I did my first oil change on my '95 850 NA. Should've done it when I first bought the car, but the previous owner had it done before sale (legit looking sticker, at least) and I just waited.
So I buy all the supplies, drain the old oil, and go to remove the filter when I notice that it's actually smaller in diameter than the new one I bought.
After confirming the one I bought was the correct one, I looked up the part number for the smaller one and it turns out it was a Valvoline VO25--a filter made exclusively for Chrysler cars. Not only that, but it had been on there for nearly a year so even if the oil had been changed before I bought it they didn't change the filter. The old oil looked pretty rough as well.

Now I have a fresh (correct) filter and oil in there, but I'm worried that having an old incorrect size oil filter on there for so long may have done some permanent long term damage to the engine. Thoughts? Also one guy I talked to said I should wait a month, use seafoam and then do another oil change, then wait another month and do another seafoam/oil change. Sound legit?

Thanks everyone.

I feel like kicking myself for not changing the oil immediately after buying it...I changed the freaking timing belt but put off something as simple as an oil change because I trusted the previous owner and a sticker. Lessons learned.

 

If the oil you drained out did not look to be overly dirty or sludgy I would simply run the vehicle for say 3,000 miles with the oil and correct filter you now have.
For peace of mind i would ensure the subsequent oil and filter change is brought forward to act as a flush cycle, after which I would resume normal mileage/time frame maintenance going forward.(approx' 5,000miles)

Although you left the oil change initially and trusted the previous owners servicing advise you must surely have checked the dipstick for oil level occasionally where any especially dirty appearance would have been evident at that time.
As nothing appeared amiss? when checked you should be okay without sea foaming.

 

If you didn't have a low oil pressure light then you should be fine. One of the problems with after market filters is they can lower the oil pressure to the point the pressure light comes on at low RPMs. The filter is not specific to Chrysler - it happens to match to the RWD red block Volvo's 240s/740s/940s etc, so it would fit but doesn't meet other specs like max flow rate for the 850s (particularly the higher revs and turbo models).

Going forward, I'd recommend a few things - 1) hold off on the Seafoam for the time being unless you have specific problems - ie VVT errors, ticking noises, and notice sludge in the top end (ie peek in the filler cap and see if there's anything built up. Staining is normal - so the metal should have a orange/brownish color but nothing caked on. If you do a Seamfoam treatment you may loosen enough sludge to clog your PCV/flame trap. If you are planning to change the PCV then its ok as it can help keep the new one clean. 2). Consider using a high mileage oil from Castrol, Penzoil, Quaker St etc which has seal softeners, particularly if planning a conversion to synthetic. 3) use OEM Mann oil filters (w917). They have a check valve which helps keep oil in the upper parts of the engine after shut down. 4) if you decide to stay on dino oil, change every 3-5K miles or six months (which ever comes first). If you move to synthetic, you can go 2X that.

 

Thanks guys. Never had any low oil pressure lights, and while the oil was a little rough looking from my limited experience it wasn't sludgy or thick.

I figured the two back to back seafoam treatment + oil changes sounded extreme but it was from a guy at Orielys--glad I asked here to confirm my suspicion first.

Also, I guess that makes me a little less mad at Valvoline that the incorrect filter is at least used on some Volvos, though it's still a reminder of why to always do my own changes or use a trusted place.

I will keep an eye on the oil and also for the other things mentioned and then do a change at 3000 using the filter/oil you suggested.

Thanks again!