Blizzaks, 0W40, Snow and Ice…Nice!

[OK-944]

Had the Blizzak WS-90’s out in snow and ice for the first time in my ‘87NA…and am very impressed! Took a long, curvy, icy dirt-road hill…coming into the bottom turn from the main road at a good speed with just a bit of a fishtail, which came very nicely under control. Then into a bit of slush…and all is well. Not exactly my wife’s Forester, mind you…but very respectable. Also, these Blizzaks, which are an upgrade from the earlier WS-80’s, are surprisingly good on dry roads. A bit of road noise, but overall pretty responsive.

As for the Mobil 1 0W40…this really makes a difference at startup, and I sense that the car purred along just a bit more smoothly in general at these low (15 F) temps than with the 10W40. Good oil pressure throughout the run. Now…fingers crossed that the oil stays put - or at least…if there are a few drips, that nothing comes out through the new rear main and messes with the (also new) clutch!

[walfreyydo]

OW-40 is very low for the temperature range (even now in winter). I would be concerned that running this low weight of oil could damage bearings/cam journals. I see quite often people making the wrong assumption of running modern oil weights meant for modern engines to our older cars. Keep in mind that modern engines have tighter tolerances than they had back in the 80s allowing for much thinner oil to be run, which improves its gas mileage. Modern engines can get by running 0W oil because of this (like my wife's 2016 honda). I only say this because I know you have a freshly rebuilt engine, and wouldn't want you to cause any premature wear, especially during startup when there is not much oil there to lubricate the bearings because of its low viscosity.

Edit: For reference here is the oil viscosity chart recommended for the 944 from the owners manual.

[Jfrahm]

0w40 should work like the bottom oils on that chart but with a longer line to the left. 40 weight oil that acts like a 0 weight at low temp. 0w40, 5w40, 10w40 and 15w40 should all act like 40 weight at 100C. Should.

However a lot of the viscosity range is IMO marketing and what IMO is important is the viscosity spec at 100C and how well the oil holds up over time. Oil with a lot of VI improver can have a shorter lifespan. It might also not be as good at being oily as an oil with a narrower range.

[OK-944]

Thank You.

I went back and forth about this - pulling my hair actually…as to whether to leave in the 10W40 or take a leap and try the 0W40. So I dug around a bit, finding references from other 944 folks who seem to swear by this particular Mobil-1 0W40 “FS” formulation, which touts a decent (1100ppm), yet not quite Cat threatening level of Zinc (which should equate to protection at startup), is both approved by Porsche (Porsche “A-40” spec, whatever this means) for their older cars and specifically recommended for my 944 by Mobil for cold weather use. But is this just hype?

I do get a slight sense that upon first (cold) startup with the 0/40, there may be just a very slight friction related sound/feel…whereas with the 10/40 this was more of a shudder. But does this mean anything?

I can remember, during the rebuild…carefully peeling the plastigauge off of the main journals and feeling a thickness that, while perfectly mid-spec for my car, I could see as being a bit “loosey-goosey” for something off the shelf within the last year or so. And I do see lots of 944 folks using 20/50 - but this seems to hold mostly for cars that live in hot climates and/or are tracked…neither of which hold in my case.

There are those who say that using anything less than a first-rate synthetic oil would be downright irresponsible…even for a thirty-five year old, flat tappet engine - and oh…of course, go for the thinner oil for winter because…hey, its synthetic! But is this correct?

The answer here is (with no disrespect)…that this will make me lose a bit more sleep tonight is my guess…but will I get my car back on my lift tomorrow and go back to 10W40? Truth be told, I’ve gotta think on this…just a little more! But just the same…thanks!

Edit: for example...just found this post in the Jalopy Journal: "There are 2 choices in Mobil 1 for a flat tappet. The 0w-40 has 1100ppm and 15-50 has 1300ppm, both will work great with a flat tappet motor. All of the other weights are low zinc now, so stick to these two weights if you run mobil 1!!!! I've run them for years in my OT Porsche 968 motor thats a DOHC setup that runs flat tappets to activate the valves in the head. Thats been zipping up to 7 grand for years now. I use the 0w-40 in the winter as it flows when its really cold and the 15-50 in the summer to help keep the #2 rod bearing happy when running hard. I'll be running 0-40 in my 392 when the time comes."
AROMINUS, NOV 10, 2020

Edit: Just found this from an LN Engineering's "Tech Tuesday" posting:
"The introduction of Porsche Classic's own line of oils replaces Mobil 1 0w40 and other listed Porsche A40 approved oils as the recommended fill for 1984 and newer models." They go further by saying that previous "Porsche Approved" A-40 motor oils are no longer guaranteed to be backwards compatible, due to recent changes in formulations.

At this point...I'm very tempted to buy into Porsche's mindset, cut to the chase, and spring for some Porsche Classic motor oil, 10W50 as formulated for the 944.