Originally Posted By: HighlanderBH
Only Motul oils are available here. The Honda MTF 06 (possibly 75W80) is available too, but the gear shift is notchy when hot. And the Honda it's a mineral oil.
Notchy gear shift when hot would be a bitter pill to swallow for me personally, as most transaxles are driven 'hot' most of the time other than the initial 5 minutes or 10 after cold start in a winter season.
Heck, there isn't any winter season in Brazil or SE Asia.
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Considering that the Motul GEAR 300 75W90 (fully synthetic) is superior to the Motul Motylgear 75W80 (blend), what are the possible problems when using 75W90?
You are spot on in suggesting Motul Gear 300 75W90 being fully synthetic, is superior to Motylgear 75W80 as far as base oil is concerned.
Besides , the thicker minimum oil film thickness MOFT in a 75W90 could potentially prolong or double components life of say, bearings and gears within the transaxle.
Possible problems ?
Absolutely zero problem vis-a-vis 75W80 for tropical Brazil as there isn't a winter season that could potentially lead to cold shift issue, an issue which I believe had often been unjustifiably 'attributed' solely to a thicker 75W90 in manual trans or transaxle on this board.
As you noted above, original Honda MTF as recommended by OEM and happens to be 'thin' could cause shift issue too!
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Would a 75W90 oil cause premature wear or any other failures?
Absolutely no.
Physics says, the thicker MOFT in a 75W90 could prolong components life instead.
Assuming identical add packs in both oil grades , could a 75W90 performance lasts longer ?
I would think so, if it matters.
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On the other hand, would the Motul Motylgear 75W80 be a better choice, because it's 75W80, even if it is blend?
In physics, no . Other than the 'elusive' cold shift annoyance, which isn't an issue in tropical Brazil.
Edit:Oops, miss your post above.