Does oil go bad over time?

[Shotgun]

I noticed that the oil change sticker on my truck gives the mileage and date the oil needs to be changed. If I change the oil in my ATV, and then don't ride for 5 months, do I need to change the oil again?

[Toomey]

Not positive but I highly doubt it.  I'd probably change it just to start fresh after such a long time.  It's preety cheap, and I like the wrenching.

[53yfz450]

yeah your better off changing it. its cheap. also change your gas.

[Chevy1500z71]

yea if my bike sat for 5 months id probabyl change the oil and always change the filter with it there so cheap, y not. if you have a air filter and rode before you put it away for 5 months id clean that too.

[Fox17]

dont let your bike sit for 5 months! i would change the oil. and definately the gas!!!

[Old_School]

I love google:

"
  Posted Mon September 26 2005 02:40 PM 
According to leading oil analysis companies in the U.S., as well as a Technical Bulletin (#863)published by Mobil Oil, Oil itself does not "break down". The base oil will always remain the base oil. However, many factors cause an oil to become less and less efficient at lubricating.

According to the Mobil Oil Technical Bulletin #863, "Oil does not wear-out, break-down, or otherwise deteriorate to the point that it needs to be replaced. It does become contaminated with water, acids, carbon and sludge so that it can no longer provide the protection needed for high precision engine components."

Ultra-fine filtration (less than one micron) can substantially reduce the contaminates to a point where the oil is "better than new". However, there are factors that must be considered.

First, engine oil if formulated with many additives. There are additives to reduce foaming, clean the engine internals, modify the viscosity, and hold particulate. Using a sub-micron filter can remove (strip) any additive that is held "in suspension" (dispersed) from the oil, if it is larger than the micron rating of the filter. Any additive that is "in solution" (dissolved) in the oil will not be removed. According to Mobil, only the viscosity modifier is "in suspension" and able to be removed. But there is an exception. The dirt holding molecules in the oil can be removed after the dirt has begun to cling to these molecules. I will show why this is important in a moment.

Second, the filter must not only remove the particulate contamination, but also the moisture, oxides, acids and sludge to be the most effective. Without removing these contaminants, your engine will start to eat itself away from the inside.

Therefore, if you can continually filter the oil through a filter that is rated to less than one micron, remove the oxides, acid, sludge and moisture, you can effectively keep your oil at better than new specifications.

Used oil that is already dirty (called wasted), has been contaminated to the point that this technique will remove the beneficial additives right along with the contamination. So this whole process would need to be performed on equipment that has had a thorough cleaning and oil and filter change. This should allow you to use the oil indefinitely, only sampling for analysis. "
 

[Hoosier Daddy]

You know what bothers me? when we wait to pull oil out from the ground after a million years of it sitting there and we pulled it out one day late, now its bad.. sucks to throw out all that oil...