For me, maybe the wd green 265 ssd was not good enough to run catalina at full speed.
i had to delete the OS on the same MBP 12 due to the hot sensitive to the touch temps,
now i remember that was running that at max tho.
I know I’m necromancing your comment here, but there’s another factor really worth taking into mind with SSD models and performance, especially on the later, unsupported builds relying on, increasingly, APFS:
The marketing of WD’s Green line of SSDs is meant to mimic the low-energy consumption of its retired, Green HDDs (which weren’t speed demons, but they ran cooler due to how they were designed to spin down to a low RPM when idle and to rely on variable-demand rotation — which is why they were never rated at 5,400 or 7,200 rpm, but mostly moving about somewhere in between).
The Green line of SSDs, however, are now tiered as WD’s entry-level SSD. WD Green, unlike WD Blue, Red, and Black SSDs, lack a DRAM cache. This is where the price savings comes in/from.
What this means, plainly, is for non-sequential reads and writes to the SSD, everything bottlenecks much sooner without the presence of that RAM cache. It’s not unlike the way a computer itself bogs down when running a bunch of small processes concurrently, except with really low RAM: it bogs down and bottlenecking ensues, relying on the hard drive to handle memory caching.
At the device level, this is similar with SSDs. Without DRAM onboard to SSD, the drive is closer in analogue to, say, a Mac trying to run Snow Leopard on less than 1GB RAM from a HDD: it
may eventually pull up the Desktop, but you’re going to hear that HDD inside chugging hard with all the swapping. You won’t once you add 7 or 15GB more to the system.
I’m unusually familiar with the WD line because it is what I buy and rely on for many of my Macs, both as SSDs running MacBook Pros and HDDs for archival storage in my Power Mac G5. But Seagate and the SanDisk brand (the latter now a brand under WD) also have their entry-level SSDs, which also lack that DRAM cache.
Many of the funky-named SSDs folks here have used to speed up their old PowerPC Macs — Zheino, DogFish, iRecdata, etc. — are cheap precisely because they lack the DRAM cache (as dynamic RAM, when compared against non-volatile RAM, is still more expensive, byte-per-byte).
All of this to offer: throw in at least a WD Blue SSD (or Seagate/SanDisk counterpart) instead of that WD Green, and leave the WD Green for data storage only. You’ll find — yes, even in Mojave, which is what I use on my late 2011 MBP, running two internal DRAM-cache SSDs — the battery life will probably improve: the drive controller isn’t having to work as hard for a lot of the constant, small-data-transfer tasks of, say, browser tabs. And with APFS, which takes snapshots of changes to contents, that DRAM cache will also make a difference.
My Macbook pro i7 is from 2012 and does not get hot with Mountain Lion but uncomfortable with Catalina,
so scientifically.... the thermal paste SHOULD be fine,
BUT
since this is a 2012 does thermal paste fade?
It absolutely does. Paste from that far back is basically just crumbly substrate of its former self, with ductility at a fraction of what it was, as well as its heat-transferring efficiency.
I’m like
@Certificate of Excellence here, except for lesser-used, old, cooler Macs — like the slower PowerPC models I have — it might be closer to five or six years between when I clean and replace the paste. With my early 2008 MBP or 2011 MBP (both the late 2011 and its prdecessor, the early 2011), I replace the paste around every two or three years, mostly as a preventive way to keep things cool, especially since these are not only legacy systems, but also dual cores handling stuff typically optimized these days for four cores or more.
the process seems straight-forward and i did that in 2015 several times on other's Macbooks
Although i'm reluctant to fix something that is not broken, and will never use Catalina again.
while others who make online vids always re-paste any old macbooks they buy and fix.
hmmmmm.....
Try to think of things like replacing paste, dusting out the innards, especially the fan elements, and even cleaning out the keyboard assembly on MBPs as preventive, long-term, and necessary
maintenance/upkeep — not a “fix” or a “repair”. In a mechanical sense, like bicycle upkeep, this is like cleaning your drive chain and re-packing axle/bracket bearings with grease every few years. Your Macs will respond to the difference by not running nearly as toasty.