voltamps
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Re: How To: Reduction Gear Oil Change

Thu Apr 15, 2021 8:25 am

knightmb wrote:
Wed Apr 14, 2021 7:36 pm
I suspect that the good numbers I'm seeing are only because I am driving under 55 MPH up and down hills.
Tough to measure exactly, because variables have to be the same except for the gearbox oil used.
Wind, tire pressure, temperature, weight in car, are the major things that affect efficiency.

One thing I might try is to drive to a suitable hill, without interfering traffic near me, and do a "Coast Down Measurement" in Neutral, to see how far it coasts. Then change the gearbox oil and try it again to see the difference. Then, we'd know what energy efficiency gains we have.

About those Coast Down tests, I do know a fellow at NREL (a place that does EV research) who knows somebody at INL (Idaho federal lab like NREL) that does more of those coast down tests than NREL does. I'll ask them if they know what gains can be had with thinner gear oil. ( In nerdy engineer-speak, I'll ask them what the partial derivative of Range is with respect to gearbox oil KV100 in the Leafs they've tested before. )

Image
https://www.energy.gov/sites/prod/files ... 2015_o.pdf
They have tested all kinds of EVs in Idaho in the last 12 years. Your taxpayer dollars at work.

In ICE vehicles, for comparison, the use of lower-viscosity engine oil has been studied a lot for increased MPG. It's commonly known that you gain about 1.5% fuel efficiency when you use a 0w-20 (kv100 8) oil instead of a 5w-30 (kv100 11) oil. That's a "partial derivative" of delta 1.5/3 = 0.5%/kv100
knightmb wrote:
Wed Apr 14, 2021 7:36 pm
As you mentioned though, maybe there is a minimum viscosity needed to protect the gears so they can continue to sling the lubricate around freely and properly along with the chemical changes over time from the gears crushing the oil.
If you go too thin, then you lose too much hydrodynamic oil film thickness, placing excessive burden on the EP (extreme pressure) chemical additives in the ATF oil here, resulting in more boundary (metal-to-metal) friction, increasing overall friction even though hydrodynamic friction goes down. (For a deep-dive, google a Stribeck Curve image, and see the lowest point on that curve is where the hydrodynamic drag is lowest right before the metals touch.)
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Re: How To: Reduction Gear Oil Change

Thu Apr 15, 2021 9:47 am

Tribology is a huge topic... I only did the bare minimum in college :lol:

Thanks for the links, was very interesting to read!
voltamps wrote:
Thu Apr 15, 2021 8:25 am
............
(For a deep-dive, google a Stribeck Curve image, and see the lowest point on that curve is where the hydrodynamic drag is lowest right before the metals touch.)
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Re: How To: Reduction Gear Oil Change

Thu Apr 15, 2021 10:07 am

Finally got a 70 MPH comparison, interstate driving between two cities, lots of rolling hills to drive up and down, though at that speed, not much is gained for regen unless it is a tall hill. Since everyone else is always doing +90 MPH, it's easy not to get stuck behind anyone, :lol:
Just the first reading today, hopefully will have more to compare in the future, the smallest increase I've seen so far, but given the speed and wind resistance, it makes sense.

Route 6 - All of these in April, weather sunny and pleasant, little to no wind...
25.1 miles 3.6 miles/kWh
25.1 miles 3.6 miles/kWh
25.1 miles 3.6 miles/kWh
25.1 miles 3.6 miles/kWh
25.1 miles 3.9 miles/kWh <- Gear Oil Change
knightmb wrote:
Wed Apr 14, 2021 11:57 am
Just some recent numbers, sorry about the rough format, trying to copy/paste from the Nissan website and put into a spreadsheet isn't that easy and then trying to paste it here in a readable format without requiring an external link. The lbs are CO2, just was easier to leave it in than trying to edit it all out. :mrgreen:

April 2021 (basically, the same driving route during the month, weather has been fairly consistent here, no AC/Heat needed)
These below never have any speeds greater than 55 MPH, but is the same distance driving to and from the same start and end place, even the times are consistent day to day.
.................
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Re: How To: Reduction Gear Oil Change

Sun Apr 18, 2021 6:52 am

Even the vehicle knows something up. I've never seen the guess of meter, well guess so high before :lol:
This is the SL Plus, so it has less range than the other trims because of the additional weight (vs. S, SV) This Leaf only has an EPA range of 215 miles. I put that to a test with an "uphill the entire way" drive from Franklin to Knoxville (total trip was 201 miles), I finished the trip with 23 miles to spare (getting 3.6 miles / kilowatt hour, so I used that to calculate remaining mileage from what LeafSpy showed remaining capacity) All the range test for the 2020 I've read or watched videos on seem to conclude that is impossible, so the only variable is this gear oil change. Either I've got the luckiest setup for weather driving (must have tail wind on all my trips?) or there is something to putting ULV in. I'm still waiting on my results from Blackstone Laboratories to tell me how my "old" gear oil performs. I'll be sure to post that up here too when I get it.
All of this is anecdotal evidence, so even I am skeptical of giving to much credit to the ULV until I have more data.

Image
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Re: How To: Reduction Gear Oil Change

Mon Apr 19, 2021 7:24 am

knightmb wrote:
Sun Apr 18, 2021 6:52 am
........ "uphill the entire way" drive from Franklin to Knoxville .....
That is "EV Central Country". Smyrna, Chattanooga, etc., I continue to read about more EV or battery factories there!! Do you get tours? Go to SAE Meetings in the area for cool meetings? That's car-country after all. Like Michigan with southern accents.

About the use of Valvoline ULV, there r a couple of graphs that might explain it all better (pic is worth 1k words....):

Image

That's for an ICE engine, yet similar things happen in a transmission, where viscous drag friction works against energy efficiency but you get lower metal wear.
Similar shape to our comparable graph for a Leaf gear reduction unit anyway.

(HTHS is just another type of viscosity, measured at very hot and fast (high speed shear) conditions, so it's like our KV100 baseline fluid property sufficiently enough.)

All that out of the way, if the Valvoline ULV (lower viscosity over all temperature ranges than Nissan Matic S) is causing the Gear Reduction Unit to operate at it's minimum friction (greatest range point), then some additional wear can be expected, over using Matic S or Redline D6 or Amsoil SS, any higher-visc ATF fluild. Notiice on the wear graph there really isn't much difference in wear, something around 10% extra wear from getting max Range here.

On the graphs above, if you're getting a Range Increase from Valvoline ULV, then you may be at the HTHS viscosity-equivalent point of 2.5 on the graph, .... If there, then a 10% or so increase in wear rate happens, compared to people running thicker ATF fluids who might be at the HTHS 3.1 point on the graphs, more hydrodynamic (viscous losses) but slightly lower wear too.
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Re: How To: Reduction Gear Oil Change

Mon Apr 19, 2021 7:52 am

Valdemar (not to be confused with Voldemort from Harry Potter, BTW) is the only data point I've heard of where his wear in the gear reduction unit finally wore out the teeth, and he never changed the fluid, illustrating Nissan has it so it will last around 150k miles, although the stuff may have gotten lumpy & nasty, more viscosity, lower range with letting it go like that.
Valdemar wrote:
Sat Oct 26, 2019 3:03 pm
While given the noise from my gearbox at 162,000 miles I wish I had changed the gear oil earlier the fact it is still going fine makes me think that unless you plan to push the car well past 200,000 miles changing of the gear oil is a waste of time and money.
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Re: How To: Reduction Gear Oil Change

Mon Apr 19, 2021 10:21 am

voltamps wrote:
Mon Apr 19, 2021 7:24 am
knightmb wrote:
Sun Apr 18, 2021 6:52 am
........ "uphill the entire way" drive from Franklin to Knoxville .....
That is "EV Central Country". Smyrna, Chattanooga, etc., I continue to read about more EV or battery factories there!! Do you get tours? Go to SAE Meetings in the area for cool meetings? That's car-country after all. Like Michigan with southern accents.
Yes, it is odd that of all places, this area is getting a new GM battery plant, already has the Nissan Battery Plant, and rumors about Mitsubishi also doing something with EVs here. These companies must have been offered some sweet tax rebates, probably no taxes forever or something to stick around. :lol: *Free* QC charging everywhere! Well, technically, they do tours at the Nissan Plant and the GM Plant has a welcome center for tours, never been on them, maybe I should visit and take pictures to show here. I've never been to the SAE meetings myself, only some of the "Drive Electric" events they have in the spring and fall where everyone gets together to show off their EV via a car show like format. A lot of people are from Michigan, just haven't adopted the accents yet, but we are working on 'em. :D
voltamps wrote:
Mon Apr 19, 2021 7:24 am
All that out of the way, if the Valvoline ULV (lower viscosity over all temperature ranges than Nissan Matic S) is causing the Gear Reduction Unit to operate at it's minimum friction (greatest range point), then some additional wear can be expected, over using Matic S or Redline D6 or Amsoil SS, any higher-visc ATF fluild. Notiice on the wear graph there really isn't much difference in wear, something around 10% extra wear from getting max Range here.
So basically get better range now and maybe in 150K miles need to replace the gears sooner? I can live with that. Would the extra 10% of wear show up in the oil if I changed it again in a few months and checked the magnetic plugs or is this something I wouldn't notice until I did another change at +100K miles for example?
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voltamps
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Re: How To: Reduction Gear Oil Change

Mon Apr 19, 2021 2:45 pm

knightmb wrote:
Mon Apr 19, 2021 10:21 am
So basically get better range now and maybe in 150K miles need to replace the gears sooner? I can live with that. Would the extra 10% of wear show up in the oil if I changed it again in a few months and checked the magnetic plugs or is this something I wouldn't notice until I did another change at +100K miles for example?
If we take Valdemar's experience as about what Nissan was shootin' for, and we know his (never changed) gears went 162,000 miles before failing, albeit with lumpy, tired, thick fluid inside near the end, then I'd guess you should be able to get 150,000 miles on the Vavoline ULV before the gears make funny noises. Given the merely 10% greater wear rate (estimated of course!) Valvoline ULV vs. Nissan Matic S, and also taking into account the fact you changed the fluid already and got the break-in metal junk off the magnets, yes 150,000 miles is probable.

The extra 10% wear is a rate, which means micrograms of steel mass shed per mile. That just means you get 10% less total miles than you would have gotten using Matic S. ... IF the analogy of the viscosity vs. wear rates from the graphs (above) holds up here. It's my best guess.
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Re: How To: Reduction Gear Oil Change

Sat Apr 24, 2021 3:00 am

voltamps wrote:
Thu Apr 15, 2021 8:25 am
( In nerdy engineer-speak, I'll ask them what the partial derivative of Range is with respect to gearbox oil KV100 in the Leafs they've tested before. )
A bit too nerdy for me, but there are two parts to this:

1. The gain in gearbox efficiency from using a different oil
2. The fractional contribution of gearbox losses to overall vehicle consumption

For example,
Say the gearbox is 5% of overall losses,
And a new spiffy oil reduces gearbox losses by 10%
That is good for a ~ 0.5% improvement in Wh/mile car consumption
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Re: How To: Reduction Gear Oil Change

Sat Apr 24, 2021 11:13 am

SageBrush wrote:
Sat Apr 24, 2021 3:00 am
Say the gearbox is 5% of overall losses,...
I too wonder about that first number. Of course speed matters to the answer, as aero drag goes up squared but most other losses are linear. So you'd have to pick a speed to ask that question at.

Some of the results seen here suggest the gearbox losses make up more than 5% of overall losses, otherwise the gearbox gains would have to be over 100%. I saw better numbers after my change to Redline last year, but then the weather also got better. Separating those two effects is difficult . . . you'd really have to put the first oil formulation back in to be more confident that the weather wasn't the larger contributor to the observed gains.

But, if the change is easy (cost and/or effort), then I see it as worth doing, even for small benefits. The benefits add up. It's talk of premature gear wear that starts pushing that decision back the other way.

It's been a very interesting discussion . . . several contributors have clear expertise in this area (voltamps for sure). It's been highly enlightening to read.
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