been researching the 180* stat more and cannot find a valid reason to not run it. the sludge argument does not appear to hold water as sludge formations occur at high oil temps that cause oil oxidation. that combined with oxygen forms sludge. still planning to find a 190* solution that will work.

2 reasons for seeking lower CTs, 1 valve seats & 2 head gaskets. head gaskets appear to be a metal one, and appear fresh. no idea if anything was done to the heads so assumption is they are still oem.

 

The main reason for running the higher temperature is better fuel economy. There may be an emissions component to it as well. The main reason for not running a cooler thermostat is the computer is programmed for higher temps. Run a cooler stat without programming for it, and your fuel economy goes to crap and you may get driveability problems. As long as you program the computer to run with the cooler thermostat there should be no problems, at least until winter comes around. If you live in a colder climate, the heater may not get hot enough with a cooler thermostat. That's vehicle-dependent though.

That being said, I've never felt there is any need to run a cooler thermostat on a street vehicle. When I've tried it in the past, fuel efficiency drops and the heater doesn't work as well in the winter. While there may be a power increase on an actual dyno, I've never noticed any increases on the 'ol butt dyno. And, I am able to reprogram for the cooler thermostat.

 

I agree 180 is going to hurt mpg's and heat will suffer in the cab, I think the 190* stat is the compromise I'd be happy with, just need to find the right solution for it. I have had no luck (last time I looked) in finding a stat that was close enough in the 190* spec to drop in there. The cummins one is a tad too big and would require it to be trimmed down some.

 

Main reason is ridding the engine of water..... yes, that stuff that constantly drips or blows out from the tailpipe. Water boils at 212* F. If you're constantly running below that, you'll retain much of the condensation in your engine. That's like constantly subjecting your car to the rigors of short trips, which are considered severe duty.

 

The OEMs don't care about whether or not water condenses inside the engine so long as it doesn't do it so fast that engine sludge can become a warranty issue. If the engine sludges up at 60-80K miles, they don't care. They absolutely do care about government mandated fuel economy. Engines are run around 200 degrees (195 thermostat) because it's more efficient. Run a cooler thermostat, and even if it's programmed for it it'll use more fuel to go the same distance.

Water in the exhaust comes from water condensing out as the pipes cool. And, it takes about an hour at highway speeds to fully purge condensed water from the crankcase.

 

Not to mention running a bit warmer also reduces emissions.... Something else the manufacturers are forced to care about.

 

a 5* drop in tstat temp is neglegeble for burning of engine condensation. i researched how sludge forms and one of the culprits is oxidized oil mixed with oxygen. the hotter the oil temp, the faster it oxidizes. full synthetic helps to reduce that process. i am confident the royal purple mixed with the stiction eliminator will control it internally. once i get that 190* in place, will see what can be done for the temp spikes i see when the motor sits. that is prob overkill but the valve seat drop issue is the concern.

 

Its been a year and last week the Dak got a new radiator and 180* t-stat. Engine runs at 188-190*f consistently, 186* off throttle, fan clutch in place, original e-fan in place.

200 miles on it since bringing it on-line again so the ECU relearn is still in progress.

I picked up another volvo fan to use on the Dak, planning to use a Hayden control kit I have on it using the low setting and remove the 2 oem's. The plan is to make a shroud to bolt to the oem e-fan points and look at using a different overflow bottle and wiper bottle. Will have to figure that out.

 

Filled up today... 1st tank with 180* stat. All hiway to work speeds kept in the 60-65 mph range, ambient temps in the 29-38* range IATs in the 60's (iirc) and CTs in the 188-190* range.

Mpg = 18.20x mpg <- A new personal best for me in this truck. previous was 17.9x in the summer months.

 

Update... Dak had taken a back seat to the Ram and only used around town. MPG's around town were 12ish at best, probably because of the heavy right foot. earlier this week the Rams clutch or trans bit it and is now presenting a metal on metal noise in 1st & 2nd gears so its parked until its fixed. That put me back in the dak and am now commuting in it for the foreseeable future (I expect the truck to be down at least a month while I line up a rebuilt trans & get a new clutch, 489K on it :-) ).

So as of now the Dak fuel used (gauge) vs miles driven (off by 10.7% for tires) is looking pretty good. Gauge wise it is sitting half way between the 1/2 & 3/4 marks on the gauge, miles is 180+ (iirc).... that is an eye opener as I did not expect that performance so far. Weather wise it has been raining every day so conditions suck. Certainly not good for mpg's. Cruising into work and up the ~2 mile grade 300' climb(?) I noticed I'm able to accelerate slightly without a trans downshift. I think I reported that previously so not sure if that is an improvement with the 180* stat.

What brought me back here is to share some interesting info I found on the Ram and am going to attempt to apply to the Dak. have a look at this post (& thread) Cheap performance bump Going to see if I can make a turning vane and install it in the Airaid intake tube I have. On the ram what I found was using the stock intake tube with the lower turning vane tested against the AFE torque tube & older stock tube w/o the turning vane proved to give me a good bump in bottom end torque. Very noticeable and based off of years of experience with my truck, felt like an approx 30hp/40~50tq bump. I say this because that was the same type of SOTP feel with a tuner that gave a 30/60 bump with just timing changes (remember Ram is a diesel). Shocked by this I got motivated to get my hands on a 2nd vane and try it in the upper hose. Once installed there was a further bump in performance but not quite as big as the 1st change. I was pretty shocked by it. Air box has the not so cheap air box mod V4.1 (boost controlled exhaust dump with a velocity stack on it) which also helped that performance bump. Drawback was after the changes mpg's dropped. Had to re-tune it to get mpg's back.

edit: What I forgot to mention is the vane is reducing the high pressure area of the tighter bends in the intake tube. On the Ram since it is a turbo and does not have a throttle body, flow into the compressor wheel is unrestricted.

Not sure what to expect with the vane install on the Airaid tube but am willing to experiment and find out. I will report back once I know in a new thread.