To change or not to change.

Joined
Feb 29, 2008
Messages
1,311
Location
the South
That is the eternal question. Factory interval is 7500 miles normal/3750 miles severe service. Oil was changed in March with QSUD 5w30 with a full can of MOS2 with a PureOne oil filter. Currently at 7200 miles. Usage is 75% highway 25% city right now. It can sit for two weeks at a time, then rack up plenty of miles for a trip. I have a 1500 mile round trip next week. I'll be pulling a sample after this trip for a UOA, at about 9K miles, hoping 10K is reasonable for this oil. Fighting the "fresh oil before a trip" bug real badly though.
 
Joined
Oct 3, 2014
Messages
148
Location
Virginia
The TBN of QSUD is not that high, 8 or close to it I think, 9 or 10 is probably its max limit but who knows. I have used it once in my Frontier, seemed to do well over a 5K duration but it was the only one I actually put make up oil with at 3k miles, about a Quart. Not enough to lose sleep over but I did find it odd that it has a low NOACK and was the only brand of synth. that I had to add to. Ran fine though, wont knock it, just don't know about using it for 9 or 10K.
 
Joined
Nov 14, 2013
Messages
2,150
Location
Chicago, IL
Why not pull a sample and run the oil analysis now to see how much life is left, then decide whether to keep it in for the road trip or change it before? I personally still think you're good to go on this oil. Including the road trio, you'll be at around 90% highway miles. And my guess is that the manual schedule is timed for conventional oil.
 
Joined
Aug 13, 2011
Messages
3,001
Location
Lakeside, CA
Originally Posted By: EdwardC
Why not pull a sample and run the oil analysis now to see how much life is left, then decide whether to keep it in for the road trip or change it before? I personally still think you're good to go on this oil. Including the road trio, you'll be at around 90% highway miles. And my guess is that the manual schedule is timed for conventional oil.
If you are trying to figure out what a safe OCI is then do this.
 
Last edited:

Hollow

Thread starter
Joined
Feb 29, 2008
Messages
1,311
Location
the South
Originally Posted By: EdwardC
Why not pull a sample and run the oil analysis now to see how much life is left, then decide whether to keep it in for the road trip or change it before? I personally still think you're good to go on this oil. Including the road trio, you'll be at around 90% highway miles. And my guess is that the manual schedule is timed for conventional oil.
Because if I drop it in the mail to Blackstone Monday, I still won't have the results before I leave Friday. And yes, the manual is based on 2003 conventional oil.
 
Joined
Nov 11, 2010
Messages
9,783
Location
Saskatoon canada
Originally Posted By: jaynissan12
The TBN of QSUD is not that high, 8 or close to it I think, 9 or 10 is probably its max limit but who knows. I have used it once in my Frontier, seemed to do well over a 5K duration but it was the only one I actually put make up oil with at 3k miles, about a Quart. Not enough to lose sleep over but I did find it odd that it has a low NOACK and was the only brand of synth. that I had to add to. Ran fine though, wont knock it, just don't know about using it for 9 or 10K.
Qsud is more than capable of a 10000 mile interval. And initial tbn is hardly relevant,tbn retention is what matters and because of the boron in qsud tbn retention is great. Where exactly are you getting your info,or kinda info or whatever that post was. I suggest reading more while your here and retaining the info gleaned Just sayin Op Personally I'd change it and only because I've got stock and its autumn which is time for me to go thinner in my vehicles due to ambient. If you life in a warmer climate like the south or pacific southwest I'd would leave it alone and change it once your home.
 
Joined
May 28, 2007
Messages
5,579
Location
earth
I would change it in your situation, but it's probably not necessary. What effect does the additive have on your confidence?
 
Joined
Sep 25, 2009
Messages
17,298
Location
OH
Does this old Subie require adds? It would be pretty exceptional if it didn't. Assuming it does, the adds are refreshing the oil's add pack which will allow longer drains if desired. Given what you're trying for, go ahead and run the oil for your trip and then change it and take a sample when you get back. The UOA will give you an idea of the suitability of QSUD for a longer run in your car as you use it.
 
Joined
Mar 24, 2008
Messages
804
Location
A Warm place to live in
I'd say your driving is normal, not severe category. If it's spec'ed 7500 miles for dino oil, I don't see why the QSUD needs changing before your trip. If the oil level is below the dipstick full mark, top it off with more QSUD for your peace of mind, and change the oil when you get back.
 
Joined
Sep 23, 2014
Messages
1,833
Location
Toronto Canada
What do you think is going to happen if you slightly exceed the "life of the oil"? I say nothing. Maybe, just maybe, there might be slightly more wear during the last 1,000 miles. If this wear is %20 greater than usual, it's like an extra 200 miles of wear on the engine. Not a concern. It's not like the oil is going to fall off a cliff property wise. You would learn more with a UOA after the trip.
 
Joined
Nov 14, 2013
Messages
2,150
Location
Chicago, IL
Originally Posted By: Hollow
Originally Posted By: EdwardC
Why not pull a sample and run the oil analysis now to see how much life is left, then decide whether to keep it in for the road trip or change it before? I personally still think you're good to go on this oil. Including the road trio, you'll be at around 90% highway miles. And my guess is that the manual schedule is timed for conventional oil.
Because if I drop it in the mail to Blackstone Monday, I still won't have the results before I leave Friday. And yes, the manual is based on 2003 conventional oil.
Ah, I see, living on the edge, I like it! If you're still considering not changing it, but want a little more peace of mind, you could do like some others have suggested and top it off with a half quart of fresh oil, should boost the TBN a little bit (assuming you're not at the max fill line already). Good luck, and have a good trip, where are you headed?
 

Hollow

Thread starter
Joined
Feb 29, 2008
Messages
1,311
Location
the South
Originally Posted By: fdcg27
Does this old Subie require adds? It would be pretty exceptional if it didn't. Assuming it does, the adds are refreshing the oil's add pack which will allow longer drains if desired. Given what you're trying for, go ahead and run the oil for your trip and then change it and take a sample when you get back. The UOA will give you an idea of the suitability of QSUD for a longer run in your car as you use it.
Nope, no top up required. I've had the car since 63K and like clockwork it uses about .25-.50 quart per 5000 miles. Dipstick is still fine at this point. Manual specs for 4.5 quarts, but I've always put in the even 5. With QSUD being a Dexos1 oil I'm pretty confident in it.
Originally Posted By: EdwardC
Good luck, and have a good trip, where are you headed?
East TN - Chicago and back. FWIW, the Lubry-Moly MOS2 is to see if the higher Moly helps the classic Subaru piston slap quiet down some. MPG improvement is within margin of error, so the jury is still out if I'll run it again.
 
Joined
Jul 17, 2005
Messages
20
Location
USA
I'd change it. Given the longer mileage interval nature of QSUD, you will probably be ok. If you are a typical BITOG OCD (like me) then go with the change. As for me, I would rather take a longer trip on clean oil. The thought of dirty oil scrubbing the cylinders over 1500 miles at high speed gives me the shivers. If you leave it in please publish the oil analysis so we can see how it is performing.
 
Top