Anyone run an analysis of stock gear oil?

Jon · 06-23-2005, 07:20 AM

Just wondering if anyone has sent in a sample of their factory-fill gearbox oil for lab analysis.

Reason I'm asking--someone had a theory that the stock gear oil is actually lighter than the ubiquitous 75W90 replacement oil. This makes sense on two levels:

1) Subaru uses the lightest of the reccommended engine oil weights (5W30) as factory fill. Why wouldn't they do the same for the transmission, since their goal seems to be minimum friction for maximum fuel economy?

2) I'd swear that the 'box was slightly easier to shift (by that I mean quicker syncro action) with the stock fill than with the 75W90 I have in there now.

STi05' · 06-25-2005, 12:30 AM

I wouldnt mind seeing these tests either

Jon · 06-26-2005, 09:44 AM

If anyone's planning on draining their factory-fill gear oil anytime in the near future, I'll be willing to pay the $20 to have it analysed if you'll post the full results here.

This is who I use: http://www.blackstone-labs.com/standard_analysis.html

**tcam33** · 06-26-2005, 06:46 PM

I'll send you a sample. Fire me your addy. I'm changing the box's oil soon as well as the rear diff. fwiw the dealer here recommends Motul gear 300

Rev · 06-26-2005, 07:11 PM

Interesting ... When I filled with Motul 75W-90, tranny feel improved a lot. Especially during the winter, I myself didn't like the factory fill so that's my reason for switching it.

CoreySTi04 · 06-27-2005, 02:29 PM

Definately let us know what you find out.

I switched to Mobil 1 syn 75W-90 and had nothing but problems. The theory around here was that it was actually too slippery to get the syncros up to speed. I was missing shifts like it was my job. Switched to regular Valvoline 80W-90 and no more problem shifting at higher RPM. I never used to miss shifts and now I don't again.

I guess the moral of the story is stick with regular oil or play with friction modifiers if you're running synthetic.

CoreySTi04

Jon · 10-25-2005, 09:46 AM

Here you go. Thanks to tcam33 for the sample.

Interestingly they say it might be a 75W90, but the viscosity is low...

**tcam33** · 10-26-2005, 07:26 AM

Thanks for doing the analysis

Interesting comments I expected to see the wear metals a lot higher. FWIW the oil had 9,200mi on it and it was a straight factory fill no additives on my part

SupraSTi · 11-28-2005, 07:50 AM

I just checked the level of mine after an oil change and I'm right at the low mark on the stick. Just picked up an 05 STi with 7K miles now.

06-23-2005, 07:20 AM	#1
Jon STI Driver Location: SE PA Posts: 261 IWSTI Addict since: Jan 2004 Trader Rating: (0)	Anyone run an analysis of stock gear oil? Just wondering if anyone has sent in a sample of their factory-fill gearbox oil for lab analysis. Reason I'm asking--someone had a theory that the stock gear oil is actually lighter than the ubiquitous 75W90 replacement oil. This makes sense on two levels: 1) Subaru uses the lightest of the reccommended engine oil weights (5W30) as factory fill. Why wouldn't they do the same for the transmission, since their goal seems to be minimum friction for maximum fuel economy? 2) I'd swear that the 'box was slightly easier to shift (by that I mean quicker syncro action) with the stock fill than with the 75W90 I have in there now. This ad is not endorsed by this member. Please register or login to hide this ad. Last edited by Jon; 06-23-2005 at 07:23 AM.

11-28-2005, 07:50 AM	#9
SupraSTi Junior STI Driver Car: 97 Supra Fav Mod: 750RWHP Location: Algonquin, IL Posts: 60 IWSTI Addict since: Nov 2005 Trader Rating: (2)	I just checked the level of mine after an oil change and I'm right at the low mark on the stick. Just picked up an 05 STi with 7K miles now. This ad is not endorsed by this member. Please register or login to hide this ad.

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06-25-2005, 12:30 AM	#2
STi05' The Next Petter Solberg Car: 05' STi CGM/Silver Fav Mod: Recaro Sports Location: Mercer Island, Wa Posts: 973 IWSTI Addict since: Oct 2004 Trader Rating: (1)	I wouldnt mind seeing these tests either

06-26-2005, 09:44 AM	#3
Jon STI Driver Location: SE PA Posts: 261 IWSTI Addict since: Jan 2004 Trader Rating: (0)	If anyone's planning on draining their factory-fill gear oil anytime in the near future, I'll be willing to pay the $20 to have it analysed if you'll post the full results here. This is who I use: http://www.blackstone-labs.com/standard_analysis.html

06-26-2005, 06:46 PM	#4
tcam33 Gold Member Car: 05 WRB STi Fav Mod: 1.mod 2.???? 3.profit Location: Edmonton Canada Posts: 245 IWSTI Addict since: Mar 2004 Trader Rating: (0)	I'll send you a sample. Fire me your addy. I'm changing the box's oil soon as well as the rear diff. fwiw the dealer here recommends Motul gear 300

06-26-2005, 07:11 PM	#5
Rev STI Guru Car: 06 V70R Location: Hoffman Estates, IL Posts: 5,544 IWSTI Addict since: Dec 2003 Trader Rating: (0)	Interesting ... When I filled with Motul 75W-90, tranny feel improved a lot. Especially during the winter, I myself didn't like the factory fill so that's my reason for switching it.

06-27-2005, 02:29 PM	#6
CoreySTi04 Junior STI Driver Car: 2004 STi Silver / Silver Fav Mod: XS stealthback Location: South Bend, Indiana Posts: 146 IWSTI Addict since: May 2003 Trader Rating: (0)	Definately let us know what you find out. I switched to Mobil 1 syn 75W-90 and had nothing but problems. The theory around here was that it was actually too slippery to get the syncros up to speed. I was missing shifts like it was my job. Switched to regular Valvoline 80W-90 and no more problem shifting at higher RPM. I never used to miss shifts and now I don't again. I guess the moral of the story is stick with regular oil or play with friction modifiers if you're running synthetic. CoreySTi04

10-25-2005, 09:46 AM	#7
Jon STI Driver Location: SE PA Posts: 261 IWSTI Addict since: Jan 2004 Trader Rating: (0)	Here you go. Thanks to tcam33 for the sample. Interestingly they say it might be a 75W90, but the viscosity is low...

10-26-2005, 07:26 AM	#8
tcam33 Gold Member Car: 05 WRB STi Fav Mod: 1.mod 2.???? 3.profit Location: Edmonton Canada Posts: 245 IWSTI Addict since: Mar 2004 Trader Rating: (0)	Thanks for doing the analysis Interesting comments I expected to see the wear metals a lot higher. FWIW the oil had 9,200mi on it and it was a straight factory fill no additives on my part