Effect of gear oil viscosity on transmission efficiency (Metroid owners take note)
 

This post is really about 2 things:

1. Specifically, I believe the transmission oil weight called for in the Suzukiclone owner's manual is incorrect, and
2. An experiment that starkly illustrates the magnitude of energy losses in a manual transmission comparing "thick" vs. "thin" oils.

If you don't have a Suzukiclone, just skip Part 1 and scroll down to Part 2 for the interesting viscosity comparison results.


https://www.austinev.org/evalbum/imgm...pg&w=300&h=225

Part 1.
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Why I believe the Suzukiclone owner's manual recommended transmission oil weight is wrong

An acquaintance in British Columbia converted a 1987 Suzuki Forsa to electric drive, and was concerned that he was seeing a lot of energy loss in the drivetrain (based on the amount of energy required to spin the wheels on jack stands).

He mentioned to me that he was thinking of going to synthetic oil in the transaxle, and I told him I believe the specification in the owner's manual (calling for 75w90 gear oil) is incorrect.

I came to this conclusion after having changed the transmission oil in my own 2 Suzukiclones. The first one I changed to 75w90 synthetic soon after buying it. I noticed afterward (but wasn't certian) that it seemed to increase the amount of "grinding" of synchros in quick gear changes - a common complaint about the transmissions in these cars.

When I got Firefly #2 (the Blackfly) with just 2,000 km on the odometer, I also thought I should change its transmission oil, because it sat parked for 7 years. But when I did this, I was careful to pay much closer attention to the viscosity of the fluid I drained from it - and I saw that it was obviously MUCH thinner than the 75w90 oil called for in the owner's manual. Note this was unquestionably the factory original tranny oil that was drained from the car.

A bit of investigation on teamswift.net uncovered several people recommending GM's AC Delco Synchromesh brand of semi-synthetic manual transmission oil (it doesn't have a viscosity/weight listed on the packaging). I bought some, but before pouring it in the car, I did a few tests to compare the various viscositis of the oils I had:

• I did a simple timed "pour test" of a measured amount through a cotton filter, and saw that the AC Delco Synchromesh lube was actually closest to 5w30 engine oil in viscosity (based on the time to drain a measured amount through the filter).
  .
• I also pour tested the factory original oil that I drained from the Blackfly (Firefly #2). It also poured through the filter at the same rate as the Synchromesh oil and 5w30 engine oil. Hmm!

This told me that the manual-recommended 75w90 synth oil I put in Firefly #1 was too heavy. Fortunately, I owned both cars simultaneously for a couple of weeks after getting the Blackfly (before selling #1). So I was able to do another test:

• my next test was to drain the 75w90 synth oil from Firefly #1 and replace it with the "old", thinner, factory original oil I drained from Firefly #2.
  .
• After doing this, the amount of "synchro grinding" immediately reduced.

So I returned the 75w90 synthetic gear oil I had bought for Firefly #2 to the store, and instead added the GM Synchromesh oil to that car. I have had almost no trouble with its synchros since then. I also "moved" that fluid from the original transmission to the used "taller" transmission I installed later on. Still little synchro trouble to speak of, even though the used transmission has 160,000 more km on it than the car I put it in.

From all of this, I came to the conclusion that the 75w90 recommendation in the owners manual is incorrect. It's too heavy.

Part 2
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An experiment comparing energy losses from "thick" vs. "thin" transmission oils

Written by Roger - electric Forsa owner.
https://tech.groups.yahoo.com/group/ev/message/35167
Apr 12, 2007

RE: Sprint/Metro Drivetrain losses

I had written:

> The tranny is full of fresh 75W90 gear oil, per the manual,
> however, I've been advised that the manual is wrong and a GM
> semi-synthetic lube is what should be in there. I'm
> skeptical that the lube alone could be responsible for this
> sort of loss, but since an oil change is easier than
> rebuilding the tranny, I'll try that first ;^>

As it turns out, it seems (from checking a partial bottle remaining in
the garage) that the tranny is actually full of 80W90, not 75W90 as I
originally wrote.

I put the car on stands again (under the frame with the suspension at
full droop since the suspension angle didn't seem to affect energy
consumption in my earlier tests and I feel better with the stands under
the frame when I'm going to be getting under the car).

All following energy consumption observations are based on battery pack
voltage and current as reported by my E-Meter.

I spun the wheels in 2nd for a few minutes to warm things up first, then
measured energy use in each gear at 40kph (except 1st, which was
measured at 30kph):

5th 23.4A @ 123.5V (116.3Wh/mi or 72.2Wh/km)
4th 22.9A @ 123.0V (113.4Wh/mi or 70.4Wh/km)
3rd 25.5A @ 123.0V (126.2Wh/mi or 78.4Wh/km)
2nd 30.8A @ 121.5V (150.6Wh/mi or 93.6Wh/km)
1st 37.5A @ 121.5V (244.5Wh/mi or 151.9Wh/km)

After draining the old fluid, I poured in a half litre or so of Varsol
and spun the wheels for a minute or two to flush things out:

2nd 22.5A @ 123.0V (111.4Wh/mi or 69.2Wh/km)

This was then drained, and the tranny filled with 2.5 litres of the
recommended AC Delco Synchromesh fluid (p/n 89021808, IIRC):

5th 16.1A @ 123.0V (42kph, 75.9Wh/mi or 47.2Wh/km) (34.7% lower)
4th 17.0A @ 122.5V (42kph, 79.8Wh/mi or 49.6Wh/km) (29.6% lower)
3rd 19.7A @ 120.0V (42.5-43kph, 89.6Wh/mi or 55.6Wh/km) (29.0% lower)
2nd 22.4A @ 120.0V (39.5-40kph, 108.2Wh/mi or 67.2Wh/km) (28.9% lower)
1st 37.7A @ 118.0V (39kph, 183.7Wh/mi or 114.1Wh/km) (24.9% lower)

So, going to the [GM Synchrmesh] fluid definitely seems like a step in the
right direction, however, not nearly as large a step as is required :(

On the plus side, the 3rd-2nd downshift "crunch" is gone, which had been
one of the touted benefits of using this tranny fluid.

So, some progress, but the hunt for better efficiency continues...

Cheers,

Roger.

---

Just a note: the energy savings seen from the less viscous gear oil doesn't translate directly to an equal decrease in total fuel consumption (or electricity use, in this case). Only the energy difference required to spin the wheels on jack stands was measured - not the total difference to actually drive the vehicle (with all its other associated losses factored in).

When I drained mine to change an axle shaft I noticed how thin it was. It was immediatly apparent that this wasn't normal gear lube. That is a cool test showing energy loss. I'm really glad I refilled with new synchromesh after seeing that :) .

Not a Metro but...
Saturn S-series cars, manual and automatic, use Dexron III ATF in their transmissions. ATF is like water, compared to even 5w30 motor oil. Over the winter I experienced several instances of 1st to 2nd gear grinds when the temp was in the single digits. I had to double-clutch into 2nd to avoid gear grinds. After the first couple of 2nd gear DC shifts, DC was no longer required. Even ATF thickens in <10F. Now that I've got new ATF replacing the old, 56k-mile ATF (Saturn recommends changing it every 30k), I'll see how it shifts next February. The new ATF was noticeably lighter in color than what was drained out. Looked like the original owner didn't change it in the 44k miles they had the car.

Good info. When I switched to synthetic transaxle lube on my 626, I had fits trying to figure out whether I should use the gear lube kind or the ATF kind (some Mazdas had ATF in the manual transaxle). Someday I will switch my Element over...

Neat writeup!

The Porsche 914 manual gearbox calls for 80W90 gear oil - so I know that it's not absolutely unheard of for crash boxes to run this high of a weight.

As an aside, when I got my first Civic, the manual tranny was noisy and shifted weird sometimes, so I decided to change the fluid. When I removed the drain bolt, dark greyish-red fluid that was thin poured out. The previous owner had filled it with ATF!

Assume nothing. I've know a few standard trannies that were spec'd for auto tranny fluid. I think we had a standard trans once that was spec'd for motor oil, too! Same stuff that went into the motor. Also power steering systems spec'd for auto tranny fluid.

This makes me interested to try thinner gearbox oil in my car at some point!

I once had a Rover Metro (a small car like a Suzuki Swift), automatic.

It didn't have automatic transmission fluid - it just used standard engine oil!

In fact, it shared the oil with the engine :eek: So you had to keep it topped up carefully and change it twice as often as usual - if you let the engine oil get old, your transmission would get damaged!

I use 10W-30 engine oil in my Honda transmissions.

That is a huge difference!

i would in my cars btu they gotta last, one of em i could change it to somehting lighter, but the other i dont wanna run the risk of killing the tranny...

The manual tranny in my Cortina is worn. It was becoming very difficult to shift into 2nd gear when starting out, needing a lot of force on the gearshift, even when not particularly cold outside. We changed the 80w90 it had for ATF. Couldn't say how much that helped FE, but that made 2nd gear much easier to shift into. The tranny has been working fine with ATF for a few years now.

Great experiment :)

I know of at least one person over on mazda626.net that uses ATF in his gearbox.... He is in a cold region though :)

Not sure what I'm going to do for gear oil in my Jetta just yet... I might just bite the bullet and get the factory stuff... I haven't heard of any problems with it, other than the high price -- ~$20 per 500mL bottle and there's 2.1L in the gearbox!

For trans that use ATF might try Mobil 1 synth ATF with Lubegard ATF additive.

Synth ATF is probably less viscous in cold temps...the additive reduces drag when hot.

For trans that use gear oil...use a moly additive?

https://www.molyslip.com/Testimonials...arms_Jan94.pdf

Look for the best moly prices...some is way expensive. Other additives like Militec also work.

Every honda I looked at with a manual said to use 10W 30 in it, or the honda labled manual trasmition fluid, right now I have the 5W 30 Amsoil MTF that is labled as working for hondas, I think the same stuff is in my moms Metro tranny, and seems to be working great.
last summer I ended up switching back to 10W 30 in my tranny, because at around 228,000 miles the main bearing went out on it, and the thicker oil quited it down long enough for me to drive 1,000 miles home, thicker fluid does provide more cushin, so I wouldn't switch something that calls for 75w 90 over to 0w 20

Yep, my CRX is also speced the same way!

In my case, after doing my research online, I went with the (synthetic) Red Line MTL 70w80 (my research suggested that Red Line made the best product for manual transmissions, whereas Amsoil had a better product for automatic transmissions). The Red Line MTL is actually thinner than the motor oil it replaces (and also rated specifically as a fluid that should save some gas), but still seems to do a good job at keeping everything lubed up (and cooled down) in the transmission. And honestly, it's amazing how smoothly (and easily) that car shifts now (with that Red Line fluid in its transmission)!

NOTE: The 70w80 rating is the "gear oil" rating, which doesn't have the same number scale as the motor oil rating. In fact that 70w80 is actually a little thinner than the 10w30 motor oil my transmission is rated for. Furthermore, the Red Line product is actually rated as being a good "direct replacement" for the fluid in any manual transmission (for example, my CRX) that was originally speced for 10w30 motor oil...

FWIW:
I did use the Amsoil's fully synthetic AFT for my wife's (auto-transmission) Civic, as well as our (diesel) Ford pickup's transmission. And both transmissions seemed to very much like the Amsoil "universal" synthetic ATF fluid.

BTW:
I'm now an Amsoil dealer, in case anyone (who isn't a current Amsoil customer of another dealer) is interested in any of their products. So if any of you want to try their products (and I do think some of their products, such as good synthetic oils and transmission fluids, can help some with FE), I'd be happy to offer gassaver members discounts. Just PM me if you are interested.

NOTE:
Amsoil dealer rules prevent me from selling to (or even offering discounts to) existing Amsoil customers (of a different dealer). So much as I would love to extend that offer of gassaver specials to all gassaver members, I really am only allowed to extend that offer to gassaver members that aren't current/existing Amsoil customers...

Oil viscosity in Geo Metros
 

I remember reading in a tech manual that not all Geo Metros use the same transmission fluid in their manual transmissions. The book recommended checking the fluid you remove from the transmission to know which one to use. I also remember something about some Geo Metros being produced in Canada and some being produced in Japan. Perhaps one could tell which fluid to use based on where it was produced. I remember a salesman telling me that new Metros sold on the East side of the Mississippi river (in the U.S.) where made in Canada and the ones sold on the west side where made in Japan. I don't know how true this is. My first and Second Metros (92 Xfi, 94 base) where first sold on the east side of the Mississippi and where made in Canada. I remember being surprised at how thin the fluid was in both transmissions.

Thanks for the extra info - that's interesting about the manual recommendation - pretty much what I did for my car.

The EV owner who gathered the info I posted at the top of this thread is driving a first gen Suzukiclone, so I'm sure his was made in Japan. Mine was built in Ontario.

redline MTL is a suitable replacement for syncromesh, in my experience.
regular gear oils dont have the friction modifiers to improve the syncro action like one of the specialty manual tranny fluids
penzoil actually makes gm syncrmesh and it's cheaper in the yellow bottle from a regular parts store

also note than on many manual transmissions GL4 gear oil is specified, if a GL4 is spec'd DO NOT put a GL5 gearlube in place of it. GL5 does not fully supercede GL4 in all applications as it contains additives that may be corossive to yellow metals (such the the bronze parts in many syncronizer assemblies)

as far as engine oil in a trans.. minis used shared oil, and saab at least used to spec 5w30 engine oil in their manual trannies. With a note saying do NOT under any circumstances use a synthetic motor oil.

My nissan will be getting redline MT90 (the heavy weight version of MTL) in the near future as it calls for a 75w90

Jeff

MTL oils
 

I run 70w80 in my swift and think it is the best oil I have run to date...
Shifting is smooth , cold weather operation is outstanding what can I say
No.1 oil in my books...

Being in the process of rebuilding the transmission in the Jeep, I've done some research on this topic recently.

Contrary to popular belief, gear oil is not rated on the same scale as motor oil. "75 weight gear oil is actually about the same viscosity as 10 weight motor oil." ( https://www.calsci.com/motorcycleinfo/Oils1.html ). The reason motor oil is not normally used is due to the detergents and other chemicals that may be present in it. My Jeep transmission requires an oil that does not contain sulfur as it wears the 'yellow' metals quicker.

This leads me to an interesting fact. The Jeep owner's manual specifically calls for a GL-5 or equivalent gear oil. Most GL-5 oils contain sulfur. However, most GL-3 oils do not (possibly all of them). So misinformation from OEM can happen.

Yes, some transmissions (such as those in Saturns) call for ATF. The fact of the matter is that manual transmissions, although very similar in design, contain different tolerances and materials. As far as how thin the oil is when you drain it, had you just run the car? Transmissions don't get nearly as hot as engines, but they do heat up. As with most any liquid, viscosity changes with temperature.

From what I've read, for any transmission requiring gear oil (not ATF or possibly the honda trannies), Redline is one of the highest quality oils you can buy. It's just what Redline does and it's what they're good at. Personally, I will be using Penzoil Synchromesh in the Jeep trans.

The final verdict will probably come with time and a bit of trial and error, but I hope I cleared a few things up.

Matt

I have a 99 Metro, which transmission oil should I be using? The GM Synchromesh?

Also, how do I drain the fluid already in there?

Sorry for the noob questions.