?best motor oil to use in manual gearbox

[scoobie]

Hi, I have a 95 Dodge Colt/Eagle Summit/Mitsubishi Mirage.
It is made by Mitsubishi, and is made in Japan; it has a lovely 5 speed gearbox, matched to a 1.5l 85hp 12valve engine. I just bought a used gearbox from the wrecker, and I would like to drain the oil, and replace with synthetic. I have a good stock of synthetic motor oil, of various grades, so that way I wouldn't have to buy any gear oil for it. I heard that motor oil works just as well as gear oil, so what should I use: i have some Shell Formula 1 5w20 that has a hot cSt of 10-10,8 would this be ok, or should i use a slightly heavier 5w30? I also have some Quaker State synth 5w30, and Penz Plat, 5w30, and probably some synthetic 10w30 as well. I'd like to supplement it with 225ml of Molyslip MoS2 Gear Oil supplement, because I heard this is very good.

 

[Quest]

Sorry, I would disagree with you wholeheartedly on this one.

Check your manual for the proper type of MT fluid for use in Colt for if memory serves, it should be something like API GL-4 75W90.

Only Honda variants of MT can use something lighter but then again, Honda MTF fluid comes with AW/EP additives typical of all other MT gear lubes,something that you cannot account for in typical motor oil (or even just to add some MoS2 additives in it).

Q.

 

[aquariuscsm]

If its the same 5 speed that was in my 3000GT,it specs a GL4 75W90

 

[scoobie]

the manual calls for 1.8l of API GL-4 75w85 or 75w90
i was under the impression that engine oil has a similar viscosity to gear oil, and can be substituted.

 

[Solo2driver]

Use gearbox oil....completely different formulation of AW and EP additives than motor oil...that is a reason why Honda moved away from that and made their own MTF to replace the recommendations for fluid.

If it specs gear oil (GL-4 or GL-5), USE IT.

 

[scoobie]

I did some hunting on internet, and Mobil 5w30 synthetic is a good one:
http://www.allpar.com/fix/gear-oil.html
explains that Mobil synthetic 5w30 is safe for yellow metals, and should do the job nicely in a manual gearbox.

Any opinions about that article?

 

[TallPaul]

Depends, on my '84 150 at about 95,000 miles I drained the manual tranny and refilled with 10w40 motor oil of the day (1999) and the tranny still worked okay at close to 300,000 miles so the last owner told me.

If you do you probably need an additive for antiwear at a minimum. 1999 oil had more zddp than today's oils. Of course, some brands of tranny may not work well on motor oil, some will. Today's motor oils may have too much friction modifier for the syncros to work well. Surely you can do something else with all that motor oil and put something decent and appropriate in the gearbox.

 

[cos]

scobbie,

The Amsoil "Lookup Guide" shows your car calling for a 3.8 pints of a GL4 rated 75W90.

Since your in Ontario, and need two qts you might want to consider 1 qt of 75W90 (e.g. Redline MT90, Amsoil MTG) and one qt of 70W80 (e.g. Redline MTL, Amsoil MTF). I have 2 qts MT90 and one qt MTL in my 5 speed Mazda transaxle and it shifts beautifully in all temps.

 

[tdi-rick]

motor oil shears far too quickly in an MT, and the add package isn't optimal for synchro performance, so why not just use a dedicated MT fluid ?

Molakule has written some good articles on this. they are porbably in the tech articles section.

 

[scoobie]

they were recommending Mobil 1 extended formula to resist the shear. I'll go to the store in Michigan, and check out the redline and amsoil offerings. thanks for the tips.

 

[aquariuscsm]

Best I`ve ever used is Amsoil MTG. You`ll really feel a difference after it`s been in there for a couple of weeks.

 

[mechtech2]

The final update recommended Pennzoil Synchromesh.

 

[Toy4x4runner]

I've used redline MT90 IIRC... GL-4 Gear box oil. I used it in all my 1980's Toyota manual transmissions.

 

[scoobie]

I like the suggestion of Pennzoil Synchromesh. I read on the internet that it goes really well in several of the Mitsubishi gearboxes. I think I'll mix 50:50 Synchromesh with Pennzoil Gl4
80w90. Synchromesh is nice and thin, runs really well in cold weather, and helps to prolong the life of the synchronizers.

 

[Jaymus]

Redline MT90 seems to be some of the best stuff for transmissions needing a GL-4 spec oil. I put some GL-5 Mobil1 75W-90 in my wife's Eclipse a few months ago. Now 2nd gear grinds, and it grinds going into 5th. Well, for her, but either way, it wasn't like that before.

I got some MT90 and we are going to see how that goes. Going in tomorrow, sometime.

BTW, the M1 75W-90 has done fine in my 86 F-150's NP435 (4-speed with low) and it's been in there for even longer than her car. I still think I'm going to drain it out and put some MT90 in there.

 

[mechtech2]

Jamus - That M1 is a differential oil. M1 reps say not to use it in gearboxes because of yellow metal erosion and poor shifting.

 

[aquariuscsm]

Originally Posted By: mechtech2
Jamus - That M1 is a differential oil. M1 reps say not to use it in gearboxes because of yellow metal erosion and poor shifting.


^^2nd. Way back when I was trying to find a good manual tranny fluid,I emailed M1 and they told me not to use their gear oil in a synchronized manual transmission. Put some Amsoil MTG in there,you`ll be amazed at how well it does. It`ll smooth out your tranny in no time at all. Amsoil products do everything they claim they will do. I have MTG in my tranny and their GL5 80W90 in the rear diff. It`s all I`ll ever use again.

 

[Scott P]

Our MG called for motor oil in the transmission, but it is 38 years old. I put in some Redline MTL and it is shifting better than ever.

 

[aquariuscsm]

I think Amsoil manual tranny fluids should come OEM in all performance cars. If cars are now coming from the factory with synthetic oil,they should also come with the best tranny fluids.

 

[mechtech2]

aquiriuscum =- Good point. Makes you wonder what politics are involved.