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yzeffer
Dodge Dakota
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11/15/2005
16:56:41
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 Subject: 180 degree thermostat-MPG down?
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I just installed a 180 degree thermostat in my 2001 Dakota CC 3.9 4x4. I get between 17.5 to 18 MPG, now that I have installed this 180 degree thermostat I just filled my tank and I am now getting 16 MPG. I have a slight ping in my engine and I figured that might help a lil but im not gonna sacrafice that much to help that problem out slightly. Does that thermostat make the engine that much richer?
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GB2000
GenIII
11/15/2005
18:10:53
| RE: 180 degree thermostat-MPG down?
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Many have noticed a 1-2mpg drop
Josh Blackshire - Founder, OhioDakotas.NET
Red 98 Dakota Sport - Check it out!
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Adam
Dodge Dakota
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11/15/2005
18:47:25
| RE: 180 degree thermostat-MPG down?
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Yea I'm thinkin I have the same prob... was getting around 16.5-17.5 and now I get a steady 15.5
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schmidtmike
Dodge Dakota
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11/15/2005
18:53:35
| RE: 180 degree thermostat-MPG down?
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Yes, heat is the enemy of a gasoline engine, but
heat is also efficiency. Your ECT (engine coolant temperature) sensor will put more fuel into your engine when it senses a decrease in temperature. The computer likes to see 195-205 degrees at normal operating temperature. With a 180 or 160 degree thermostat, it thinks your engine is too cold, and puts more fuel in to warm it up, but because the T-Stat is opening sooner, the heat created by the excess fuel burning gets carried away the cooling system, defeatting the purpose of adding more fuel.
In short, adding a low degree thermostat to a computer-controlled vehicle is just about the worst thing you could do to it. Any horsepower gains will be marginal, and not enough to justify the 1-4 mpg loss. Also, because the engine is using more fuel, more unburned fuel is going to the catylitic converter, which can overheat it,
possibly melting the honeycomb catylist inside.
Plus, when an engine runs cooler than normal, the process of oil sludging speeds up. It is known that sludge forms because of water(condensation), acids from blow-by, and oil combining, creating sludge. Sludge forms better when engine temps are lower (i.e. low T-Stat, no T-Stat). Engines need to reach normal operating temperature in order to burn off condensation from inside the engine, and yes, gaskets and metals are more than capable of handling 200+ degrees of continuous temperature (i.e. Northstar V8 runs from 210-230 degrees).
My recommendation, switch back to the factory T-Stat. You're only hurting your car, not helping it.
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Adam
Dodge Dakota
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11/15/2005
19:34:38
| RE: 180 degree thermostat-MPG down?
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Yea I just went and bought a new 195 t-stat after I posted that. I think i threw my old one away becasue I'm retarted...that or I did a good job hiding it from my self. Hope this'll bring mileage back up... if not at least it'll warm up a little quicker being that it's getting damn cold here.
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daddio
Dodge Dakota
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11/15/2005
19:41:31
| RE: 180 degree thermostat-MPG down?
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i had the same results in my '00 QC 3.9 & no performance gain. reinstalled the 195 and run without the clutch fan. my temp gage never gets to 210 which is dead center.
if pinging is a problem try a spark plug 1 range colder than stock. if that doesn't work try using some seafoam poured down the tb as per the directions on the bottle. carbon buildup in the combustion chambers will raise compression and insulate the chamber from the cooling system and make it tend to run hotter.
if those 2 things don't help you may have a bad plenum gskt.
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Gregg
Dodge Dakota
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11/15/2005
20:36:42
| RE: 180 degree thermostat-MPG down?
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schmidtmike nailed it a few posts back. He absolutely defined the effects of a cooler T-stat. I have to point out however; real world results may differ from theory.
Cooler running temp tricks the computer into a richer mixture. This reduces ping and MPG. I own a '99 cc 4X4 and she pinged with 87 octane like a kid whackin' a garbage can lid. Reading this very site I went shotgun on it. Slapped in the 180 T-stat, NAPA brass cap-n-rotor, Seafoam de-carbon assault and the magic Autolite plugs. Instant fix!
It has good pull, no ping unless summer heat under load where I switch to mid-grade fuel for the cure. Considering the pain it is to swap the stat back out, I'll eat the slight mileage loss and put my foot into it with confidence I'm not gonna detonate my engine.
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yzeffer
Dodge Dakota
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11/15/2005
22:13:52
| RE: 180 degree thermostat-MPG down?
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Message:
Thanks for all the replys. Since its easy to get at and Im trying to get the best gas milage possible from a dakota I will be switching it back tomorrow. Next on my list is the brass cap and rotor and some new plug wires and new plugs one step cooler. Already did the seafoam treatment...
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Adam
Dodge Dakota
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11/15/2005
23:24:56
| RE: 180 degree thermostat-MPG down?
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Ok I've changed the T-Stat out so hopefully things go back to the way they were...what's the difference when going to a cooler range plug?
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GB2000
GenIII
11/16/2005
00:58:35
| RE: 180 degree thermostat-MPG down?
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Usually not a real noticeable difference...might notice a smoother idle or your truck may run like sh!t. Some don't take well to cooler plugs and will run worse.
Also...I don't recall who posted this or anything but somebody posted a while back (may have been Larry...but I'm honestly not sure) about how even DC has admitted that our engines run more efficiently at around 182 degrees I think and that the 180*F thermostat won't hurt it at all...however the 195*F is used for emissions and gas mileage purposes. If that's true...I'm willing to eat the 1-2 mpg drop as well.
Josh Blackshire - Founder, OhioDakotas.NET
Red 98 Dakota Sport - Check it out!
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GB2000
GenIII
11/16/2005
01:10:25
| RE: 180 degree thermostat-MPG down?
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Message:
Okay...found the post after much searching...
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Jake
Dodge Dakota
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6/22/2005
13:51:19
RE: 180 TS, Why?
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Mopar engineers and motorheads,in the case of the 3.9, discovered the motor will make better power around 180 degrees than 190+. A 165 is too cold for the engine to make its best power by keeping the head temp too low. A 165 may not cool as well as a 180 since there is less residual coolant time in the radiator meanng the coolant moves through the radiator too soon(and fast)and cannot dissipate the heat. Remember, a thermostat is not either open or closed, but varies the amount of circulation depending on the coolant temperature. Selecting the correct thermostat helps retain cylinder head temperature making better power without over cooking things. Naturally, air temp plays a big part in cooling, so installing the correct thermostat for the type of climate in your area is important. In our case, a 180 on the average will do the job.
During the summer months, I use a 180, but in the winter, I switch to the 192. Temps will vary from the high 90s in summer to 0 in the winter.
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http://www.dodgedakota.net/boards/v6/12176.html
Josh Blackshire - Founder, OhioDakotas.NET
Red 98 Dakota Sport - Check it out!
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zzark
Dodge Dakota
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11/16/2005
01:30:17
| RE: 180 degree thermostat-MPG down?
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Message:
So what we need is a 187 degree t-stat !
zzark
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stevebdak
Dodge Dakota
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11/16/2005
12:02:59
| RE: 180 degree thermostat-MPG down?
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I had the same drop in MPG with my 97 Dakota V6 when I went to a 180 degree TSTAT. To get the MPG back, I went with a Jet stage II chip. I went from a 1 MPG loss to a 3 MPG gain. Yes I did go from regular to mid grade. Other than good MPG, the Jet Chips don't seam to do much. I got mine used and at a cheap price.
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GB2000
GenIII
11/16/2005
12:21:28
| RE: 180 degree thermostat-MPG down?
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Message:
zzark...actually, yeah, that's prolly what we need. lol
Josh Blackshire - Founder, OhioDakotas.NET
Red 98 Dakota Sport - Check it out!
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95V6
GenII
11/16/2005
12:39:55
| RE: 180 degree thermostat-MPG down?
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same experience as stevebdak. Got better mileage with 180 tstat and jet II.
95 3.9L 4WD V6, K&N, Gibson exh, JBA hdrs, JET stage II, MSD 6A, Rancho shocks and more..
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schmidtmike
Dodge Dakota
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11/18/2005
14:42:28
| RE: 180 degree thermostat-MPG down?
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Message:
GB2000, you do make valid points. But remember, proper stoichiometric A/F ratio is 14.7:1. With more fuel going into the cylinder, it is doing nothing but richening the air/fuel mixture. If the same amount of air is going into the cylinder, more fuel will not produce more power. For every one pound of fuel burned, the average engine needs to mix it with 900 pounds of air. If more air is introduced, more oxygen will be available, allowing the introduction of more fuel into the cylinders. So, without the necessary flow improvements to allow more air in, the lower degree thermostat will not produce ANY more horsepower, and only lower fuel economy.
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bluedak98
Dodge Dakota
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11/18/2005
15:12:05
| RE: 180 degree thermostat-MPG down?
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Actually, maximum power is not made at a stoich A/F ratio, but slightly rich. Maybe if an engine would burn 100% of the fuel introduced, 14.7:1 would produce max power. Ideally, we would be able to adjust our fule maps to be lean at part throttle conditions and slightly rich at WOT to save gas and produce max power.
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davidjn86
Dodge Dakota
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8/16/2012
18:09:05
| RE: 180 degree thermostat-MPG down?
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Message:
what if you live in the las vegas were it get to 115 degrees in the
summer would the t-stat good idea then ?
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