# selecting manual transmission fluid



## dtbaker (Jan 5, 2008)

does anyone have info on various synthetic manual trans fluids... looking to maximize efficiency? I need to replace fluid anyway, and might as well use a good one.


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## rich18325 (Aug 17, 2008)

Hi. You didn't note what car you are working with. You need to check your owner's manual. Some cars use ATF in their manual transmission or it will specify a trans fluid of a certain viscosity. you can get this info from the web also. Once you have determined what is required, AMS Oil ( a brand name) has shown to be a good choice in my experience. Good luck Rich


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## dtbaker (Jan 5, 2008)

rich18325 said:


> Hi. You didn't note what car you are working with. You need to check your owner's manual. ...AMS Oil ... a good choice in my experience. Good luck Rich


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thanks! Donor transmission is a 1997 Suzuki swift (Geo Metro/Pontiac Firefly). I took a look in owners manual, and it says to use: gl4 75w90 gear oil . which is pretty darn thick stuff!

Dan
envirokarma.org/ev


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## TX_Dj (Jul 25, 2008)

Dan,

I have to agree with Rich. Check Amsoil's site for dealers near you. The strange thing about Amsoil though is that they do not sell through retail outlets, only private dealers (sort of like Amway, which I always wondered if there was a relationship there).

Amsoil makes some of the best oils on the market today imho. Over the years I've read many white papers about studies done on their oils, and the one that sticks out in my mind goes something like this: Brand new heavy dump truck. First fluid fill included amsoil in all places it takes oil, and amsoil micron filters. Following the default 12,000 mile service interval, the filter was switched for another amsoil filter, a sample of the oil was taken for analysis, and it was topped up as appropriate. Notice I didn't say they changed the oil. The analysis came back clean, all items still within spec. This routine continued for over 400,000 miles of heavy work, and every 12,000 miles the oil analysis came back perfect. Still running on the original engine/transmission/differential parts. Now, that's not uncommon for big diesels to run forever so long as routine maintenance is performed- but it is uncommon for them to go 400,000 miles without a full oil change and still show good on analysis. Very economical to run amsoil in a situation like that, where the engine contains gallons of oil and needs service every 12,000 miles.

Using that knowledge, my uncle began using amsoil in everything on his ranch. When he bought his new truck (almost a decade ago) he put amsoil in it from the start, using their special filters. He doesn't bother with the oil analysis, he just changes the filters and tops off the oil every 6000 miles. He's running a late 90's-ish Ford F350 Powerstroke with well over 300,000 miles on it now and has never had to worry about the thing. He does all the regular maintenance EXCEPT change the oil.

According to amsoil, this has most to do with their filters, but a lot to do with their oil as well.

I don't use amsoil, just because I don't want to become a dealer or go to someone's house to buy oil.  I tend to use Red Line, Royal Purple, and Mobil 1. They are all fairly similarly priced, with Mobil 1 being the cheapest.

Now, none of that helps with your original question...

If the manufacturer says you need 75w90 GL4, you should probably stick with that. I have heard of people using 10w30 (even manufacturers) in gearboxes, and most new vehicles will even use ATF for their manual fluids. But if yours is recommending GL4, you should likely stick with that. I don't want to make a recommendation for you and have it destroy your gearbox. 

Perhaps you could get a solid answer from the prof of automotive engineering at a nearby college/university?


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## dtbaker (Jan 5, 2008)

cool... I remember testing Amsoil in conveyor gearboxes years ago; it outperformed everything else for what we were testing... I poked around the web a little and found a direct sale site at

http://www.amsoil.com/storefront/svo.aspx


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## ragee (May 25, 2008)

I bought my Amsoil at Carquest our local autoparts store and it is designed for 75-90. Works fine in my Ford Ranger EV.


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## Thaniel (May 25, 2008)

I have used redline before in an ICE car. http://www.redlineoil.com/products_gearlubricants.asp

They have various weights. The main thing I noticed was it did not seem to thicken as much at lower temps as standard gear oil. I'd use it again expecially if in a colder climate.


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## etischer (Jun 16, 2008)

I've had good success with Redline oils. Their oils are much thinner viscosity at room temperature than other equivalent weighted oils, and they are full synthetic. 

Make sure you use the Redline MTL fluid, and not the Redline gear oil. You need some friction to make the synchros work, if you use straight gear oil you might get grinding gears because the oil reduces the friction too much.


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## Schmism (Aug 16, 2008)

Redline or royal purple both are good synthetic fluids.


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## AndyH (Jun 15, 2008)

Schmism said:


> Redline or royal purple both are good synthetic fluids.


Redline, AMSOIL, and Mobil 1 are the ONLY 'synthetics' that are PAO or ester-based man-made synthetics. Royal Purple is not...and has been trashed for false advertizing.

http://www.imakenews.com/lng/e_article001398592.cfm?x=b11,0,w

April 8 2009

"Royal Purple Ltd. was black and blue after BP Lubricants USA took it to task over advertising claims for its synthetic motor oil, finding a receptive audience in the advertising industry’s self-regulatory forum...
<snip>

...NAD recommended that Royal Purple discontinue claims that stated, “Improves fuel economy by as much as 5 percent” and “Fuel economy improvement up to 5 percent or more” because its Environmental Protection Agency testing was inconclusive and the “Oklahoma State Study” and single cylinder Labeco CLR diesel engine testing cited in Royal Purple’s advertising was not relevant. The NAD noted the 1997 OSU Study was “outdated and nothing in the record demonstrated that the formulations of the competitors’ oils were similar to those available for sale on the market today.”


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## electric85 (Apr 10, 2008)

i'd go with Lucas trans treatment with whatever fluid you choose...that stuff is great and you can get it at any NAPA store.


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## AndyH (Jun 15, 2008)

dtbaker said:


> does anyone have info on various synthetic manual trans fluids... looking to maximize efficiency? ...


I pulled this together for a VW TDI forum. Last update was Oct '07. Most data comes from manufacturer spec sheets, but has been validated and/or expanded with oil analysis. Sorry...it's heavily weighted to Euro and VW fluids.

There's been a steady shift from 80-90 gear lubes to fluids that are basically the viscosity of automatic transmission fluid. The viscosity drop in gear oil (and engine oils) is to help automakers squeek out another 1/4 of 1% of corporate average fuel economy...primarily so manufacturers can sell more trucks...

When it comes to improving fuel economy thru changing fluids, the differential is the largest factor, with tranny second and engine last.

Changing from petroleum to synthetic - even with the same viscosity - can make a significant difference. For example - a class 8 truck (semi) tractor with dual drive axles, when moving from petroleum fluids to real synthetics, can gain 8.3%. 5.25% is the differentials, about .5% is the engine.

I did some highway testing with my old VW diesel (calibrated ScanGuage, GPS, full tanks from the same pump at the same times of day) - moving from the factory 75W-90 synthetic, to a synthetic synchromesh fluid, down to VW G52, and back up. The move from 75W-90 to the really thin G52 was worth 1.8mpg. In the end I moved back to 75W-90 to keep my 390,000 mile transmission a bit happier.

VI is viscosity index and speaks to viscosity stability as temperatures change. Higher is more resistant to change with temperature.

Transmission fluid viscosity is normally rated at 40C, while engine oils are rated at 100C/212F.

The viscosity scales for gear oil and engine oils are different - a 75W-90 gear lube is similar to 10W-40 engine oil. Synchromesh is in the 5W-30 range, and G52/Mercon SP/Dexron VI is about a 0W-10 engine oil.

Viscosities are in cSt - centistokes - and are essentially a timed flow thru a cup with a hole in it. One can normally move one viscosity grade higher or lower than designed and maintain general performance and protection.

(Manual Tranny Fluids)

VI [email protected] [email protected]
128 159.0 18.3 = AMSOIL CTL SAE 50 Powershift GL-1
..............16.7 = Motul MOTYLGEAR 75-90 GL-4/-5
..............15.6 = VW G50/G51 GL-4
185 90.0 15.6 = Redline MT-90 75-90 GL-4
..............15.2 = Mobil 1 Synthetic 75W-90 GL-5
..............15.2 = Motul Gear 300 75-90 GL-4/-5
..............15.0 = Elf Tranself Synthese FE 75-90 GL-4/-5
132 116.0 14.9 = AMSOIL AGL 80W-90 GL-5
177 84.5 14.7 = AMSOIL MTG 75-90 GL-4
..... 76.6 14.2 = VW G052-911
133 76.2 11.0 = AMSOIL CTJ SAE 30 Powershift GL-1
183 56.2 10.6 = Redline MTL 70-80 GL-4
194 47.1 9.6 = AMSOIL MTF Synchromesh Trans fluid (GM/Chrysler) GL-?
208 41.6 9.1 = Penzoil Synchromesh trans fluid GL-?
198 34.0 7.5 = Redline D4 ATF Dexron III / Mercon / API GL-4
138 40.5 7.1 = AMSOIL CTG SAE 10W Powershift GL-1
..... 31.2 6.5 = VW G-052-171-A2 GL-?
..... 35.1 6.4 = VW G-055-726-A2 GL-?
..............6.3 = VW G52 (part numbers G052726A2 / G05272601) GL-?

(Automatic Tranny Fluids - except for Redline D4 dual-use)

VI [email protected] [email protected]
.............8.3 = Honda CVT Fluid
.............7.6 = Mobil 1 Synthetic ATF

198 33.5 7.5 = Redline D4 ATF Dexron III / Mercon / API GL-4
.............7.4 = Mobil 1 Synthetic Dexron/Mercon
197 32.5 7.2 = Redline Synthetic ATF Dexron II / Mercon
.............7.1 = Mobil 1 Synthetic Multi-vehicle ATF
138 40.5 7.1 = AMSOIL Ford type F auto trans fluid
168 37.4 6.8 = AMSOIL Automatic Transmission Fluid ATF 
..........5.5-6 = Ford Mercon SP

There are three basic categories of base oil on the streets. Group I and II are refined petroleum. Group III is refined petroleum that has also been dewaxed (improves low-temp performance) and high-pressure hydrogen processed to improve high temperature performance. Group III can be called 'synthetic' (legal definition) in the Americas but no where else in the world. Group IV is man-made synthetic base oil - PAO. Group V is an 'all others' group and contains petroleum and synthetic products - from Vaseline petroleum jelly to the man-made esters used as a component in lubricating oils.

Most of the products on the North American market - the 'synthetics' and 'synthetic blends' are made with Group III base stock. All of AMSOIL's products (with the exception of the XL products) is Group IV/PAO based. RedLine products are primarily ester based. (Both companies use a combination of PAO and ester.). Mobil 1 products are primarily PAO-based, but some also contain some amount of Group III (legally synthetic, but technically a synthetic blend because of the petroleum-derived content.)

Gear teeth are kept apart by a combination of fluid viscosity and the extreme pressure components in the oil's formula. Moving to a lower viscosity product can increase efficiency but can also result in increased wear rates. As viscosity thins, the anti-wear additives must be improved to maintain the same low wear rates. Keeping wear in check is important because it's a geometric progression - one piece of steel or grain of sand in a gear box can scrape a pair of pieces from two gear teeth. The three pieces can generate a new 6 pieces, the current 9 pieces can generate 18...and away we go.

It's best to match both the viscosity and the performance rating (such as GL-4) when selecting a replacement fluid.

If the transmission is filled with 75W-90 GL-4 petroleum, move to 75W-90 synthetic (AMSOIL, Redline, Mobil 1, or a European product) that also has the GL-4 (or similar OEM rating). Next move might be to something in the Synchromesh arena.

Driver technique and aerodynamics are better first targets - efficiency gains from lighter lubes are measurable but small, and if taken too far can lead to unhappy synchronizers and/or increased wear. 

Please do not add anything to any finished lubricating oil - including transmission, engine, or differential. At best you're only out a bit of money. At worst one can lose their component warranty, oil warranty, have bearing wear and/or increased rust/corrosion. Lubricating oils are designed and tested specifically for the intended application - don't upset the sensitive chemical balance.

Andy

'97 VW Passat TDI wagon 391,000 miles
AMSOIL Jobber
Rechargeable Lithium Power


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