Motor oil + Gear oil blend in manual transmission?

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I have 0.75l of synthetic blend GL-4/5 gear oil sitting on the shelf. I need ~ 1.25l for my MT. I am thinking of blending in 0.5l of 5w-30 motor oil rather than buying some more gear oil. My thinking is that I wouldn’t mind thinning it out a little for the cold winters here -- and seeing how the concoction works.

Any issues in blending a motor oil and gear oil?

It’s for a 1987 1.8 MT-5-speed Jetta. The owners manual says Hypoid-oil SAE 80/80w-90 …Mil-L-2105 or API-GL-4. The Haynes manual says GL-5 80w-90.

I imagine that I would probably be giving up some wear protection, but it shouldn’t be too much considering a good portion of the mix is gear oil. I’ve seen several posts where in Honda MT’s they were actually spec’ing and using motor oils.
 
The motor oil may be a little slippery for your synchros, and doesn't have the EP and AW additives that you would like in there.
Amortize the $6-8.00 over the years of projected use of the car, and just go and get the correct fluid.
 
With the requirement for Hypoid compatible oil would recomend buying some more gear oil. Maybe try a full synthetic to aid low temp viscosity and shifting performance.
 
Hi there,

This post and the answers are so misguided, it is not even funny.


First, you should not use GL5 tranny fluid in VW Jetta manual transmission. The oil satisfies GL4 easy, but the GL5 spec means it has the EP additives which one of the posters warns to be too little. The EP additives will eat your synchros (brass will oxidize).

The only fluids which are readily available is Redline MT-90 or GM Synchromesh.

W115nut
 
quote:

Originally posted by W115nut:
Hi there,


This is not my car, and I don't intend to add anything to this technical discussion, but I noticed this is the first post for W115nut.

It shows the value of this site, that this person went to the trouble to register and join in here to add some advice that he (she?) feels qualified to give. It's why I am here several times a day.

Welcome to the site. (Someone else may post the cute little flashing welcome sign.)

edit: Whoa. Now that I got this written and posted, there are 10 posts. Going to be a busy poster?
wink.gif
 
If indeed the gearbox requires Hypoid gear oil, I would not blend engine oil into the fill. However, most gearboxes do not require hypoid oil and are relatively easy on the oil. I would blend in thicker engine oil, 5,10,15w40 would be my choice, and since a 40wt engine oil is close to 90wt gear oil if memory serves.

Some gearboxes spec'd engine oil. I have many quads that have dog style transmissions that spec 10w40, I also had a British built transmission that spec'd engine oil. I would prefer to use better oil for the application, however as long as the gearbox is not a hypoid type, then the engine oil will be adequate I think.
cheers.gif
 
Hello,

I think this is clearly a case where everyone has got an opinion. Could the original poster do us a favor by doing a simple google search for:

VW A2 GL4

or

VW A2 MT90

etc.

W115nut
 
W115nut, you and your google searches.
All google does is provide MORE opionions and rarely anything factual.

This forum is for asking fluid/filtration questions and getting answers. Answers are sometimes opinionated. Others might be based on personal experiences.

And, there are a bunch of GL5 fluids that are GL4 synchro safe and compatible, like SF or RP.

Drivebelt, you know your spec. Use a fluid that meets that required spec. If you want better winter performance, use a full synthetic that meets the specs.
 
Hi unDummy,

I have first hand experience with the same transmission. It is bulletproof with the right gear oil and fails with others.

You can find a lot more information on this at www.vwvortex.com and go to VW A2 forums (the 85-92 Golf/Jetta).

http://forums.vwvortex.com/zerothread?id=2676412


There are no GL5 fluids which are safe for this car. Redline MT90 is good but can cause leaks. If you can find dino GL-4 oil, it works the best in mild climates. MT90 advantage is mainly at lower temperatures in the north.

There is also a way to fill the transmission from the speedometer cable. I do not exactly remember if the fill hole was raised by the time 88 models rolled out. However, if you fill the 85-87 models using the fill hole, you do not fill the transmission to capacity through the speedometer cable hole and you will ruin the fifth gear in short time.

W115nut
 
W115nut,

020s are bulletproof until a few rivets holding the differential ring gear to the carrier come loose, get between pinion and ring gear, and manage to blow a hole through the transaxle case.

Rivets ... Of course in the field, rivets are replaced with conventional fasteners. It's no fun.

Reverse idlers tend to get ate up too, but that's mostly driver error or abuse.

Just what we see...

DH
 
Hi FazerZ,

There were some reports on the net that the two river related failures were primarily affecting GLI and 16V models with close ratio tranmissions which are abused and not this particular economy minded long ratio transmission especially if driven in a more leisurely pace.

W115nut
 
I just replaced the gear oil in my transmission on my '84 Rabbit. A couple of things I discovered:

It is really hard to find dino GL-4. But I did find a Gl-4 85W-90 at my local Napa. I'm not planning on sticking with this oil long term, just a few months (I'm going to run some Auto-Rx through it for about 1000 miles), then dump it and put in some 75W-90 GL-4 before colder weather hits. The oil I found at Napa is made by Sta-Lube and costs me about $5/qt. In addition to W115nut's suggestion of Redline or GM Syncromesh, Amsoil also makes a 75W-90 GL-4: http://www.amsoil.com/StoreFront/mtg.aspx

Also, I'll second W155nut's recomendation about staying away from GL-5 oils.
 
I'd use a 15W40 or a 20W50 engine oil. They'd be closer in weight to a SAE90 gear oil.
www.bobistheoilguy.com/visc.html

And if you feel like searching thru the VOA's look for an engine oil that's LOW in Moly (Mo). I've noticed MTF's are low in moly and that should help with the synchros. I think Delo or Delvac would fit the bill.

Coastal and Sta-Lube are the only 2 dino GL-4's that I've seen. Penzoil Synchomesh?

Redline 75W90NS is a GL-5 that would work.
 
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