New with a temp. question!

[spoolinstyle]

Just picked up my 2000 6.5L Turbo (Diesel, of course) about a month or so ago and I am still new to all of this... so bear with me.

Tax refund came in first off.. woot!

I know I need a new T-Stat, since the one I has it stuck open I believe (no heat in the car, barely gets to operating temp)

My question to you.... would you rather opt for a higher temp T stat, or lower than stock? I figure, might as well try and do some sort of upgrade while I am fixing the issue.

Another question, would the motor perform better at a higher-then-stock temp, or a lower-than-stock temp? Sorry if I am rambling on with random questions.

[DmaxMaverick]

Lower temp stats are usually a band-aid for an underlying problem (and we all know, band-aids always come off at the wrong time). Issues with engine temperature have little to do with the actual operating temp, but with its ability to maintain/control temp. Often, on older vehicles, it takes some trial/error to determine your system's ability to maintain the temp (assuming all else is healthy). The engine should be operated at as hot as it can control the temp, ideally 190-210°F. Your engine has (or should have) 2 thermostats. The best performance I've seen (again, assuming all else is healthy) is using a staggered stat temp, 190° and 195°. This often provides a more gradual/progressive temp range. And, it is also important to use the correct stat style to get the most benefit (Heavy Duty Robert Shaw, or whatever they are calling it these days, www.kennedydiesel.com has them).

In most cases, when a 6.2/6.5 is overheating with OEM (195°) stats, and a lower temp stat helps, the problem isn't the stat, but a poorly performing cooling system (or other problem). In the end, the result will be a run-away ECT. Ideally, the cooling system should be able to maintain the optimal temp range and not overheat under extended full load use. Of course, there are exceptions and extreme conditions, but it should handle just about anything you can throw at it. If it is unable to maintain an ideal temp, something is wrong, or it is being abused (not that we would ever do that). Poor maintenance or ill-advised mod's are often causes of cooling issues. If your truck's service history is unknown or questionable (like if the stats are missing), you should consider a full cooling system service (drain, flush, core cleaning/rod and proper refill/bleed), as well as a test for head gasket condition (do this first).

And, to answer the question.... The engine is happier and more economical/efficient at a temp of about 195° (which just happens to be the OEM target ECT).