This is why Redline D6 is not the best ATF in Prius

Why not just use a good oil like Mobile1 5w-30?

 

The gentleman is talking about ATF oil...NOT engine oil. And...it's MOBIL.....NOT Mobile !

 

Very good info ! Thanks for posting it. Would still be best to stick with Toyota's WS while under warranty.

 

My spelling mistake, thanks for pointing it out, and I know exactly what he is talking about.

So....

Why not just use a good oil like Mobil1 5w-30?

​

 

Well sir,......... primarily because Mobil 1 5W30 is an ENGINE oil, NOT a Transmission oil, whoch is what Friendly_Jaceks post is all about. For your additional info 5W30 is not the oil recommnded for use in the
Gen 3 Prius engine. 0W20 is, and the GF5 SN Toyota oil is the optimum oil for it. GREAT OIL !

 

If a mechanic knowingly uses a non-WS-spec ATF, and there's a transmission loss, then isn't he or she liable for the loss?

Sure, D6 is probably fine, and I think it used to be spec'ed WS, but that specification is no longer listed on it, for whatever reason. D6 comes up as the ATF for the 2010 Prius, on the Redline Oil website, though.

So, use the ATF of your choice, but be aware of what you're using.

Time for a few runaway Priuses so we can discuss something more serious...

 

OK mouth, you have had your turn. Now let Friendly_Jaceks address my questions.

Friendly_Jaceks, what other "ATF" lubricants have you spec'd?

Have you spec'd any lubricants that are not specifically marked "ATF"? Like gear lubricants or MTF lubricants, or, dare I say, engine lubricants? Calcium sulfonate detergent is also in lubricants other than "ATF."

 

OK.

 

But you wont find much if all you do is look under the same rock.

Carry on.

 

It would be more impressive if there were some metrics of the different oils in a Prius transaxle:

• rolling friction testing - easier if wheels off the ground and measure the 'gear' and stirring drag
• operating temperature - the difference between internal and external temperatures under known conditions

To do the tests right, two changes are needed. The first to dilute the residual oil and a second one to complete the change. But this is something a Prius owning advocate could perform:

1. First change to test oil
2. Drive 1,000 miles to throughly dilute the residual
3. Prepare an instrumented oil plug temperature sensor
4. Second change to test oil
5. Sample for baseline oil test from second lot
6. Normalize tire pressure to known value
7. Drive 30 minutes on cruise control, highway speed recording:
   • MG1, MG2, external temperature, and oil plug temperature
   • ICE rpm and MG1 torque the primary metric of input power
   • Note wind speed relative to path
   • Repeat in opposite direction

The key metrics will be the oil plug temperature versus external temperature. The dT is a direct measure of how much warmer or cooler the test oil is running. Secondary metrics are MG1/MG2 and external temperatures since these are dominated by the electrical path, energy flow. But the stator temperatures are cooled by the oil and the dT of oil pool versus MG1/MG2 stator temperatures give a clue as to how well it is taking away the heat or leaving them running hotter or cooler than before. The ICE rpm and MG1 torque give the engine input energy to make sure the tests are 'normalized.' (*)

Remember, 'heat is the enemy' and I would go with the oil having the lowest temperatures of MG1/MG2 under known, as identical as possible, conditions. But I have no 'dog in that fight' for an alternate transaxle oil.

I did a literature search looking for lower viscosity lubricants compared to Type WS and had no luck. Since viscosity is the primary 'stirring loss' metric, I didn't see any reason to test other oils. But I am open to someone 'doing the experiment.'

Bob Wilson

* - Sorry for the awkward phrasing . . . a mix of 'Bob' and engineering . . . it is more a collection of test requirements than a layman's description of what is needed. Think outline that could and should be refined.

 

I might try Amsoil ATL in mine at the next fluid change, which will likely happen in March. I can run it for 30k and UOA.

However, I would guess that any improvements in wear would be minimal at best.

 

Thank you Friendly Jacek for the information on Redline D6. Being that I'm a fan of Redline oils, I was going to change to D6 very shortly! Guess I'll stick to Toyota's WS Trans oil.

 

These remarkable Prius seem to have very long lasting engines and transaxles. Other than the 2001-03 Prius and even in that model line, low rates, we're not seeing failing engines and transaxles. If transmission and engine rebuilders had to live on Prius-like failure rates, they would starve ... like the brake and exhaust shops already.

I fully admire efforts to improve the life-time of our vehicles but suspect advances in accident avoidance would provide substantially more 'bang for the buck.' Our real risks are hitting or being hit by other cars, poles, bridges, guard rails, e.t.c.

Don't stop lubrication studies as these hybrids have unique engineering characteristics. Just don't forget 'the elephant in the room' ... accidents.

Bob Wilson

 

Redline has recommended D4 for the Gen II Prius as of last year.

And Bob I can't see how rolling resistance means anything. No matter how good the fluid is it's not going to help rolling resistance. There's so many moving parts and resistance to begin with. I'm talking the difference between 2 fluids.

 

Calcium as an additive is usually used to reduce acidity in the fluid. That's what attacks plastic.
D6 virgin UOA shows zero calcium as an additive.
I have a virgin D6 TAN number of 2.38 (green good) and a TAN number 25,000 miles later of 2.56 (yellow showing slight acidity increase). I would imagine my next UOA will show even less TAN.

So D6 TAN wise is doing very well over 25,000 miles but showing a slight acid increase. Thats not an issue with my OCI and still not bad considering there's no calcium additive. I still prefer a 100% pure ester base stock.

And of all the UOA's I see other people post here most don't even show TAN.
TAN and TBN are the most important numbers. WEARCHECK INC always shows TAN number.

Redline has not been forthcoming on why they started recommending D4 instead of D6 for the Prius. I called Dave there last year and he said running D6 is fine but the Engineering staff recommends D4. He had no reason. Maybe this is it but I thought it may be its viscosity. Its a very thin 10 weight fluid. Thinner than D4.

Where is the UOA on Redline D4 that your quoting?