FL5/DE5 Transmission fluid reference

[Spart]

Thank you for the deep dive!

FWIW, I was able to buy through Ravenol direct (last year, anyway) through their US website:

https://ravenol-usa.com/en

Unfortunately I haven't had the time or motivation to change fluids yet, factory fluid has been expectedly sufficient for my use.

They don't list STF there, which is kind of absurd considering it's specifically listed to meet GM/Mopar manufacturer specs and nothing else.

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[SlowAP2]

My

There's always somebody on an enthusiast forum who feels the need to say "don't modify your car! the warranty! the warrantyyyyyyyyyy!"

Maybe just don't volunteer that information to the dealer and they won't know. Pretty simple!

A lot of people on here are trying to get more longevity out of their second gear synchro. If Honda corporate were smart, they'd be on the same page.

My cars modified and know the risks of what I am doing . Just making sure its known incase someone cares about it. Maybe someone wouldn't have known and shared that info thinking it was harmless .

 

[AspecR]

Just an added FYI on this, the owners manual calls out specifically using Honda MTF, not just a GL-4 or specific weighted oil. If you use anything other than Honda MTF that's grounds for dealers and Corporate to deny warranty claims on your transmission.

It is shitty but I've witnessed this before with Honda and don't want to see anyone blind sided by not knowing.

This is true but the cases of Honda denying warranty claims based SOLELY on using a different transmission fluid are few and far between. There are other pieces to the puzzle that are missing like, removed CDV, upgraded clutch, cars been tuned , abnormal use and abuse, etc. Changed transmission fluid alone is not grounds for denial of warranty work

 

[Spart]

This is true but the cases of Honda denying warranty claims based SOLELY on using a different transmission fluid are few and far between. There are other pieces to the puzzle that are missing like, removed CDV, upgraded clutch, cars been tuned , abnormal use and abuse, etc. Changed transmission fluid alone is not grounds for denial of warranty work

I'm using a fluid that specifically bills itself as a direct replacement for "Honda/Acura Genuine MTF".

If Honda doesn't like that, they're going to get sued.

Maybe someone wouldn't have known and shared that info thinking it was harmless

The implication here being I should delete this thread.

Instead, I'm going to delete you. Welcome to the ignore list guy!

 

[Spart]

Manufacturer recommends changing at approximately 60k miles, I wouldn't let it pass 30k miles before doing a change. I did my first tranny fluid drain at 21k miles because my car is full bolt-on tuned so it's making considerably more power than stock.

Where specifically does this 60k figure come from? Google has people saying 30k, 60k, 100k. I believe the manual is silent on the issue, so it must come from some other document.

If there's a verified source for it, I will add it to the OP.

ETA: the manual is not silent on the issue, added info to the OP.

 

[AspecR]

Where specifically does this 60k figure come from? Google has people saying 30k, 60k, 100k. I believe the manual is silent on the issue, so it must come from some other document.

If there's a verified source for it, I will add it to the OP.

Intervals are determined by MM subcode 3, which varies depending the type of transmission the car is equipped with. For MTF which refers to replacement of transmission fluid generally occurs around 95k kms or 60k miles. Intervals are lower for CVT/AT vehicles. It does vary depending on time driven, time passed and driving habits.

The code can appear as low as 30k miles for MT equipped cars but that depends on usage. Most Type R owners swap their fluid before ever seeing that code though.

Source: Trust me bro lol, the tech that did my fluid change told me while I swapped to Redline MT-90

 

[Spart]

Intervals are determined by MM subcode 3, which varies depending the type of transmission the car is equipped with. For MTF which refers to replacement of transmission fluid generally occurs around 95k kms or 60k miles. Intervals are lower for CVT/AT vehicles. It does vary depending on time driven, time passed and driving habits.

The code can appear as low as 30k miles for MT equipped cars but that depends on usage. Most Type R owners swap their fluid before ever seeing that code though.

Source: Trust me bro lol, the tech that did my fluid change told me while I swapped to Redline MT-90

So what I'm getting out of this is: the longest interval that the digitized reminder in the car will fire off at is 60k?

 

[AspecR]

So what I'm getting out of this is: the longest interval that the digitized reminder in the car will fire off at is 60k?

Correct

 

[SlowAP2]

I'm using a fluid that specifically bills itself as a direct replacement for "Honda/Acura Genuine MTF".

If Honda doesn't like that, they're going to get sued.



The implication here being I should delete this thread.

Instead, I'm going to delete you. Welcome to the ignore list guy!

Little sensitive there bud?

 

[Spart]

Correct

I added a bunch of information on this sourced from the owner's manual to the OP.

 

[Spart]

Regarding trans fluid change intervals, here's an interesting clip from Lake Speed Jr on the how and why of it:



Going to add this to the OP as well.

 

[johnloov]

My goal is to change the gear oil every two oil changes, but want a quicker way to do it without taking the airbox out every time, and my understanding is the dealership has a method to do this.

Wondering has anyone tried to simply fill via a syringe via the 10MM check bolt and drain it from the bottom?

Technically this seems like it would work simply removing this 10MM Bolt while doing an oil change. Would this work Step 1) Remove 10MM bolt Step 2) Remove Trans Drain plug and Drain Step 3) Install Drain Plug with new Crush washer Step 4) Fill Trans Fluid with Syringe via 10 mm check hole 5) Install 10mm w/crush washer - Done.

CTA Tools 7073 Filling/Extracting Pump

https://www.amazon.com/gp/product/B015Q1JNBO/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1

I checked this size of the hole of the check bolt and seems a small syringe would work.

It seems this technically would work and would allow me to change it more often maybe after every 4 track days, much faster.

Anyone tried this, or see a problem with it?

Thanks!

This post is intended to be a one-stop collection of info about changing the transmission fluid in the FL5 CTR or DE5 Integra Type S.

Important: when changing transmission, transfer case, or differential fluid, ALWAYS REMOVE THE FILL PLUG FIRST. If you drain your transmission and then come to find out that you cannot remove your fill plug, your car is going to be parked for a while.

OEM Fluid

The OEM fluid in these cars is good old Honda MTF. According to the 2025 USDM Civic Hatchback owner's manual:

Honda doesn't specify a gear oil weight for this oil, however it's in the neighborhood of a straight 70W or 70W-75. Honda doesn't publish kinematic viscosities for MTF either, but these are the approximate kinematic viscosities of Honda MTF as reported by folks who have done VOA on new fluid:

7.265 cSt @ 100°C
30.70 cSt @ 40°C

Honda MTF is inoffensive but it can be improved upon. You can run any GL-4 gear oil intended for a manual transmission with a viscosity suitable for your use and expected ambient temperature range. Scroll down to the end of this post for suitable alternatives to the OEM Honda MTF.

Service Interval

The "Honda Maintenance Minder" in these cars tracks various maintenance intervals including transmission fluid. When the car thinks it needs a transmission flush, it will show code 3 in the cluster, along with any other codes that may be active. From the 2025 USDM Civic Hatchback owner's manual:

And also:

Note blurb #4 above: "Driving in mountainous areas at very low vehicle speeds results in higher transmission temperatures. This requires transmission fluid changes more frequently than recommended by the Maintenance Minder. If you regularly drive your vehicle under these conditions, have the transmission fluid changed every 37,500 miles (60,000 km)."

According to the UK 2024 CTR manual:

Honda states in the UK CTR manual that the transmission fluid should be replaced every 75k miles under "normal" use and every 37.5k miles under "severe" use. Severe use is defined in the UK CTR manual as:

Use your own judgement. It can't hurt to change the fluid early. In particular, many people advise changing the fluid after initial break in (600-5000 miles depending on who you ask.)

Here is industry expert Lake Speed Jr. on the how and why of gear oil change intervals:

​

Capacity

The capacity is 2.32 US quarts per the 2025 USDM Civic hatchback owner's manual.

If you found instructions that say to just put two quarts in, those instructions are wrong. You should fill the trans until fluid starts to run out the "check" plug, and if the car is level and fully drained, this will take more than two quarts. For me, this was about 2.1 or 2.2 quarts. If you buy a fluid that comes in liters, you can probably get away with getting two liters as this will be 2.1 quarts. If you're buying a fluid that comes in quarts, you need to buy three quarts and you'll have some left over.

Drain and fill plugs

The drain and fill plugs share a crush washer and torque spec. They accept a 3/8" drive socket extension, or a 3/8" male pipe plug socket such as a Sunex 312PC. I would highly recommend a 3/8" male pipe plug socket, because I ruined one of my 3/8" drive socket extensions removing the fill plug. It stated to break at the ball detent. The fill plug is insanely tight from the factory and I'm not the only one to experience this.

The crush washer is Honda part number 94109-20000 and you will need two of them.

These plugs should be torqued to 32 ft-lb.

Check plug

The check plug is a much smaller bolt with a 10mm hex head.

With the car level, fill the transmission with fluid until it starts to run out of the threaded hole for the check plug.

The crush washer for this plug is Honda part number 90442-R76-000.

This plug should be torqued to 9 ft-lb.

Plug locations

You will have to remove the airbox to access the fill plug, which is on the top of the transmission. For instructions on how to remove the airbox, reference the first part of Acuity's instructions for accessing the cable shifter bushings. In fact, consider replacing the cable shifter bushings at the same time, since they're nearby. You might also consider deleting your clutch master cylinder damper, which is under the battery bracket.

To access the drain and check plugs, you will need to remove the tray under the engine/trans as if you are changing the oil.

The drain plug is on the bottom of the transmission:

The check plug is on the side of the transmission facing the front of the car:

Suitable replacement fluids

While Honda MTF is recommended by the owner's manual, changing to a higher quality fluid can be an easy way to improve various aspects of your car.

Many fluids will give a smoother feel, and some may even help with the notorious Honda second gear grind. This isn't just about viscosity, it's primarily about friction modifiers and other additives.

If you are tracking your car, you may wish to use a higher viscosity fluid so that your viscosity at full operating temperature is in a more acceptable range.

If you are not tracking your car, a higher viscosity fluid may do more harm than good for the shift feel, particularly when the transmission is cold.

The most important thing is that you should use a GL-4 (and not a GL-5) fluid intended for manual transmissions.

This fluid need not have an LSD additive. While our cars do have LSD, they are helical (gear type) LSDs, and manual transmission fluids with LSD additives are intended for clutch-type LSD.

If you don't have a good reason to do so, you should not stray too far from the viscosity that Honda uses. Honda MTF is a 70W or 70W-75 oil. Using 75W-90 is a big step up from 70W-75 - it's nearly double the viscosity of Honda MTF - and it provides little benefit if you are not doing something to drive your transmission temperature to the moon - like driving on track.

When comparing a replacement fluid to Honda MTF, keep in mind that Honda MTL has these viscosity characteristics:

7.265 cSt @ 100°C
30.70 cSt @ 40°C

With cSt, a lower number means lower viscosity.

Regarding the 100°C viscosity figure specifically, a gear oil with a weight ending in 75 (70W-75 or straight 75W) should be in the range of 6.5-8.4 cSt @ 100°C

Fluids that closely match Honda MTF

These fluids have a viscosity range that is comparable to Honda MTF - 70W-75 or straight 75W.

If you are concerned about maintaining extreme cold weather performance under 0°F similar to the OEM Honda MTF, stick to these fluids or use Honda MTF.

BG Syncro Shift II (75W-75 GL-4)
7.11 cSt @ 100°C
37.85 cSt @ 40°C

Castrol Syntrans FE 75W
6.3 cSt @ 100°C
32.2 cSt @ 40°C

Pentosin FFL-3 (BMW MTF-LT-5 equivalent)
7 cSt @ 100°C
34.7 cSt @ 40°C

Pentosin FFL-4 (75W-80 GL-4 and BMW MTF-LT-1/2 equivalent)
7 cSt @ 100°C
34.7 cSt @ 40°C

Motul Gear Power FE 75W
5.8 cSt @ 100°C
30.7 cSt @ 40°C

Redline MT-LV (70W/75W GL-4)
6.3 cSt @ 100°C
29.9 cSt @ 40°C

Royal Purple Synchromax
7.5 cSt @ 100°C
39 cSt @ 40°C

Fluids one step thicker than Honda MTF

These fluids are in the 70W-80, 75W-80, or straight 80W range.

At least three of these fluids are very commonly used and recommended in our cars - ACDelco 10-4014, Redline MTL, and Amsoil 5W-30 MT Synchromesh. I am personally running Redline MTL.

Use these fluids if you do not need the best performance in sub-zero temperatures.

ACDelco Synchromesh 10-4014 (no weight specified, but close to 75W-80)
10.05 cSt @ 100°C
50 cSt @ 40°C

Motul Motylgear 75W-80
10.1 cSt @ 100°C
58.8 cSt @ 40°C

Redline MTL (75W-80 GL-4)
10.4 cSt @ 100°C
50.8 cSt @ 40°C

Amsoil "5W-30" Manual Synchromesh Transmission Fluid (note this is like a 75W-80 gear oil, no clue why they use the motor oil weight.)
10.1 cSt @ 100°C
49.4 cSt @ 40°C

Fluids two steps thicker than Honda MTF

These fluids are in the 75W-85 or straight 85W range.

Only use these fluids if you do not need the best performance in sub-freezing temperatures.

Motul Motylgear 75W-85
12.6 cSt @ 100°C
82.6 cSt @ 40°C

Redline MT-85 (75W-85 GL-4)
12 cSt @ 100°C
62 cSt @ 40°C

Fluids three steps thicker than Honda MTF

These fluids are in the 75W-90 or straight 90W range.

I would not recommend using these fluids if you drive in winter weather at all. However, they could be excellent for track use.

Motul Motylgear 75W-90
14.2 cSt @ 100°C
85.4 cSt @ 100°C

Redline MT-90 (75W-90 GL-4)
15.5 cSt @ 100°C
82 cSt @ 40°C

Amsoil 75W-90 Manual Transmission & Transaxle Gear Lube
14.0 cSt @ 100°C
80.3 cSt @ 40°C

I can't decide on a fluid - help!

Viscosity is not the only thing that matters for shift feel with a manual trans, though it can make a big difference in cold climates. Friction modifiers will alter the synchro feel, which is most of what you're feeling through the shifter. This is why what feels "right" in every gearbox will be subjective and oil from one brand won't feel the same as equivalent weight oil from another brand.

Climate and use also matters. If you live somewhere that doesn't really get winter, or you track your car, 75W-90 might be the ticket. But if you want like for like with OE, I would stick to 70W, 75W, or 75W-80 oils and pick your favorite based on friction modifiers (shift feel.)

Forum members have reported excellent results with Amsoil "5W-30" (actually 75W-80) Manual Synchromesh Transmission Fluid, Redline MTL, and ACDelco Synchromesh 10-4014.

In particular, ACDelco 10-4014 has long been a remedy for second gear grind in Hondas of various generations.

 

[Spart]

My goal is to change the gear oil every two oil changes, but want a quicker way to do it without taking the airbox out every time

The airbox in these cars comes out ridiculously easy compared to almost every other car I've ever worked on.

Remove the sensor and pull it back, release two snap-in clips for some other wires, four 10mm bolts, a 5.5mm bolt on the hose clamp, and it's out.

You will waste far more time than that attempting to pump fluid in through that tiny hole with a syringe. I believe the threads are M6?

If you are serious about doing this and want to spend some money and effort to gain any sort of efficiency, I would recommend purchasing something like this:

That could be threaded into the check hole. You'd want to add a rubber washer or similar to form a temporary seal. And double-check what the treads actually are, both size and pitch.

And then getting what you need to hook that up to a fluid transfer pump of some sort. This could be as simple as a repurposed brake bleeder with a large enough reservoir, for example:

https://www.rennline.com/schwaben-3-liter-european-pressure-brake-bleeder-sku-sch-2774831/

You would want to be very careful to measure out the exact right amount of fluid so you don't underfill or overfill. This would take some trial and error at first, doing things with the car completely leveled out. But once you figure it out, you could fill the trans from the check plug with only the front of the car elevated, since you will be putting in a measured amount of fluid.

I do not think this is worth it. There shouldn't be a need to change your transmission fluid every two oil changes. Track use changes things, but using a more appropriate viscosity fluid and making cooling system changes would be a better way to handle that - if the fluid is getting cooked on track, that's never a good thing no matter how often you change it out.

We are somewhat lucky with our cars in that they already at least have a cooler (or warmer, depending) for the trans that exchanges heat with the engine coolant. It's a matter of plumbing to adapt this into a dedicated trans cooler, and the transmission already has an internal pump.

Blackstone will do UOA of transmission fluid. This will give you an idea of how the fluid is performing.

 

[Spart]

Motive also has a larger version of their brake bleeder (one gallon vs 2 quart) that's specifically for this type of thing: https://www.motiveproducts.com/products/powerfill-pro-1-gallon-tank

I like that it has a ball valve, but I'm not sure what all fittings you would need. If you were to use the M6 to 8mm barb fitting like I posted, I would want to connect it to one of these:

https://www.motiveproducts.com/coll...eplacement-quick-release-male-female-fittings

That would let you make an adapter that you can thread on without a bunch of hose getting tangled.

Motive also sells spare clamps, hose, etc:

https://www.motiveproducts.com/collections/replacement-parts-accessories

 

[Jack90210]

Motive also has a larger version of their brake bleeder (one gallon vs 2 quart) that's specifically for this type of thing: https://www.motiveproducts.com/products/powerfill-pro-1-gallon-tank

I like that it has a ball valve, but I'm not sure what all fittings you would need. If you were to use the M6 to 8mm barb fitting like I posted, I would want to connect it to one of these:

https://www.motiveproducts.com/coll...eplacement-quick-release-male-female-fittings

That would let you make an adapter that you can thread on without a bunch of hose getting tangled.

Motive also sells spare clamps, hose, etc:

https://www.motiveproducts.com/collections/replacement-parts-accessories

I have one of those and they are excellent for this kind of job. Transmissions, differentials, transfer cases etc. Also, it's big enough to get a gloved hand inside of it, so I can wipe it out when switching from trans fluid to gear oil.

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