Is this oil too thin?

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FCD

FCD

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I've been looking for an ideal gear oil for my gearbox which specs SAE 80W, I found my local Shell station is selling Spirax S4G 75W80 GL4 oil.
Kv @100c is 8.1
KV @40c is 74
Viscosity index is 174
I believe it is full synthetic.
Most SAE 80W oils tend to be on the thicker side of the 80 grade , about 9 or 10cst.
I could get it for a very good price.
The gearbox has 300k miles on it and has a slight grind when downshifting from 3rd to 2nd, so i hope a thinner GL4 oil will give me better synchro action.
 
Merry Christmas FCD:
I would want something a little stouter with 300K.....maybe Redline's MTL.

MY 2014 Focus calls for Ford part # "SAE 75W API GL-4....Ford std. WSS-M2C200-D2" in it's MX-75 MT.
I would probably use that Shell stuff in a pinch but I only have 18K on the clock. At 300K, I'd like the extra margin of safety of the full synthetic Redline if I was staying with such a thin lube.

PS: I just noticed that this Shell product may be a full synthetic so maybe it will work fine...
 
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I ran 5w30 motor oil in my then new 84 Civic 5-speed as specified in the owner's manual. I used Mobil 1. At 200K I pulled the transmission and replaced the bearings, seals and gaskets because of bearing noise. Everything else looked good. I discovered with a used oil analysis that the oil sheered down quite a bit.

I put everything back together but used Red Line MTL. Now at 430K there are absolutely no noise and no problems. Everything looks good inside. There's no sheering problem with MTL.

This stuff costs a bit more but you use so little and change it so infrequently the cost is no problem especially considering that it really works well.
 
Originally Posted By: FordCapriDriver
I would love to use Redline MTL, but in Europe it's price is just too expensive.


Have someone ship it to you as a gift.
 
Originally Posted By: OneEyeJack
I ran 5w30 motor oil in my then new 84 Civic 5-speed as specified in the owner's manual. I used Mobil 1. At 200K I pulled the transmission and replaced the bearings, seals and gaskets because of bearing noise. Everything else looked good. I discovered with a used oil analysis that the oil sheered down quite a bit.

I put everything back together but used Red Line MTL. Now at 430K there are absolutely no noise and no problems. Everything looks good inside. There's no sheering problem with MTL.

This stuff costs a bit more but you use so little and change it so infrequently the cost is no problem especially considering that it really works well.



Congrats on 430K....I'm thinking that this proves that 5w30 (motor oil) works BUT is not optimal in certain MT's.
They probably spec'd motor oil for convenience sake...In other words, if I had a car that spec'd motor oil in the MT, I'd change to a thin gear oil ASAP...
 
I would rather use something little thicker-like Castrol 75w90 Multivehicle GL4 synthetic or Castrol 80w90 GL4 mineral. Multivehicle is a bit expensive, but rather good, at least on a relatively modern cars.
 
I do have a bottle of Ford 75W90 GL4 oil lying around, but i am rather confused on using it or not, since i have also read a thinner oil should make the synchros function better , since i currently have a slight noise when downshifting from 3rd to 2nd, i think right now it has some sort of 80w90 GL4/GL5 oil in it.
 
I'm not sure thinner will make the synchro work better, at least for long! That's also not what I felt when I experimented with gear oils (of course mine is a transaxle with only a bit more than 300K Km now so shearing might be greater). Or maybe the thicker oil dampened the noise more?

Well, I'd say +1 on Castrol Syntrans multivehicle which is a great GL4 oil.
 
Originally Posted By: FordCapriDriver
I've been looking for an ideal gear oil for my gearbox which specs SAE 80W, I found my local Shell station is selling Spirax S4G 75W80 GL4 oil.
Kv @100c is 8.1
KV @40c is 74
Viscosity index is 174
I believe it is full synthetic.
Most SAE 80W oils tend to be on the thicker side of the 80 grade , about 9 or 10cst.
I could get it for a very good price.
The gearbox has 300k miles on it and has a slight grind when downshifting from 3rd to 2nd, so i hope a thinner GL4 oil will give me better synchro action.

The bearings and gears in this 300K GB survives, mainly because of thicker gear oil ... probably ISO150 in 80W90 or ISO220 in SAE 90.
This S4G 75W80 GL4, which is ISO 68 gear oil, can't protect your bearings etc better than before.
Just my deduction.
 
Yeah, I agree. 75w80 is rather thin for gearbox like on this Capri. Those grades were introduced for FE in modern vehicles, not for better shiftability or better protection.
Years back I've tried 75w80 in a early 70 RWD car and it was disaster. Shifting was poor, gearbox noisy and it leaked like mad. I guess those old gaskets didn't liked low viscosity synthetic.
Edit; I would try. 80w90 mineral. That would be best suited IMO.
 
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Ford/Motorcraft MTFs are high quality. People actually used it (the FWD/ transaxle version) in other makes like Peugeots' and Opels as a upgrade over standard fluid and as a cheap alternative to the Castrol or Motul MTFs.
 
Originally Posted By: OneEyeJack
Originally Posted By: FordCapriDriver
I would love to use Redline MTL, but in Europe it's price is just too expensive.


Have someone ship it to you as a gift.


He doesn't want it. I DO!
 
Originally Posted By: FordCapriDriver
So i am better off with a 75W-90 or 80W-90

From components protection perspective, 80W90 (typically ISO 150) is preferred to 75W90 (typically ISO 100).

Originally Posted By: FordCapriDriver
I already have a bottle of Ford BO 75W90 GL4 MTF Mineral oil, i'll just get another one and that's it then, it only takes 2 Liters.

.... am in a dilemma for I hate left new serviceable oil unused .....
but I really believe you should use 80W90 to 'more assuredly avoid' total breakdown of this GB in its remaining life.
It's your take really.
confused.gif
 
It specifies SAE 80W, so i think a 75W90 will be thick enough, if it has survived for nearly 500 thousand kilometers and 41 years with almost no fluid changes on mostly 80w mineral cheap oils i think it will survive.
 
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