[TDIwyse]

I've been considering replacing my thermostat for awhile now, but not sure it's worth it. If the coolant temp wasn't getting above ~170 I'd probably do it right away to avoid some potential issues like excess engine wear. But I kinda like the 175-180F range.

http://www.carnut.com/ramblin/cool3.html

Also a corresponding reference regarding engine wear vs coolant temp.

https://books.google.com/books?id=q9...rature&f=false

Interestingly, the analysis on the 1.8 turbo direct injection diesel shows little impact to unburned hydrocarbons and particulate matter over most of its operating range with a wide range of coolant temps.

I also went and plotted the 5+ year mpg trend on my vehicle. It's kind of interesting. You can definitely see the winter vs summer undulations...

[335dwanted]

Just a quick update from OP: my temps remain in the low to mid 190's (did not really expect any changes to that). Recall that my temps before replacement were in the mid 170's, so the new thermostat increased coolant temps by 20 degrees F. We have not had any real low weather temps here in NJ so far so it will be interesting to see how the temps read in really cold weather. A couple of weeks ago I blocked off the upper radiators but not the lower and I have to say I can't see any difference; the terminal temp range has not changed and interestingly the time to warm up does not appear to have changed. Once we get into really cold weather I may take the covers out and see if there is any difference.

As for fuel economy, any changes are below my threshold of detection. I did not keep any records of fuel economy before or after. I do reset the trip and hand calculate with every fill up. I generally average between 28 and 29 MPG (roughly 40% HWY and my average speed on the computer is usually under 40 as I reset that every fill up as well).

[DWR]

Lubricants take a big hit in acidic environments. There is some research being done on basic filters that 'rejuvenate' oils. Also, soot has an unintuitive effect of reducing friction while increasing wear. Soot formation can increase at lower temps and load.

[TDIwyse]

Originally Posted by DWR

Lubricants take a big hit in acidic environments. There is some research being done on basic filters that 'rejuvenate' oils. Also, soot has an unintuitive effect of reducing friction while increasing wear. Soot formation can increase at lower temps and load.

Agreed. One of the reasons I've been doing UOA's since early on. Was useful for checking on these concerns as well as the water/methanol usage, biodiesel usage (fuel dilution concerns), etc.

But again, haven't seen any negative issues with operating at coolant temps from 175-180F in my unit.

2 of the latest UOA's can be seen here: http://www.e90post.com/forums/showpo...6&postcount=25

[daytonadave]

Hi folks. 2011 335d msport. 60k & just cleaned the carbon out. A question regarding the thermostat, is there a 200 degree unit available ? Or, do I have to fab something ? Thanks, I don't mean to hijack the thread.

[BB_cuda]

Not a high jack in my book. As far as I know, standard is 88C (~190F). Curious what you do to a T/S to make it open at higher temp? Short of using louvers on the radiator (ala Cruz eco).

Truck I own has a 203F. Not sure if changing out guts of it would work in the BMW housing (and if it's even feasible).

[DWR]

Originally Posted by TDIwyse

Agreed. One of the reasons I've been doing UOA's since early on. Was useful for checking on these concerns as well as the water/methanol usage, biodiesel usage (fuel dilution concerns), etc.

But again, haven't seen any negative issues with operating at coolant temps from 175-180F in my unit.

2 of the latest UOA's can be seen here: http://www.e90post.com/forums/showpo...6&postcount=25

Just wondering how you estimate the hours of operation? Are you using OBD data?

[BB_cuda]

Hours is miles on those UOAs. When you click his link to other thread, it explains this in very first sentence.

[locolobo]

I replaced mine a couple years ago after noticing it was running 80C. EGR is blocked. Even with the new part, it has improved but still almost always running below 88C even on the highway.