Can two-cycle oil go bad? Quickly?
This is trippin' me out, and has me wondering if this bottle of oil I have is safe to use. Based on what I've read here and elsewhere about what's good to add to the fuel, I've been adding ashless marine two-cycle oil, PLUS Power Service white bottle, to every tank. I make a mix of 3 parts oil, 1 part PS, then add 1 oz of that mix per gallon of fuel.
I was just about to mix some more of that up, and here's what's weird. I wasn't sure if what I had in the two-cycle bottle already had the PS in it, or was just the oil. So I gave it a sniff test. And here's where it got weird; it smelled REALLLLLY strong of ammonia! WTF! Made me nervous about whether it was still good. It was a gallon bottle, about 5/8 full, cap on tightly, kept in a fairly cool dark basement, maybe 4-5 months old.
Just for grins, I sniffed some of the pre-mix stuff (made from the same base stock, same age), and didn't get any smell of ammonia, but could smell the PS. So I guessed the stuff in the big bottle was stuff I HADN'T mixed yet (straight 2-cycle oil). Hmm, maybe the stuff always smells like this, and when I mix it down, it'll smell like this earlier batch? Okay, maybe. So I made a little test batch; 6oz oil + 2oz PS, in an empty bottle. Smelled just like the old mix. Okay, this must just be something I missed; never noticed that two-cycle smells like ammonia, no big deal.
So I figure I'll just make a full batch of 3:1; there were about 72oz of oil in the bottle then, so I added 24oz of PS and gave it a shake. Just to double-check, I gave that mix a sniff, and dangit all, now I can really smell the ammonia again!
So now I'm wondering -- was this oil "spoiled" somehow? After being opened, did the exposure to the air cause it to form ammonia? Is it still safe to use? I'm thinkin' I just wasted a good part of a bottle of PS, putting it in that spoiled oil. But how the eff could that happen? This sound at all familiar to anyone?
Maybe I need to start buying the two-cycle oil by the quart bottle; dang, that's gonna cost more.