gear oil vs motor oil

Eric_Phillips · Dec 28, 2008

There seems to be some people that are very knowledgeable about oils on this forum so I wanted to run a question about motor oils and gears oils past you. This all stems from trying to find a 90W gear oil that is compatible with yellow metals. One person said they use a non-detergent 40W motor oil since it has the same viscosity as 90W gear oil. Is this true? Also do you have any suggestions to find a gear oil that is compatible with yellow metals?

Diamondpilot · Dec 28, 2008

There are many gear oils that are safe for yellow metals. If you are working on a Chinese Tractor like a Jinma or Kama, which I guess you are, the consensus is if its a newer tractor there is no longer yellow metals in them. If you really want some info on this go to the Chinese Tractor section and type in the search "gear oil" and you will find tons of info.

I would not use 40W motor oil even though that is what it says in the manuals on many of these tractors. The consensus is that is all they have available in rural China and there are better oils like 80/90 gear oils with Extreme Pressure additives.

If you want to learn about oils look up in your yellow pages something like "Oil Distributors" They will sell small orders, like 5 gallon pales, to the consumer from the warehouse and the price is usually only a few dollars more than the WalMarts and Autozones but the knowledge is priceless.

Chris

Eric_Phillips · Dec 28, 2008

The oil is needed for an all American snowblower gear box from the 70's. The guys on the Yahoo Gravely list said to use motor oil. I am looking for a second opinion.

Diamondpilot · Dec 28, 2008

I am in the boating business. I would consider using a straight 90W outboard gear oil available at WalMart or any marina. I am not sure how much you know about boats so don't confuse it with the oil you need to mix with the gas in some 2 cycle outboards. This is the gear oil that goes in the lower unit where the forward and reverse gears are housed along with the rest of the drive line. I am guessing you need a small quantity, something like a few quarts so even though its pricey it is Yellow Metal Safe. It should run you about $5 per quart.

Here is a example: http://www.overtons.com/modperl/pro...&cname=Lubricants&aID=24C&merchID=1009&r=view

Here is another oil we use in older equipment: http://www.bp.com/liveassets/bp_int...a/STAGING/local_assets/downloads/b/BP7755.pdf

Chris

DieselPower · Dec 29, 2008

I would not suggest using a motor oil. Gear oils have a much higher level of extreme pressure additives than engine oils do. Also there are a lot of additives in engine oil that will serve no purpose in a gear application. You will find most (not all) gear oils these days are "yellow metal" friendly. Many you will find will have multiple API ratings, API GL-4 and GL-5 and MT-1. There is also no reason to have to use a single viscosity gear oil. You will probably have better luck finding a multi-viscosity gear oil like 80W/90. Actually, a 80W/90 would be better as it will have better cold flow properties then the straight weight oil will.

sld · Dec 29, 2008

I went thru this on my mid 80's Ford tractor front axle.

I finally went with a Napa house brand of gear oil that was GL4 compatible and it was only 2.50 per quart.

If you have a local Napa, try them. If not, just look for something that is GL4 rated. Some are both GL4 and GL5.

Eric_Phillips · Dec 29, 2008

DieselPower said:
You will find most (not all) gear oils these days are "yellow metal" friendly. Many you will find will have multiple API ratings, API GL-4 and GL-5 and MT-1.

This is contrary to what I have been told. How can I tell if the gear oil is yellow metal friendly or not? I have some Coastal 80W90 and it does not say anything about yellow metals. Do you know if this will work or do I need to take a trip to a NAPA store?

sld · Dec 29, 2008

GL5 by itself is not yellow metal friendly. GL4 is. Some are rated separately or together (safe for yellow) but stay away from something rated only GL5 if you have brass, tin or copper.

Eric_Phillips · Dec 29, 2008

So to confirm if it says GL-5, GL-4, GL-3 then is it yellow metal friendly.

RalphVa · Dec 30, 2008

I don't know about yellow metal. The Gravely I had used 10w30 engine oil in its transmission/differential area. Most front wheel drive cars use ATF (e.g. 5w oil) in the combined transmission/differential. My Benz uses ATF in its manual transmission. Even a 1965 Valiant used either ATF or gear oil in its transmission. I tried gear oil in it. Shifted way too hard. Put ATF in it.

Ralph