So some good and not so good info in this thread.
Basically, the Apache we have uses a TADS FLIR based on a SADA II detector, i.e. a 2nd gen flir that operates in the LWIR region. The main issues here are less so about resolution, but rather sensitivity as Gen2 FLIR's were still scanning based detectors which for all intents and purposes reduces the sensitivity of the detector as its rastered across the FOV which basically reduces the sensitivity as the "dwell" time per pixel is much less than what you would get than with a more modern 3rd gen "staring" array. This version of the tads has 192000 detector elements array in 4 columns outputting 960 lines of video, but its downsampled for the actual video feed by a bit "because TV signal reasons".
At any rate, too many people tend to think of FLIR as magic predator vision as it is, but the general points that have been brought up are generally valid, moving/running/working vehicles will tend to be "warm" while non-running vehicles will tend to be "cool". Also remember that a ton of work has gone into making vehicles less detectable by sensors such as FLIR and most military paints are designed to be non-reflective and less emissive in those specific bands. And for any given FLIR image you are looking for a signal that is a combination of emissivity and reflectivity. The other thing to remember is that all signals get reduced with range (that highly scientific R^2) relationship that tends to apply to most things. Moreover environmental conditions such as humidity/clouds/rain heavily absorb and scatter IR signals, so range should further be reduced in those scenarios. And also realize that IR signals from the background are going vary very widely between day and night and inbetween i.e. the dirunal cycle and thermal crossover times.
At any rate the bigger issues with the ED FLIR implementation tend not to be in the actual vehicle stuff they have modeled, rather issues with things like what the actual background images should look like at various times of day and the further fact, while the TADS operates in the LWIR as well as a few other systems, the main TGP's on aircraft operate in a totally different IR band MWIR, and will look different, especially during the day due to the fact MWIR is more effected by IR reflections than LWIR. But I'm not sure ED is actually planning to model any actual differences in sensors as nothing to that effect has been discussed officially.