wemay,
parts place in town had Penrite 5W30 "racing" oil (PAO/Ester, loads of zinc and boron), on closeout, and I got the last 5L for $25...I snatched it.
Later, I bought their last M1 5W50 for $26, and planned my super brew.
Made a 4L/3L blend, for a "5W40", thinking to get HTHS around 3.6ish...started the OCI nearly a qt short, to fine tune. That was May last year, before we tripped the US for a month.
Meantime, I ran 5W20 synthetic (Nulon, no teflon in their engine oils, but have MoDTC) in my mower over winter - wasn't cold enough to kill the grass, so I tried 5W20 (didn't like the "knock" that the engine made to first couple of power strokes)
Talking to Penrite, they confirmed the HTHS of the Racing 30 was 3.4, so my brew was too thick, I had room in the sump, and a 5W20 that I no longer wanted to play with in my mower.
So filled to the full mark with the 5W20 to get closer to my target.
About that time, I started reading more on what the standard offered.
http://www.bobistheoilguy.com/forums/ubb...922#Post3503439
My Nissan normally drops a litre quite suddenly at 7,500 to 8,000km into an OCI, 10,000km OCIs on the diesel engine...it did it this time at 5,000km.
Only member of the original brew that I had left in the stash was M1 5W50, and I didn't want to add that.
So added some Caltex C3 that I had (had worked out that a parts chain synthetic was Caltex C3 synth, so bought it at the time)...topped up with that.
Then chickened out, concerned that the usual pattern of consumption was changed with that brew before the Caltex was added, and not going to do a winter on a more frankenbrew...so dumped it at 5,000 and a handful of km...Edge 5W30 A3/B4 replaced it, and a new filter.
Have been playing with 0W, 5W, 10W, and 20W of various grades (20, 30, and 40 (and 50 and 60) in my freezer (-20C), just to see what happens, and the aged in an engine synthetic brew is pretty poor compared to a semi 10W30, not as bad as a good SAE 30, and lots worse than M1 5W50 (which was indistinguishable from the 5W20 in the same "test").
Not scientific in any real way except for the fact that the freezer is -19 or -20 C pretty consistently. The cold temperature performance of a finished lube is allowed to drop a grade and still remain in grade, and I haven't played the game with used oil from that vehicle before.
Would love to have an MRV in the shed...alas I don't.