So long as the bottles were in a cool, dry place and unopened, there are chances it's just fine to use. I've been told that the parts of the bottle unfilled with oil are an inert gas such as nitrogen. It greatly increases the shelf-life as it will prevent oxidation. Once the bottles become unsealed, the nitrogen has likely made its way out, and the oxygen introduced from the bottle from the atmosphere is free to react with the oil. Just make sure you shake it up a little, and that it looks, flows, and smells fine.
Not sure where this guy got his info, but I would believe in what he's saying. (Given this is in regard to motor oil, but I believe the same principles apply.):
http://wiki.answers.com/Q/Does_motor_oil_have_a_shelf_life
Originally Posted By: "wiki answers"
It appears from my limited research that it depends how it is stored, not too hot and not too cold it will be okay for years if it is in the original sealed container.
Some companies will only guarantee it for two to five years on the shelf but others the web say that if it is shook well to remix the additives in the bottle then they haven't any problems.
Don't store it any other container and don't leave open to air as it oxydizes. Opened bottles will deteriorate much quicker.
Motor oil does have a shelf life. Depending on whether it is synthetic or conventional, it can be stored from any time of two - five years.
I had an unopened plastic container of gear oil (SAE 80 ie thick) and over a number of years the container started to collapse, suggesting that the oil was reacting with the plastic or, more likely, that some more volatile or smaller molecular particles had passed through the container walls reducing the pressure inside. Thus I would suggest that the oil properties changed over time, probably for the worse. The shelf life of oil will, in addition to temperature, temperature change, humidity depend on the container that it is in and its make up (what kind of oil it is )
There's also the end of this page in regards to storage of engine oils:
http://www.carbibles.com/engineoil_bible.html
Originally Posted By: "engine oil bible"
Technically, engine oils have shelf lives of four to five years. However, as years pass, unused engine oils can become obsolete and fail to meet the technical requirements of current engines. The specs get updated regularly based on new scientific testing procedures and engine requirements. But this is only really a concern if you've bought a brand new car but have engine oil you bought for the previous car. An oil that is a number of years old might not be formulated to meet the requirements set for your newer engine.
If your unopened containers of engine oil are more than three years old, read the labels to make sure they meet the latest industry standards. If they do meet the current standards, you might want to take the extra precaution of obtaining oil analysis before using them. An oil analysis will check for key properties of the oil and ensure that it still meets the original manufacturing specs. Of course the cost of getting an analysis done on old oil is probably going to outweigh going and buying fresh stuff. So it's a double-edged sword.
As a general rule, the simpler the oil formulation, the longer the shelf life. The following is a guideline under protected conditions - indoors at about 20°C:
Product Shelf Life
Base Oils, Process Oils - 3 years
Hydraulic Oils, Compressor Oils, General Purpose Lubricating Oils - 2 years
Engine Oils and Transmission Oils - 3 years
Industrial and Automotive Gear Oils - 2 years
Metal Working and Cutting Oils - 1 year
The following are signs of storage instability in a lubricant:
* Settling out of the additives as a gel or sticky liquid
* Floc or haze
* Precipitates/solid material
* Colour change or haziness
Water contamination in a lubricant can be detected by a "milky" appearance of the product.
Good luck!
, thanks !