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#4710006 - 03/28/18 08:16 PM What weight is best?
Mar57 Offline

Registered: 12/18/12
Posts: 48
Loc: Connecticut
The car is a Mazda Miata. Owners manual calls for 90wt. gear lube in the diff. I can't find any straight 90wt. lubes. So the question is can I use a 75-90wt. lube? Mobil 1, Valvoline etc. make a synthetic 75-90wt. and a synthetic would be my preference if that weight can be used. What do you guys think?

#4710016 - 03/28/18 08:22 PM Re: What weight is best? [Re: Mar57]
spasm3 Offline

Registered: 05/30/10
Posts: 8440
Loc: North Carolina
I would check what the dealer has. If its 75-90 or 80w90 as well, then use what you want. If they have a straight 90wt( i doubt it) buy that.
13 elantra 67k 5w30 QSUD
03 chevy avalanche76k synpwr 5w30
01 saturnsc1 185k synpwr rebuilt
17 mazda cx-5 2200 miles m1 0w20/0w40 mix

#4710037 - 03/28/18 08:34 PM Re: What weight is best? [Re: Mar57]
Chris142 Offline

Registered: 06/05/03
Posts: 16534
Loc: Deplorable in apple valley, ca
Any 75w90 or 80w90 is fine.
02 Wrangler super-s 10w30
87 F250 proline 15w40
04 Tahoe super-s 10w30
Z400 Lucas 10w30
KLR250 Maxima 10w40
Can am maveric edge 5w40
57 case tractor 15w40

#4710052 - 03/28/18 08:55 PM Re: What weight is best? [Re: Mar57]
Warstud Offline

Registered: 09/02/05
Posts: 5205
Loc: MIchigan
Originally Posted By: Mar57
Owners manual calls for 90wt.

They don't mean straight 90wt.

#4710058 - 03/28/18 09:05 PM Re: What weight is best? [Re: Mar57]
Mar57 Offline

Registered: 12/18/12
Posts: 48
Loc: Connecticut
"They don't mean straight 90wt."

If they didn't mean it, why print it? That's what the manual says so why should someone have to try to interpret what they mean?

#4710064 - 03/28/18 09:17 PM Re: What weight is best? [Re: Mar57]
donnyj08 Offline

Registered: 08/12/12
Posts: 2996
Loc: Cincinnati
Any 75w90 synthetic will do.
2008 Silverado Z71 LT 89k Maxlife FS 5w30
2010 Ford Escape 163k PP 5w20
2016 Yamaha XSR900 10.7k, Rotella 15w40 Yamaha Filter.

#4710066 - 03/28/18 09:18 PM Re: What weight is best? [Re: Mar57]
Warstud Offline

Registered: 09/02/05
Posts: 5205
Loc: MIchigan
They mean 75w90 or 80w90 and not 75w140. I'm using these as examples because there the most common.

#4710067 - 03/28/18 09:18 PM Re: What weight is best? [Re: Mar57]
ctechbob Offline

Registered: 06/12/04
Posts: 131
Loc: Athens, GA
Agreed, never had a lubrication caused problem out of a 75w-90 or 80w-90 in my 91, even with the 1/2qt capacity and the track beatings it took.
2008 Acura TL Type S - 140k
2003 Honda Accord V6 - 220k
2000 Honda Accord I4 - 300k
Current Oil - Milesyn SXR5W20/5W30
Current Filter - Partsmaster 61334

#4710105 - 03/28/18 10:20 PM Re: What weight is best? [Re: Mar57]
Reggaemon Offline

Registered: 02/19/07
Posts: 319
Loc: Pennsylvania
What year is the Miata? In the 3 owner manuals that I checked NA,NB and NC.
The specs were...GL-5 SAE 90 80w-90 and 75w-90.
Everyone I know is using 75w-90.

#4710252 - 03/29/18 07:33 AM Re: What weight is best? [Re: Mar57]
Donald Offline

Registered: 03/21/04
Posts: 20248
Loc: Upstate NY
Less weight is definitely best. I am trying to loose weight.
2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)

#4710321 - 03/29/18 09:01 AM Re: What weight is best? [Re: Mar57]
artificialist Offline

Registered: 09/23/07
Posts: 8542
Loc: Florida
Many Japanese cars call for SAE 90 gear oil, but I never had a problem when replacing it with conventional 80w90 or synthetic 75w90. In the repair shops where I worked, we just used whatever XXw90 gear oil was on the shelf.
2010 Lancer Ralliart Sportback

#4710768 - 03/29/18 06:00 PM Re: What weight is best? [Re: Mar57]
JLawrence08648 Offline

Registered: 01/20/17
Posts: 165
Loc: NJ
Always synthetic in that heavy weight oil, doesn't matter the weight as long as it's close, which it is.