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Let's talk fluids


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33 replies to this topic

#1
AhmadHasib

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About to do an oil change on the Miata. Wanted to know which oil you prefer and how often you change it.

While we're on topic, which fluids are you using for brakes, transmission, differential, coolant, etc. and how often are you changing it?

#2
Rev

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You will get a million opinions on this topic :-) There's really good info available on miata.net and bobistheoilguy.com, but I'll give my two cents. I've run a lot of different motor oils in my Miatas, but always stuck with full synthetic to better handle the high RPM and heat on track. I currently use Mobil 1 10W30 but have had good success with Rotella full synthetic as well. You can go with increased viscosity in summer heat and lower viscosity in winter if you desire, but it's not been an issue for me. My old Miata (a '96 with 180k miles) had bad valve tappet noise. A 5W oil seemed to help lessen that. My newer Miata doesn't have that problem so I've gone back up to 10W. 

 

The key on engine oil is to change it frequently if you're pushing the car hard. I aim for about twice per track season (so twice a year). More often if I have a bad shift and run the engine over the rev limiter. 

 

Also, use good oil filters. I stick with OEM after hearing lots of advice on the matter. 

 

As for other fluids:

- For manual transmission and diff, it's hard to beat Redline. I use MT-90 for the tranny and 75W-90 for the diff (make sure to get the LSD friendly version if you have an LSD). I change these about once a year, depending on how much track time the car sees.

- For brakes I've run a number of different fluids. I currently run Motul RBF600 and have no complaints. Change every 6 months (required). Bleed after every HPDE weekend if you are driving hard on R-comps or similar tires. While you're at it, flush the clutch fluid, too, if it's black and hasn't been done before.

- For coolant I recommend going with as high a % of distilled water as possible. Antifreeze is a mess if it spills on track and can ruin a lot of people's weekends. To that end, I try to run 90%+ distilled water and just keep the car out of freezing weather. I also run water wetter, partly for the increased cooling efficiency, mostly for the corrosion protection. 100% distilled water is a no, no due to corrosion potential. 



#3
robertcope

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Fluid discussions are always amusing. So much BS tossed around.

 

I ran M1 0W-40 in my Miata. I run it in my S2000 and NSX, too, though this OCI I put Red Line 10W-30 into the NSX. I run Red Line fluids in my transmissions and diffs. I've used RBF600 brake fluid in everything except the NSX, which runs SRF.


Robert B. Cope

 

#53 - 2003 Jetta (red)
#53 - 1999 Miata (silver) aka GONK: "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
#94 - 2001 S2000 (red) aka Crisis

#XX - 1992 NSX (red)


#4
Rev

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Fluid discussions are always amusing. So much BS tossed around.


Please let me know if you detect any BS in my recommendations :-) In all seriousness, I am always looking to learn new and better ways to maintain my cars, so really do let me know if you'd disagree with any of my suggestions.

#5
hornetball

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FWIW, I've never used anything other than regular parts-store DOT4 on any Miata.  Never had an issue.  Miata brakes are generously sized, the car is light and the low power limits top speed.

 

Besides saving money, using less expensive and easily found fluid encourages you to flush often, which is the more important thing to do.


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#6
V6Donut

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I run:

AMSoil Dominator for engine 5-20

AMSoil syncrosmesh in trans

AMSoil Severe gear in diff

 

Castrol SRF for brake and clutch fluids.  



#7
Shuka

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My take on fluids, YMMV.

 

Considering the frequent change interval for engine oil, I use whatever is on sale at Autozone. Full synthetic for my fancy hot-running Honda. For the Miata motor, I used plain old conventional motor oil. For the cost of a single change with fancy engine oil, you can do 2 or 3 or more conventional oil changes.

 

For transmission, I've used Redline MTL, but most recently, Autozone gear oil. High end MTL and Miata synchros don't seem to play nice, but that may be just my experience.

 

For the differential, if you have a Torsen, use straight up gear oil. Nothing with friction modifiers (avoid the stuff with additives for "limited slip" use.) The torsen is designed for use with a specific amount of fluid friction; if you use something that messes with that, the diff won't work nearly as well.  If you have a VLSD, the limited slip mechanism is sealed up in the housing, so any gear oil will work. If you have no LSD, then whatever gear oil you like.

 

For brakes I've always used the ATE superblue and now yellow stuff. Same in the clutch. You won't feel a performance difference with high end vs low end as long as there aren't bubbles in the fluid, so again, probably not worth the highest end fluids when regular flushes are much more beneficial anyway.



#8
robertcope

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I like MT-85 in the Miata gearbox.

 

Red Line makes an "NS" diff fluid, which is what I use in my Torsen diffs: https://www.redlineo...x?pid=47&pcid=7 Many people don't understand that while the Torsen doesn't have clutches, it does rely on friction to work properly.

 

Agree with the brake fluid strategy; if ATE or whatever works, there's not much point in using SRF or any better fluid. Well, maybe. The SRF may require fewer bleeds throughout the season, which may end up being cheaper.


Robert B. Cope

 

#53 - 2003 Jetta (red)
#53 - 1999 Miata (silver) aka GONK: "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
#94 - 2001 S2000 (red) aka Crisis

#XX - 1992 NSX (red)


#9
Rev

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For the differential, if you have a Torsen, use straight up gear oil. Nothing with friction modifiers (avoid the stuff with additives for "limited slip" use.) 

 

Craaaappppp! I always assumed the Redline 75W90 was exaclty the right stuff to use with a Torsen since Redline specifies it's for LSD's in contrast to their 75W90ns. And I just changed it. Well, live and learn. I guess I'll switch at some point in the future and try it out to see if I can tell the difference. 

 

Overall, looks like I've been spending a bit too much on fluids, especially brakes. That'll help the bottom line :-) 



#10
robertcope

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Craaaappppp! I always assumed the Redline 75W90 was exaclty the right stuff to use with a Torsen since Redline specifies it's for LSD's in contrast to their 75W90ns. And I just changed it. Well, live and learn. I guess I'll switch at some point in the future and try it out to see if I can tell the difference. 

 

I wouldn't loose any sleep over it. Odds are you'll never be able to tell the difference.


Robert B. Cope

 

#53 - 2003 Jetta (red)
#53 - 1999 Miata (silver) aka GONK: "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
#94 - 2001 S2000 (red) aka Crisis

#XX - 1992 NSX (red)


#11
Shuka

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I wouldn't loose any sleep over it. Odds are you'll never be able to tell the difference.

 

That's probably true. Lots of people run whatever in a Torsen and they still work. It may be that friction modifiers are simply not required, not necessarily detrimental.

 

I've been lead to believe the NS is what you should use though for maximum Torsenness.

 

Here's a good chunk of info on the issue:

 

http://mazdaracers.c...choice-redline/

 

Of particular note, as mentioned in the above link, the "shockproof" stuff with solid particles for cushioning should be avoided. I have heard it can result in cataclysmic failure of the rear end!

 

HAHA! I just read down that thread and saw Robert's post about having used shockproof for many days with no issue. So there. Run whatever. Lol.



#12
robertcope

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HAHA! I just read down that thread and saw Robert's post about having used shockproof for many days with no issue. So there. Run whatever. Lol.

 

Well, after talking to davew (I think), I flushed my diff and put in NS. But yeah, I don't know that I could tell any difference.


Robert B. Cope

 

#53 - 2003 Jetta (red)
#53 - 1999 Miata (silver) aka GONK: "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
#94 - 2001 S2000 (red) aka Crisis

#XX - 1992 NSX (red)


#13
cabowabo

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Even on street driving I notice a difference between anything with friction modifiers and Redline NS. Dunno how much of a difference it makes on the stopwatch, but it definitely feels like it's distributing more torque with no modifiers. Of course, we know how reliable butt dyno's are.



#14
Shuka

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We haven't addressed coolant per the OP's request...

 

I do not run the blue toilet water that OEM hondas run, nor do I run antifreeze. (Race class requires water with no glycol since it makes the track super slick if it spills.)

 

I run Royal Purple "Purple Ice" coolant additive and straight water, and it seems to work pretty great. It's also nice to not have the sticky glycol everywhere when I have to drain the radiator, and in times like MSRH when a hose ruptures I didn't grease down the track with glycol. In addition I like that it won't kill plants and animals like antifreeze will, so I don't worry when it spills all over the floor or runs down the driveway.



#15
robertcope

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Good point. In the Miata I ran water + Red Line WaterWetter.

 

I'm debating what to do in the NSX, but given the climate here and the fact that I put it on track, it may be getting the same treatment.


Robert B. Cope

 

#53 - 2003 Jetta (red)
#53 - 1999 Miata (silver) aka GONK: "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
#94 - 2001 S2000 (red) aka Crisis

#XX - 1992 NSX (red)


#16
robertcope

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like MSRH when a hose ruptures I didn't grease down the track with glycol

 

I said I was sorry!!!!!!!

 

Seriously, I know that wasn't directed at me, but since I had this happen yesterday, it's a good point. Thankfully there were only a few cars on track, but I know both of them hit the coolant and had issues. One race prepped Miata went off at 100+mph, thankfully no damage or anything that they have mentioned. The other was a two week old BRZ, also thankfully no damage.

 

I've also hit coolant on track and have seen what it can do, it's not very fun!


Robert B. Cope

 

#53 - 2003 Jetta (red)
#53 - 1999 Miata (silver) aka GONK: "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
#94 - 2001 S2000 (red) aka Crisis

#XX - 1992 NSX (red)


#17
V6Donut

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We haven't addressed coolant per the OP's request...

 

I do not run the blue toilet water that OEM hondas run, nor do I run antifreeze. (Race class requires water with no glycol since it makes the track super slick if it spills.)

 

I run Royal Purple "Purple Ice" coolant additive and straight water, and it seems to work pretty great. It's also nice to not have the sticky glycol everywhere when I have to drain the radiator, and in times like MSRH when a hose ruptures I didn't grease down the track with glycol. In addition I like that it won't kill plants and animals like antifreeze will, so I don't worry when it spills all over the floor or runs down the driveway.

 

 

I said I was sorry!!!!!!!

 

Seriously, I know that wasn't directed at me, but since I had this happen yesterday, it's a good point. Thankfully there were only a few cars on track, but I know both of them hit the coolant and had issues. One race prepped Miata went off at 100+mph, thankfully no damage or anything that they have mentioned. The other was a two week old BRZ, also thankfully no damage.

 

I've also hit coolant on track and have seen what it can do, it's not very fun!

 

 

 

So a friend the other day told my about his accident into a wall and said it was because of coolant. continued to tell me I am an asshole because I have coolant right now. 

 

I guess, I should remove it and fill with distilled water + a water modifier.



#18
robertcope

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So a friend the other day told my about his accident into a wall and said it was because of coolant. continued to tell me I am an asshole because I have coolant right now. 

 

I guess, I should remove it and fill with distilled water + a water modifier.

 

Haha, I'm not sure it makes you an asshole unless some huge percent of folks on track are also assholes. Let's be real. Most of us take our street cars out there, and they're going to have antifreeze in them.

 

Maybe we could all move to aircooled Porsches.


Robert B. Cope

 

#53 - 2003 Jetta (red)
#53 - 1999 Miata (silver) aka GONK: "She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself."
#94 - 2001 S2000 (red) aka Crisis

#XX - 1992 NSX (red)


#19
V6Donut

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Haha, I'm not sure it makes you an asshole unless some huge percent of folks on track are also assholes. Let's be real. Most of us take our street cars out there, and they're going to have antifreeze in them.

 

Maybe we could all move to aircooled Porsches.

 

I dunno, I figured he was right. haha!

 

air cooled Porsche sounds like a expensive hobby.



#20
hornetball

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Ahhhhh . . . anti-freeze:

 

https://youtu.be/kZBXgYloDhQ?t=370


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