Whining Noise - 97 Avalon when Accelerating

It's a 97 Avalon and after an oil change at 152,000km - it seems to make a whining noise when acceleration or putting some throttle above 2000rpm, is this usually normal, it goes away most of the time. It just showed up 2-4days ago after the oil change. :rolleyes:

Check your belts, maybe some oil or slickness from old age.

My 93 camry has been doing the same thing. It slowly developed at about 150,000 miles, and it is still doing it now, at nearly 200,000. I cant figure it out, although it doesn't seem to be hurting anything. Transmissions will sometimes whine if the fluid is having trouble getting through the filter. You could try changing that, it couldnt hurt!
Did it start after the oil change? Could be spilled oil on belts, as csaaxon said above.