Lots going on in Miataville this week...
It all started Wednesday night. My wife calls, and says there's something wrong with the NC. She says she went to get something to eat, and when she came out, there was oil and "green stuff" all over the driver's front wheel. She said she got in and started it and it made a bad noise, but she was able to drive it back to her office. I ask if the noise was like spoons in a garbage disposal, and she says yes... Uh, oh...
I leave work early, run home and get the truck. Drive to the storage yard and pick up the trailer, then make the hour drive to her office. There's a trail of oil leading to her parking spot, and oil all over the car and ground. I look under the hood, but don't see anything obvious. We load the car in the trailer, bring it home, and call it quits for the night.
My usual weekend is Thurs-Sat, so Thursday morning I get the NC up on stands in the garage to take a look. I start with the obvious suspects... oil drain plug is tight. Oil filter... loose, and hanging on the threads. Looking at where the oil sprayed, it looks like the obvious source. I'm thinking WTF! I had done oil/filter about 1000 miles ago on the NC, the 12th oil/filter change I'd done on the car. I've done countless oil/filter changes over the years and never had a filter or drain plug come loose. Oh, well, guess it can happen to anyone.
After further interrogation, my wife had said it made the bad noise on startup, and then went away when she drove the car, so I'm thinking maybe it was just the filter rattling and we may have gotten lucky... So I make a run to get a new filter and some oil. At the parts store, I get a filter for the NC, and also for the NB. Parts guy gives me the filters, and it clicks...
When I did the previous oil change, it was the first time I had ever bought filters for the NC and NA at the same time. Parts guy, says they're the same filter. I say, "huh, didn't realize that". Guy gives me two filters and I go home and change the oil in both.
Guess, what... they're not the same. I realized this immediately when the parts guy (on this week's trip) gives me two different filters.
Turns out the NA/NB filter is the same thread, and will even torque down properly and not leak (initially) on an NC. But the gasket eventually pushed out and it came loose. As I noted before, this was my 12th oil change on the NC, and I have a routine. The old filter comes out in a wad of paper towels, straight into a freezer bag, otherwise you get oil all over the crossmember. The new filter is primed with oil, sitting next to the jackstand ready to go. As such, I never directly compared the filters... lesson learned.
So, new filter on, cheap dino oil in (why fill with M1 when it could be toast?) and fire it up...
Sounds... normal. No knocking, ticking, screeching or any indication it sustained any damage. So, I took it out and tried to break it. Run through the gears, rev limiter several times, pull from idle, decel from high rpm. If it's gonna go, I want to know. Nothing. Runs great. Big sigh of relief...
Wife drove it to work on Friday, ran fine. Yesterday, I swapped the oil out for M1. No signs of metal in the oil that came out.
I think we dodged a bullet!