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Motor Oil Viscosity in a very old Miata

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May 06, 2025, 01:01 PM
trapper189
Motor Oil Viscosity in a very old Miata
Elaborating on what ridewv said about conventional 10w30 and sheer of the VIs, my understanding is that most synthetic 10w30 oils don’t use VIs and thus aren’t subject sheer to the extent that conventional oils with VIs are. It’s one of the reasons synthetics can go longer between oil changes.

A synthetic 10w30 is really a straight 30 weight oil at 212 degrees. The reason it’s a 10 weight oil at 104 degrees is that through the process of creating it, paraffin is either removed from the base stock or a base stock is used that doesn’t have paraffin to begin with. The paraffin in conventional oil causes the oil to thicken as the temperature gets lower.
May 06, 2025, 01:10 PM
P250UA5
Can't add to the oil talk, but that's a mighty clean Miata. Jealous.
The NB is probably my favorite [with a 5spd, didn't like the 6spd in the NBs], but a clean NA wouldn't be far behind it.
Can't afford a ND2 or later.




The Enemy's gate is down.
May 07, 2025, 03:36 PM
ShouldBFishin
Congrats on the new fun machine!

I've been running synthetic 10w30 (Mobil 1) in my '91 that I picked up a couple years ago. Just rolled over 60K on it the other day.



May 07, 2025, 07:14 PM
Lucnik
quote:
Originally posted by SIGfourme:
I loved my Miata-best convertible for the price. Make sure you unzip the rear window b4 unclamping the convertible top. Drive and enjoy.

When I had my 97 I used a piece of swimming pool noodle to prevent a crease in the plastic backlight. Never had to unzip it.
May 07, 2025, 11:26 PM
sjtill
Glad to see you’ve taken care of the transmission and differential lube.
My 2005 S2000 was sitting for about a year and a half and (at least according to the Honda dealer) the fluids were pretty grotty.


_________________________
“Remember, remember the fifth of November!"
May 08, 2025, 05:46 AM
r0gue
Both the fluids looked surprisingly good, though I've no expertise to make such a statement. I'd say it is shifting better. It should, as the gear oil (Ford Motocraft GL-4) was $50 a quart!




May 08, 2025, 06:10 AM
bob ramberg
Redline MTL is what I used in the trans. significantly improved shifting. $24 qt.


Bob
Carpe Scrotum
May 08, 2025, 07:26 AM
P250UA5
Redline in the trans on my Midget, too.
Don't recall if I used it in the diff, too. Mightve been a valvoline product.




The Enemy's gate is down.
May 09, 2025, 06:03 AM
calugo
I would stick with whatever oil the owners manual indicates, don't think you can go wrong if you do.
May 09, 2025, 05:45 PM
SHOOTIN BLANKS
Also off topic... Are you using a cat as a wheel chock?


___________________________
"Opinions vary" -Dalton
May 10, 2025, 05:17 AM
r0gue
quote:
Originally posted by SHOOTIN BLANKS:
Also off topic... Are you using a cat as a wheel chock?


That's Maxwell House. He's "my" feral cat, (that is isn't actually feral anymore).




May 10, 2025, 06:36 AM
John Steed
I would listen to the voices of experience (Bob Ramberg and ShouldBFishin) and follow their advice.

I agree with the gentleman who said the chart in that manual is incorrect. I have seen similar mistakes in the oil viscosity recommendations in manuals. If you look online, you may be able to find an electronic version of the manual from the next year or so with a corrected chart.



... stirred anti-clockwise.