Good point "wulimaster". It is a transaxle. With regard to the statement..."the extent of frictional losses in a MANUAL transmission are only in the order of 1%-2%,in other words,the mechanism is about 98%-99% efficient. I do not agree based on my personal experience with MY CAR. LIke I've said previously,I swiched to Amsoil MTF and now consume 2 litres less per trip to work. In other words,the Honda MTF was not very efficient!
Amsoil "mtf" testomonial: "2 thumbs up"!
- Thread starter airbus
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"Keith". First of all,I have NOTHING to gain from sharing with you fellow BITOG members my personal results after having switched manual transmission fluids. I do not suffer,as far as I know, from any psychological disorder which causes me to lie or attract attention for myself. All I have tried to do is to convey my "testomonial" - respectfully,draw your own conclusions. I give you my word that the mileage improvement is true and ACCURATE. I just filled my car up again and it took the same 18 litres to fill. Something is causing a 2 litre savings! Lets debate this difference in opinion as factually as we can. With all do respect,the "driveline/transmission" efficiencies are hypothetical/"rules of thumb" if you don't mind me saying. Neither you,nor I know with any degree of certainty,what the ACTUAL driveline efficiencies really ARE for a Honda Civic or any car for that matter. For example. The standard,excepted rule of thumb that a manual transmission always is "x" factor more efficient than an automatic transmission is not true in all cases. Some cars are pretty close in terms of driveline efficiencies when manual transmission and automatic transmissions are concerned. With regards to this topic,all we,or I,know with 100 % certainty (not theorectical deduction) is that after putting the new Amsoil MTF in my manual transmission,is that I am saving 2 litres per trip. Remember Keith,the world is flat,not round. Thats a joke. Have a good day.
"keith",I forgot to mention - Don' forget,the Amsoil MTF is a THINNER fluid. How much that makes a difference is anybodys guess. I will guess that it's 2 litres (partly).
I found this somewhere a long time ago:
"The efficiency of a manual transmission drive train can be closely estimated by multiplying together the efficiencies of each loaded gear pair
or other working mechanism of the complete drive train. For helical gear gears used in transmissions in an EV at torques averaging 20% to 30% of max and with a low loss lubricant, the efficiency should average around 0.97 per gear pair. An allowance is needed also for the other operating but unloaded gear pairs, since they are resisting by some friction and continually churn the lubricant. An 0.99 factor is considered adequate for these unloaded gears. The Fiesta 4 speed gearbox then, which uses but one gear pair at a time, under these conditions has an efficiency of 0.97 x 0.99 or 0.96. Counting the differential drive, another helical gear pair
and 0.97 factor, the motor-t-drive axle efficiency becomes 0.93.
Manual transmissions typically used in front engine rear axle drive cars (those with 1:1 ratio for "high" gear) are connected "straight through"
and load none of their gears when in "high". Efficiency then averages about 0.98, with the moderate 2% loss going into the unloaded but
lube-churning gears. In the lower gears, however, these "straight through" transmission must use two helical gear pairs, so the gearbox efficiency
alone becomes about 0.97 x 0.97 = 0.94.
There are still more drive train losses before power reaches the driving wheels. While constant velocity U-joints are low-loss devices as are ball
or roller bearings, considerable and frequent angularity changes (such as in front-drive axles) cannot be achieved without considerable sliding and rolling friction losses. 2% loss, or 0.98 efficiency, is reasonable for modern front drive axles, (including the bearing and seal losses). For front engine, rear drive cars, a 1% allowance for drive shaft u-joints is adequate (if joint angularity is small) and another 1% for typical axle bearings and seals. That breaks down the drive train efficiency like this:
Typical modern front-drive transaxle (Civic, Fiat 128, Fiesta, Rabbit)
Manual transmission
Number of loaded gear pairs 1. (0.97)
Allowance for idling gears: lube churning plus extra bearing and selector drag (0.99)
0.97 x 0.99 = 0.96
Differential Drive
Helical gears (0.97)
Drive Axle
(0.98)
Overall Efficiency
0.97 x 0.99 x 0.97 x 0.98 = 0.91
Transaxle with bevel gear axle (VW Beetle, Renault LeCar)
Manual transmission
Number of loaded gear pairs 1. (0.97)
Allowance for idling gears: lube churning plus extra bearing and selector drag (0.99)
0.97 x 0.99 = 0.96
Differential Drive
Bevel gears (0.96)
Drive Axle
(0.98)
Overall Efficiency
0.97 x 0.99 x 0.96 x 0.98 = 0.90
According to the text, modern front wheel drive transaxles seem to come in at around 10% total loss, including the CV joints, which is entirely believable. A minor change in fluid viscocity can't possibly improve efficiency by 10% and reduce all those losses to zero! If Honda could make such a minor change during manufacture and improve mpg by 10%, they would be all over it already. The US market may not put a huge value on mpg but many foreign markets do and Honda surely spend huge $$$'s to lower mpg's by a few percent.
A cheap 10% mpg gain would not be overlooked.
"Something not right here".
"The efficiency of a manual transmission drive train can be closely estimated by multiplying together the efficiencies of each loaded gear pair
or other working mechanism of the complete drive train. For helical gear gears used in transmissions in an EV at torques averaging 20% to 30% of max and with a low loss lubricant, the efficiency should average around 0.97 per gear pair. An allowance is needed also for the other operating but unloaded gear pairs, since they are resisting by some friction and continually churn the lubricant. An 0.99 factor is considered adequate for these unloaded gears. The Fiesta 4 speed gearbox then, which uses but one gear pair at a time, under these conditions has an efficiency of 0.97 x 0.99 or 0.96. Counting the differential drive, another helical gear pair
and 0.97 factor, the motor-t-drive axle efficiency becomes 0.93.
Manual transmissions typically used in front engine rear axle drive cars (those with 1:1 ratio for "high" gear) are connected "straight through"
and load none of their gears when in "high". Efficiency then averages about 0.98, with the moderate 2% loss going into the unloaded but
lube-churning gears. In the lower gears, however, these "straight through" transmission must use two helical gear pairs, so the gearbox efficiency
alone becomes about 0.97 x 0.97 = 0.94.
There are still more drive train losses before power reaches the driving wheels. While constant velocity U-joints are low-loss devices as are ball
or roller bearings, considerable and frequent angularity changes (such as in front-drive axles) cannot be achieved without considerable sliding and rolling friction losses. 2% loss, or 0.98 efficiency, is reasonable for modern front drive axles, (including the bearing and seal losses). For front engine, rear drive cars, a 1% allowance for drive shaft u-joints is adequate (if joint angularity is small) and another 1% for typical axle bearings and seals. That breaks down the drive train efficiency like this:
Typical modern front-drive transaxle (Civic, Fiat 128, Fiesta, Rabbit)
Manual transmission
Number of loaded gear pairs 1. (0.97)
Allowance for idling gears: lube churning plus extra bearing and selector drag (0.99)
0.97 x 0.99 = 0.96
Differential Drive
Helical gears (0.97)
Drive Axle
(0.98)
Overall Efficiency
0.97 x 0.99 x 0.97 x 0.98 = 0.91
Transaxle with bevel gear axle (VW Beetle, Renault LeCar)
Manual transmission
Number of loaded gear pairs 1. (0.97)
Allowance for idling gears: lube churning plus extra bearing and selector drag (0.99)
0.97 x 0.99 = 0.96
Differential Drive
Bevel gears (0.96)
Drive Axle
(0.98)
Overall Efficiency
0.97 x 0.99 x 0.96 x 0.98 = 0.90
According to the text, modern front wheel drive transaxles seem to come in at around 10% total loss, including the CV joints, which is entirely believable. A minor change in fluid viscocity can't possibly improve efficiency by 10% and reduce all those losses to zero! If Honda could make such a minor change during manufacture and improve mpg by 10%, they would be all over it already. The US market may not put a huge value on mpg but many foreign markets do and Honda surely spend huge $$$'s to lower mpg's by a few percent.
A cheap 10% mpg gain would not be overlooked.
"Something not right here".
airbus, did you have 290,000 kms/182,000 miles on the old fluid? If so, this may have something to do with it.
The Honda OEM MTF was changed every 30,000 miles - religeously. I am planning on changing the new Amsoil MTF every 30,000 miles as well.
There are Honda MTF VOA/UOA in the transmission UOA section. I don't think that the MPG increase was because of the lower Amsoil viscosity since the OEM fluid would probably have sheared down considerably especially if used for 182k miles. And, any fluid will use up the AW/EP additives. You probably would've since an MPG increase even if using new OEM fluid.
Airbus, thank you for the Amsoil review.
I'm a firm believer in more frequent fluid changes and using upgraded fluids if available.
'Boutique' synthetic fluids, IMHO, always were better then OEM fluids in every vehicle that I've put them in. Competition will only make these fluids better. I'm glad that Amsoil/SpecialtyFormulations came out with fluids to give Redline MT90 and MTL a run for the money. And, Neo/RoyalPurple/BG/Torco also make excellent manual transmission fluids.
Airbus, thank you for the Amsoil review.
I'm a firm believer in more frequent fluid changes and using upgraded fluids if available.
'Boutique' synthetic fluids, IMHO, always were better then OEM fluids in every vehicle that I've put them in. Competition will only make these fluids better. I'm glad that Amsoil/SpecialtyFormulations came out with fluids to give Redline MT90 and MTL a run for the money. And, Neo/RoyalPurple/BG/Torco also make excellent manual transmission fluids.
Well, my experience is that pilots have to be able to make mathematical calculations, airline pilots, holding a commercial rating would have higher overall proficiency than the average private pilot.airbus is Canadian. I imagine the same sets of rules, in essence, exist in Canada.
I don't doubt your numbers and sincerity. A more than 10% mpg improvement by changing the fluid (with only a slight reduction in viscocity) is an exceptional claim - requiring exceptional proof.
An efficient light duty low performance car like the Honda Civic is very likely to have about 10% loss in the transaxle, so to get a 10% mpg improvement, the crankshaft has to get directly connected to the wheels or the transaxle loss goes to zero. That's the math I don't understand. Even if the transaxle loss if a high 15%, cutting 10% (2/3rd reduction) out of that is still a tough sell. Currently I don't own a manual transmission car so it doesn't benefit me. Just curious how this can be justified.
This is such an amazing thread. How many engineers (or physicists) does it take to tell a bumble-bee he can't fly before he gives up and walks instead?
The assertion of 98-99% efficiency in a gearbox is countered by every dynamometer run I've ever seen or heard of. I certainly hope no one using the theoretical arguments against airbus are involved in our country's space program (The shuttle did not just explode; my math says it couldn't have!)
Thanks for the feedback, airbus.
The assertion of 98-99% efficiency in a gearbox is countered by every dynamometer run I've ever seen or heard of. I certainly hope no one using the theoretical arguments against airbus are involved in our country's space program (The shuttle did not just explode; my math says it couldn't have!)
Thanks for the feedback, airbus.
Thanks for the support guys/gals. I agree with you. Theory is just that.Theory! The Gemrans in WW 2 THOUGHT it was impossible for their communication codes to be broken.Guess what,the were broken.
airbus,
i have on occasion seen the kind of gains )(5% to 10%) you are talking about, but only when the engine and drivetrain are switched to low viscosity synthetics, from high viscosity petroleum oils.
i have never seen more than a 1% to 3% gain simply from switching over a transmission and differential. i have no doubt the gains you are seeing are real, but there is something else going on above and beyond simply switching transaxle fluid.
Tooslick
i have on occasion seen the kind of gains )(5% to 10%) you are talking about, but only when the engine and drivetrain are switched to low viscosity synthetics, from high viscosity petroleum oils.
i have never seen more than a 1% to 3% gain simply from switching over a transmission and differential. i have no doubt the gains you are seeing are real, but there is something else going on above and beyond simply switching transaxle fluid.
Tooslick
I wonder what the road horsepower is at 62mph in the civic. My guess is somewhere between 10 and 17 horsepower. A reduction of 1 - 1.7 horsepower due to frictional loses is all that should be required to post a savings of 10%.
Yeah, we don't need no stinking engineers using math and theories to design the Apollo moon landings or Shuttle now do we. Where would that get us.
Ironically, the Shuttle engines are more powerful than designed and that's why they can throttle to greater than 100% power. Or did they switch to synthetics? Hmmmm.....
Thi isn't about the math. It's about the reasonableness of a greater than 10% efficiency gain by a marginal reduction in transaxle fluid viscocity, in a vehicle that is already likely to be one of the most efficient on the road. I'm not aware of any explanation for such an astounding result, and none has been offered. So it's an unsolved mystery, not an argument.
I hear what you are saying. With respect to low viscosity engine oils,I have previously tried ultra low viscosity engine oil's such as "Torco SR1" and did not find that it made a much of a difference. There was an improvement but not as noticeable as with the transmission fluid. Only the transmission fluid was changed. I use Mobil 1 0w20 oil.
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