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Fuels & Lubricants Discussion all about Fuels & Lubricants. synthetic oil, conventional oil, brands, change intervals, diesel grades, gelling and such debated items like that. Non TDI related postings will be moved or removed. This forum is NOT for the discussion of biodiesel and other alternative fuels.

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Old March 16th, 2006, 09:09   #1
SUNRG
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Default stick with G52 in your tranny - here's why...

If your transmission specifies G52 fluid I highly recommend sticking with it as opposed to changing it out for one of the popular/common replacement manual transmission fluids because the viscosity of G52 is much thinner:
Viscosity Comparison @ 100 C
10.6 = Redline MTL 70-80
13.8 = Amsoil MTG 75-90
15.2 = Motul Gear 300 75-90
15.6 = Redline MT-90 75-90
15.0 = Elf Tranself Synthese FE 75-90
16.7 = Motul MOTYLGEAR 75-90

6.3 = OEM G52 (part numbers G052726A2 / G05272601)
With just over 43,000 miles on my 2004 Golf TDI 5-speed I drained my manual transmission fluid, re-filled with Motul Gear 300, and I brought samples of both the used G52 and new Motul Gear 300 to my local CAT fluid analysis lab.

Since I had written on the G52 oil sample label 75w-90 the lab viscosity tested the sample twice - both times returning a V@100c of 6.4.

My thinking was that either the OEM oil sheared way down OR the OEM fluid started out much lighter than the expected 75w-90.

So, I went to my local dealer this morning, bought a liter of G52, then drove to my local CAT fluid analysis lab and watched as he tested its viscosity right in front of me.

The result: VOA viscosity of G52 = 6.3


OEM G52 did not shear down at all in 43,000 miles of use:
V@100c: New G52=6.3, G52 after 43,000 miles = 6.4
Additionally, in these crazy unseasonably warm temps the Motul Gear 300 shifts fine - but early yesterday morning when temps were in the mid 40s - the first few shifts with Motul Gear 300 were noticably more effortful than the G52 ever was - even at below 0 temps.


Point being that even though Motul Gear 300 has an outstandingly low pour point (flows to -60) - **the 75-90 viscosity of common gear / manual transmission oils is IMO not suitable for use in VW transmissions where G52 is specified.**


OEM G52: 43k UOA




Motul Gear 300: VOA (this is as expected from a 75w-90 oil)
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Last edited by SUNRG; March 16th, 2006 at 09:21.
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Old March 16th, 2006, 09:13   #2
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Cool, thanks for gathering the data...I wish we had the info for G50 which has been used for so many years in these cars. I suspect it's very thin as well.
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Old March 16th, 2006, 09:40   #3
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Quote:
Originally Posted by SUNRG
If your transmission specifies G52 fluid I highly recommend sticking with it as opposed to changing it out for one of the popular/common replacement manual transmission fluids because the viscosity of G52 is much thinner:
Viscosity Comparison @ 100 C
10.6 = Redline MTL 70-80
V@100c: New G52=6.3, G52 after 43,000 miles = 6.4
Interesting! I'd been considering Redline MTL...I'm wondering, though, in light of G52's lower viscosity, why fuel economy seems to improve when one switches to MTL?

Mike
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Old March 16th, 2006, 11:04   #4
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Quote:
Originally Posted by Mike_M
Interesting! I'd been considering Redline MTL...I'm wondering, though, in light of G52's lower viscosity, why fuel economy seems to improve when one switches to MTL?

Mike
i think that phenomena has primarily been observed in earlier TDIs - not the 2004+ tranny's specifying G52.

G50 and G51 are listed by Bentley as 75w-90, whereas after G52, on page 34-15 in my Bentley book, it states "Viscosity is not specified for either (G52) gear oil."

therefore, while G50 may be on the light side of the 75w-90, G52 is significantly lighter - no where near 75w-90.

cheers!
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Old March 16th, 2006, 12:02   #5
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Quote:
Originally Posted by SUNRG
i think that phenomena has primarily been observed in earlier TDIs - not the 2004+ tranny's specifying G52.

G50 and G51 are listed by Bentley as 75w-90, whereas after G52, on page 34-15 in my Bentley book, it states "Viscosity is not specified for either (G52) gear oil."

therefore, while G50 may be on the light side of the 75w-90, G52 is significantly lighter - no where near 75w-90.

cheers!
Ah...my apologies. I didn't know which tranny fluid was specified for which models (didn't check). Didn't know G52 was PDs only. Mine's a 2002 (non-PD), hence MTL is still an option?

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Old March 16th, 2006, 12:17   #6
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I am pretty sure G52 is 75W per info from VW-AG. It's also dino-based oil.

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Old March 16th, 2006, 19:11   #7
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with gear oils, the acceptable V@100c range of 75w-90 fluids is 13.5 to 23.9 (the beginning of the 140 range). however, the only number that really matters for this discussion is the 13.5 lower cSt limit for 75w-90 fluids.

i realize we don't ultra-analyze gear oils like we have motor oils, so to put this in SAE terms all the common 75w-90 fluids would be 40 weight motor oils (cSt range = 12.5 to 16.2).

the cSt range of 30 weight oils is 9.3 to 12.4, which G52 is well below...

the cSt range of 20 weight oils is 5.6 to 9.3, so with a VOA cSt of 6.3, G52 would barely qualify as a 20 weight motor oil.

while technically a light 20 weight - the CAT fluids analysis lab manager said he thinks G52 is a 10 weight, as does Blackstone Labs [check out this BITOG thread - link].

DDs link states "G52: Manual gearbox oil SAE 75W based on a conventional hydrocarbons." and this fits since in gear oils 75w (straight 75 or 75 being the upper number) cSt range is approximately 4.3 to 7.2 cSt.
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Old March 16th, 2006, 19:33   #8
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Quote:
Originally Posted by Mike_M
Ah...my apologies. I didn't know which tranny fluid was specified for which models (didn't check). Didn't know G52 was PDs only. Mine's a 2002 (non-PD), hence MTL is still an option?

Mike
yeah u could use MTL... i wonder if anyone has tried G52 in a pre-2004 VW?
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Old March 16th, 2006, 19:36   #9
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There is a synthetic G52 and a non synthetic G52. Which one did you have? Was it the one in the white bottle?
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Old March 16th, 2006, 19:37   #10
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good to know! my stock fluid is gettin notchy. I loved MTL, it was the only fluid that wouldnt make my 90 suzuki sidekick grind into 2nd gear, and it wasnt impossible to get into gear on a cold morning!

G52 here i come, in an 04 PD
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Old March 16th, 2006, 19:39   #11
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I have G52 in my 2000 Jetta from the white plastic 1L bottle. And my tranny is rediculous notchy when it gets cold outside.
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Old March 16th, 2006, 20:51   #12
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Quote:
Originally Posted by OdinsRageSS
good to know! my stock fluid is gettin notchy. I loved MTL, it was the only fluid that wouldnt make my 90 suzuki sidekick grind into 2nd gear, and it wasnt impossible to get into gear on a cold morning!

G52 here i come, in an 04 PD
FWIW - i recently ordered an Air Lift kit from Summit Racing and they gave me a $20 credit toward my next order - but i couldn't find anything else they carried that i wanted until...

i realized they carry Redline MTL. so i basically ordered and will receive a couple liters for free. i'm going to put it in just to see how it feels. as a 70w-80 MTL is the closest of the "popular TDI club aftermarket gear lubes" to G52 in viscosity...

i'll report back soon.

cheers!
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Old March 16th, 2006, 21:01   #13
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Quote:
Originally Posted by SUNRG
yeah u could use MTL... i wonder if anyone has tried G52 in a pre-2004 VW?
Cool...thanks again. And good question...I wonder if anyone who has will read that and answer?

Mike
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Old March 16th, 2006, 21:20   #14
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Mike, you could by chance look up 2 posts....
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Old March 16th, 2006, 21:34   #15
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Wow, 6.3 cst! But then, if its a straight 75, it would thicken up a lot with lower temps and be notchy like david_594 experiences.

People were saying watch out with the pennzoil (aka GM) synchromesh. That has a visc at 100C of 9.08 cst. I don't get why VW went so thin. BTW, the 40C reading is probably more pertinent to normal driving as the tranny probably doesn't get so hot. Pennzoil synchromesh is 41.6cst @ 40C.
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