell you - with 300,000 miles an average maintained Subaru engine has the original cross hatching in the cylinder walls every time and good bearings.

there are a litany of issues that creep up before oil supply related stuff - valve adjustments, head gaskets, seals, gaskets, timing chain tensioners, timing chain guides, engine sensors, i can make a huge list of "common" (relative to oil related issues and very high miles), issues - many of which i've seen and repaired. most new car owners are not even coming close to reaching the mechanical limits of the short block (not counting oil starved, abused, or overheated engines), so either opinion will turn into a self-fulfilling prophecy.

most folks talking about this will be getting new cars before the insane mileages required to see statistically significant oil related issues.

[1 Lucky Texan]

Originally Posted by the evil twin

May have been a poor choice of words. My real meaning was this: Depending on what they are looking for/ at in the analysis, traces of fuel may still be found even if the fuel is gone. For example, on average gasoline has 8 carbon atoms per molecule and motor oil between 18-34. Perhaps if the analysis shows an abundance of C8 the assumption is that there is fuel. Alternatively, the same could be said for 2,2,4-trimethylpentane (octane) which is derived from the distillation of oil. If there is any trace present (after it has broken down over time) perhaps it becomes harder to burn off as the molecules bond/ disperse.
It is all truly conjecture, I'm a mechanical/ energy engineer. It has been a long time since chemistry on that level. What I do know is that any substance man forces into a particular molecular structure does not want to stay there. Forces of nature and all. That said, I would really like to know.


On the Mobil site they say 5 years "tightly sealed, cool and dry". I don't think a sitting motor would be considered cool and dry
Shelf Life on Opened Bottles of Mobil 1
Also, my supplier for the race bikes oil (Motul) said max 2 years in a garage. I had asked about getting 5 or 10 gallon drums since I go through so much and he said fine as long as I go through it in a year or two.
So I just put 2+2 together. Although, he does want to sell me oil at +$10/qt

hmmm....anyone ever sent in an example of the new oil they put in and then compare that analysis to one at the drain interval?

[Bimmer]

Originally Posted by grossgary

Maybe new oil sitting would be better than having 4,000 mile old oil sit in it for a year?

In an ideal world, yes.

In the real world, where I'm constantly performing triage on my "to do" list, changing the oil way before the recommended interval is pretty far down on the list...

Now I know, at least, that oil is still serviceable at 6,000 miles and 2 years (if not for much longer).

Originally Posted by grossgary

There are a litany of issues that creep up before oil supply related stuff - valve adjustments, head gaskets...

Right, but I worry about (1) sludge in both my cars and (2) the banjo bolt and turbo in my Outback XT.

Originally Posted by 1 Lucky Texan

hmmm....anyone ever sent in an example of the new oil they put in and then compare that analysis to one at the drain interval?

People have done this, but I haven't (see BITOG). If I could have UAO done for free, then I'd do it, but I'm not $30 curious...

[grossgary]

Originally Posted by Bimmer

Right, but I worry about (1) sludge in both my cars and (2) the banjo bolt and turbo in my Outback XT.

right on, good point this should all be qualified by stating that turbo and non are completely different animals in this regard. the turbo's are experiencing oil supply related issues, and synthetics should be used.