GeneralDisorder

What's wrong with it? Center diff? Just replace the diff and bearings. They all have that problem. Used isn't going to be a good option. GD

Yes.

How do you know the engine is stock? If it's got a 3 bolt strut, and it's an 87 then it's a 3 door coupe. The STD hatch wouldn't have a 1600 badge, and in 87, a STD hatch wouldn't have a dual range. In fact nothing EVER came with a 1600 and a dual range that I'm aware of. The 4 speed D/R came out in 81 and was only ever equipped on 1800 engines. This is probably an 87 carbed 3-door coupe, with a 5 speed D/R that someone swapped in an EA71 and stuck a badge on it. GD

12 degrees is a bit to far, and with two other local sources of temperature including one being a similar model Subaru I would then be willing to agree it's probably a bad sensor. Overwhelming preponderance of evidence suggests you have a legitimate complaint.

The variable is your PHONE APP. That's the variable. You have no idea where they get this information. It's probably from a national weather service and is second hand or third hand or more levels removed from the reality of the temps on the ground. GD

Weather apps from your phone?!? C'mon. That's not science. You have no idea where they get this information, if anything it's a weather station on top of a building somewhere far from the surface streets. Air temperature is not equivalent to surface street temperature. FAIL. Come back with real data. Get a temp sensor and mount it near the factory unit. Or this discussion is worthless. GD

Silicone. That's what the orange OEM one is. Close enough (silicone comes in many colors - the color means nothing). Get one in Viton if you prefer. Viton or Silicone will last longer than Buna-Nitrile. For that matter you could just use a good tight fitting o-ring of 2mm diameter from a generic kit and likely be fine for the remaining life of the EZ. You can get a kit and make your own also. I have made many o-rings for such things as the rear cover gasket on the STi power steering pumps (not available)...... lots of options. I would just get a generic kit of Viton o-rings, test fit a couple and pick the one that fits snug. This really isn't rocket science.

McMaster-Carr. 5233T152 GD

Best to keep it under 170. But up to 200 isn't likely to hurt it either if you have good fluid.

They are NOT torque to yield bolts. Subaru has never used TTY head bolts and there is no mention of replacement in the FSM. Just clean them with mineral spirits, or a parts washer. Do not use a wire wheel or brush or anything abrasive - it will remove the anti-friction coating. If any have pitting damage or rust replace only those. Reuse the rest. Lube them with Amsoil assembly lube. Chase the block threads (an old head bolt with a couple slots cut up the threads works well), and run the bolts in and back out a couple times (head off) with the assembly lube to pre-lube the block threads and check for any binding. Reapply assembly lube to the bolt for final torque. If you feel any binding or tightness to the threads STOP and asses the situation. If you seize the bolt in the block and it breaks off you are totally F'd.

204 is normal - that's where the fans come on. Though when driving it shouldn't need the fans so if the system is working efficiently it will stay usually below the fan set point if you have good airflow across the radiator.

It probably is. The tolerance on that sensor, which isn't mission critical, is probably +/- 5% around average ambient temps (70ish degrees F). You appear to be even closer than that. There are a LOT of variables in play when it comes to sampling ambient temperatures. What are you calibrating the car's sensor against? Conditions above asphalt on a sunny day WILL be different than 20 yards away over grass for example. It is not that simple and only a simpleton would believe it to be that simple. This is not a nuclear reactor - the sensor is a $0.10 thermistor inside a plastic housing designed to be a gadget in a consumer product - one that in 99.99% of prospective buyers will never be questioned. The problem is your expectations and your understanding of the variables at play in taking these measurements. It's actually amazing the thing reads within 2-3 degrees. That is plenty accurate for the needs of anyone performing the activity of driving. GD

Ground temps and ambient air temps are often not in agreement. Freezing rain for example.... it's not as useful as you might think. If it's within 5 degrees of freezing either way you should ASSUME there could be ice. No judge is going to absolve you of idiotic behavior because your cars ambient air sensor said it wasn't freezing. LoL. Useless..... GD

Generally lower is better for trans fluid. To a point of course. I run my 700R4 with only independent coolers and on most days it doesn't get up past about 130-140 degrees. Indeed it shifts harder and engages more positively with lower fluid temps (higher line pressure). Trans builders will tell you that anything over 170 will shorten the auto transmission clutch life. If you run no coolant heat exchanger definitely use synthetic as it will perform and flow better at lower temps. GD

As you observed the readings from that sensor really don't matter. What do you propose doing about it? Unfortunately the dealer is unlikely to do anything. Complain loudly enough and maybe they change the sensor - likely leading to no resolution since it's probably a design flaw in the location of the sensor. It's pretty unlikely the sensor is actually bad on a 2019. Only permanent solution I can think of is trading it in. Or therapy. I mean really what's the difference what the exact temperature outside is anyway? .....100 years ago people actually walked outside or opened a window and checked the weather. Doesn't really seem all that difficult to me. The actual number doesn't seem all that useful. No car I have ever owned personally shows this information and I can't really see how it would be useful. My phone tells the weather and the forecast too so..... GD

Lubriplate assembly lube is what I use on rods, mains, and cams. Any journals. Would work for the seals also. The Dow 111 really protects the seals and especially o-rings. Coating the nitrile rubber o-rings in 111 keeps oxygen from getting to the rubber and that's really what is responsible for making them hard and crack. Oxygen and heat. 111 is amazing stuff to have on hand in any garage. Besides lubricating any and all seals, oil filter gaskets, etc - it is also a perfect dielectric grease for all electrical connections including plugs and wires. Don't lubricate the OD of the seal. It can and will pop back out. Using the loctite 248 stick will provide for smooth installation and quickly cure making it almost impossible for the seal to come back out on it's own. Indeed - quite a lot of force and red hot cursing will be involved in its removal. GD

Lube the ID of the seal. Dow 111 is my preferred lubricant. If you really want to make sure the seal never walks out, run loctite 268 around the OD before you put it in. The next guy will hate you though. GD

No. You just use the complete 2.5. Using the 2.2 heads is stupid.

yes

Yes that's the part you need. 4 per side (8). Also get 16 of part # 13396. The lack of readiness completion is normal for 95/96 models and was addressed by filing a variance with the EPA. It is a known and ignored issue at all testing stations nationwide. GD

The oil drain back passages are huge. Like 1.5 x 3 inch.

It's half of one of the spring washers used to separate the rocker arms. It just fatigued and broke - the other half is somewhere. Way too big to get sucked into the oil pickup so not really a problem. Just pull the valve covers, and looks like its time for some maintenance. Replace all those washers and a good time to do the lifter o-rings. GD

Buy a new idle air control valve from Subaru. GD

If debris got into the system, it's quite possible to plug all the injectors. You need to find out where the debris came from. Definitely a good case for an additional inline filter in the mean time (serviceable, 40 micron element ought to do the trick). GD

Correct, your car comes equipped with headlights from the factory. Good observation. GD