Pull yer plugs and snap some piccies of the business end. Post them up so we know what yer seeing. If one or more of the plugs are oil fouled...that's a good indicator that you have some bad oil leaks in the cylinder...
The plugs would be a good indicator of what cylinder(s) are burning the oil off. How many miles do you have on the engine? Did you put in any sort of additive during or before the oil change? Have you performed a leak down test or a compression test?
I'm surprised you didn't git a low oil indicator when yer engine used up 2 quarts of oil. Was the engine knocking at all? Are you positive yer not leaking the oil? Did you happened to over tighten the oil plug and it might have gotten stripped? Did you make sure the oil filter is on tight enough?
Usually coolant temp isn't a good indicator of low oil or oil burning.
What brand and oil weight did you put in? What brand of filter? Are you sure you filled the oil?