Ok, first of all im not saying that its anything to be worried about, but what rise in engine temp would concern you?

2000 TJ, bought it 8 months a go, before summer started... now over that period of time to now, the temp gauge has steadily increased 1.5 bars on the gauge, to now sit 1 bar below half way... now initially i thought that over summer, it was just because it was warm, but now the weather is cooling, the temp has remained the same... checked coolant levels, still good, oil level fine, atf fluid level good and colour fine. I did just replace the air filter which brought down engine temp a fraction (it was pretty clogged - work in a farming area, lots of dust)...

In the overall, general scheme of readings "on average" for a tj... is one bar below half way, normal?

Can a rise of 1.5 bars be easily attributed to the degredation of engine oil (now 20k old)? Plan to change soon and the filter...

And can a dirty engine (and bay) add to the temp? Because, when i bought it, it was very clean and def not so much now!!

Any thoughts appreciated! Thanks

A couple of bars either side of half way would be considered 'normal', and any reasonably rapid variance from where it normally sits would be considered 'abnormal'. A couple of bars either side isn't much to be concerned about unless it happens quickly, ie. in a few minutes. I don't think the gauges are calibrated particularly accurately, what's normal for one car may be a couple of bars different for another. If it's below half way you don't have a lot to worry about. A dirty engine bay is unlikely to make enough difference to be noticeable on the gauge, old oil could though as it won't be as slippery as it should be and friction will be higher. Do an oil change and see what happens, it needs one anyway.

Mine sits on halfway ....never goes past. Correct me if I'm wrong but I think halfway is normal.

Thanks for the replies, try to do oil and filter in the next week... might test the coolant to see if it needs replacing too, not sure what quality was put in last time and when exactly that was... might just be me, but it doesnt look as "luminous" green as usual, slightly darker... think it was about a year and a half a go it was last serviced...

both my tl's sit one notch below halfway

My TH always was 1 bar under halfway, but later in the process of working out an overheating problem (caused by failed thermofan) I removed the themostat, the TJ that replaced it had overheating which eventually I found was the thermostat - I put the one out of TH in the TJ and the TJ reads exactly Halfway - Ie the same thermostat improved a bar in a different car so I think if you are within 1 bar on the gauge you are "within spec".