Manual Tranny Fluid Observations

1991 Civic Sedan owner here, 182k miles, original and only
owner. The owner's manual for this Honda prescribes either
ordinary 10W-30 or 10W-40 (depending on expected ambient
temperatures) for the manual transmission fluid (MTF), with
a change interval of 2 years/60k miles, whichever comes
first. Discussion here suggests that use of ordinary engine
oil is no longer appropriate, due to changes in engine oil
technology over the years. In addition, using instead OEM
Honda MTF has been said, anecdotally and by one
authoritative written source IIRC, to yield smoother
shifting. Smoother shifting of course implies less wear as
well.

Last week I made the switch to OEM Honda MTF. I do think the
shifting is smoother. Not by a lot, but I think what I
perceive when shifting gears is more than a placebo effect.

As a "BTW" when buying my MTF at the dealer's, I asked the
dealer parts folks and one of the service writers whether I
could increase the change interval. They said yes,
suggesting I go to at least three years.

Interest piqued, I figured more recent Honda Civic owner's
manuals might add more insight. The 2004 and 2005 manuals
give a change interval of 6 years/120k miles(!) for normal
conditions; half these numbers for "severe driving
conditions." Go back to 1998, and the interval listed is 6
years/90k miles for normal; 2 years/30k miles for severe.

The OEM Honda MTF cost me about $12 total for two quarts,
which completely changes out my Civic's MTF. Ordinary 10W-30
or 40, for good or bad, costs around $4 for two quarts right
now.

Per year cost ("normal conditions") of using OEM Honda MTF
and the more recently recommended intervals: Just about
exactly the same.

Manual tranny design has not changed much, if at all, from
1991 to the present. A manual tranny is still mostly a
collection of steel etc. gears and synchronizers etc.
mounted on a mainshaft etc. that rotate in the MTF. Barring
further evidence, ISTM the OEM Honda MTF is now for many
older Civic owners the preferred route to go, both from a
wear-and-tear standpoint and a cost per year standpoint,
assuming the limiting factor is years and not miles for
one's driving.

 

Thanks for the observations. Contamination of manual transmission fluid
comes from two sources, wear of synchros, gears and bearings, and
environmental water. There isn't much you can do about wear (except change
the fluid!) but if you live in a wet, humid, cold or damp area then you
should think about modifying maintenance intervals appropriately. If you
ford a lot of streams, for example...

Cheers.

Earle

 

Thanks for the observations. Contamination of manual transmission fluid
comes from two sources, wear of synchros, gears and bearings, and
environmental water. There isn't much you can do about wear (except change
the fluid!) but if you live in a wet, humid, cold or damp area then you
should think about modifying maintenance intervals appropriately. If you
ford a lot of streams, for example...

Cheers.

Earle

 

My personal opinion for manual tranny lubricant is to use synthetic
since it is not exposed to combustion contaminents and take advantage of
extended component as well as a significant difference with shifting
especially during cold weather.

Take a look at the RedLine site where synchronizer issues are discussed
under transmission fluids.

JT

 

My personal opinion for manual tranny lubricant is to use synthetic
since it is not exposed to combustion contaminents and take advantage of
extended component as well as a significant difference with shifting
especially during cold weather.

Take a look at the RedLine site where synchronizer issues are discussed
under transmission fluids.

JT

 

JT, good point. The OEM Honda MTF container unfortunately
does not say whether it's synthetic or not. All it says is
that it's so superior that one can increase the time between
MTF changes.

Earle, unfortunately and unintentionally, right now each
year I end up driving through a few of what are in effect
serious creekbeds. Having also recently replaced that flimsy
little boot at the end of the shift rod linkage (just as it
enters the tranny casing), I can believe water ingress at
that point, for one, could occur on these "high rain" days
where the roads flood where I am. I should probably keep
count.

 

JT, good point. The OEM Honda MTF container unfortunately
does not say whether it's synthetic or not. All it says is
that it's so superior that one can increase the time between
MTF changes.

Earle, unfortunately and unintentionally, right now each
year I end up driving through a few of what are in effect
serious creekbeds. Having also recently replaced that flimsy
little boot at the end of the shift rod linkage (just as it
enters the tranny casing), I can believe water ingress at
that point, for one, could occur on these "high rain" days
where the roads flood where I am. I should probably keep
count.

 

Water in the tranny will show up as "milky" fluid. I have a Jeep. I know.
;^)

Earle

 

Water in the tranny will show up as "milky" fluid. I have a Jeep. I know.
;^)

Earle

 

Water in ANY oil that is churned in operation will result in a milky
emulsion.

 

Water in ANY oil that is churned in operation will result in a milky
emulsion.