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Last week Idaho set record highs at 110F two days in a row. I do not use my a/c at all I suffer and sweat it out by rolling down the windows and using gel ice packs. Yes I know im crazy but I will tough it out this summer just as a did last summer. I would rather reduce the engine load and keep my MPG up. Because there is a noticable decrease in instant mpg by about 10-15 with the a/c on even at highway speeds. Some might argue rolling the windows down increases drag and reduces mpg but I have not seen any noticable decrease on the instant mpg from rolling the window down. I have tried using the a/c and at the end of the day driving 375 miles my mpg is reduced from 58 on the DIC to 49.
Regarding the engine fan as I was saying up until about 2 weeks ago I have never caught my coolant temp below about 215F which leads me to believe the fan has never turned on all year well up until about 2 weeks ago when I noticed my coolant temp at 205 F while cruising on the highway in 100F heat. I only know of 1 speed for the fan on and off but I could be wrong.
Some cruze owners have even reported the engine fan starting and staying on while the car is started with the hood open. Yeah mine doesnt do that. Im not complaining about the fan at all the car does a great job at staying cool and at normal operating temperatures. Im just curious about when and how the computer decides to use it. If it depends on the air intake temp from outside or the coolant temp.
If the fan is electric and it doesnt have any impact on the engines efficiency and it does such a great job at keeping the coolant temp 10-15 degrees lower why isnt it always running ?
I also would like to note I have been running 91 octane fuel the past 4 weeks during this extreme heat and my avg MPG for the month after driving more then 7,500 miles was at 51.6 up 1mpg from this time last year. That is mainly a result of me slowing down on average about 6mph and due to better weather conditions such as warmer temperatures and much less wind.
Plain and simple each day I do about 375 miles and on an average day will consume 7 to 7.2 gallons regardless of which octane im using wether its 91 or 87. I hate to say it I just dont see a noticable increase not even 1mpg more using 91. In fact im going to switch back to 87 non ethanol for the month of July and I guarantee my monthly mpg avg is going to be about 52mpg which will be about a 1/2 mpg increase from last month using 91 with both months being exactly the same weather conditions, speed and route.
Im in sort of a delimmea here I would prefer to use 91 top tier non ethanol but its not available to me only 91 top tier is which is what I have been using the past month. Now the past year I have been using 87 top tier non ethanol which has been fine except im concerned about engine damage from low octane fuel. If this isnt an issue and in fact 87 octane is perfectly fine and harmless for the engine I will continue to use it because for me non ethanol and top tier are more of a priority for me then octane.
Coolant temps run high for emissions purposes. I suspect it reduces temps by running the fan and regulating the thermostat when it detects knock (from high outside temps pre-igniting fuel) often.
2 fan speeds - low speed as for the AC and then JET PLANE (usually happens when the thermostat or water pump goes bad. Or in my place, an expansion valve driving the high side AC pressure past 450 psi).
My comfort > MPG. Forget that 110 degree crap. I've also noticed that I tend to shift a lot higher with the AC on to make up for the sapped power, so I imagine mine will take a real nosedive now that it's going to stay hot outside. 93 makes a huge difference when running the AC. It was fine on lower octane (87/89) without it.
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Last edited by jblackburn; 07-08-2013 at 03:43 AM.
2012 Cruze 1LT 6M
Are you sure you not low on coolant.Sounds like the leaking water pump problem.
Stage 0 Vtuned 174HP/177TQ / Per GM Torque PID 174hp at 5527 rpm (165 lb-ft @ 5527 rpm), Peak 177TQ at 3500 rpm 19 PSI Boost. Latest Vtune 21 psi boost 178HP/201TQ / Per GM Torque PID
The Cruze has a radiator fan, an electrically manipulated thermostat, and the Eco adds to that the lower grille shutters. Your car has three methods of controlling coolant temperature.
I don't know 100% for sure with the Cruze, mostly just because I've never actually read it somewhere, but most if not all cars with electric fans do not operate them above a certain speed. They rely solely on airflow unless coolant temps get above the high speed fan setpoint temperature. I believe this is the case even when using AC, but I don't claim to know for sure with every car. I imagine at 60 MPH the Cruze never turns the fans on unless it detects an overheating condition.
That leaves the thermostat and the shutters.
The thermostat opens and reduces coolant temperature when the engine is under a certain amount of load. It's also possible that it opens when the ambient temps exceed a certain point. I think this is what you're seeing, not the fan operating.
The shutters are also temperature controlled and will open if the coolant temps dictate more airflow is required over the rad. I don't know anything specific about when it attempts to open and close, other than the GM PR info stating that it closes at speeds above 40 MPH and will open if needed for cooling. I'm pretty sure mine stays closed almost all the time in the winter since it was always closed when the car was parked.
Regarding AC, I avoid it as much as possible also and I don't buy into the nonsense that opening windows takes more power. I'm sure if you are driving with all of the windows fully down there would be a point where at some speed the drag would cause more loss than using the AC, but who needs to drive with ALL of the windows down fully at those speeds?
I crack both passenger side windows down about 3-4 inches and leave the driver's side glass up. This makes a nice rotating breeze in the car that creates minimal drag and still keeps me cool enough unless it's really hot out (or "she" is in the car complaining about the heat). Doing the pass side windows down all the way creates quite a breeze in the car and may be even more effective than having all the windows down, with less drag.
Keeping the driver's side windows up will also protect you from hearing loss associated with wind blowing in your ears at high speed for extended periods of time... you do a LOT of driving.
I have noticed that the engine fan never turns on for me unless its like at least 90 - 95F + degrees outside and when its 95 - 100F + outside its pretty much always on. And im not talking about while the a/c is on because I do not use it. I usually can tell when the engine fan is running because pretty much any other time of the year except the hot summer weeks my coolant temp is at 217F and when the fan is on its usually at 203F.
I totally agree with everything you just typed out BlueAngel
One thing I would also like to point out is that we have had 3 days in the past 2 weeks of extreme 110F + degree weather here in Idaho and I noticed on those days my fuel efficiency was slightly reduced. So it seems that extreme cold AND heat can have similar impacts on efficiency.
Last edited by CruzeEcoBlueTopaz; 07-11-2013 at 12:42 AM.
Ok. Don't mean to derail your thread CruzeEcoBlueTopaz.
I got my Cruze back today. It was a defective water pump that was leaking coolant. It caused the thermostat to go crazy. My temp gauge was always reading normal temps, yet the dealer said on their test drive they measured it at 273F (trifecta runs around 205F normally). Everything was covered under warranty. They told me that the radiator fan usually will not engage unless driver temp controls are active or temperatures are rather extreme on the hot side. The radiator fan now is back to normally and isn't on under normal driving.
CruzeEcoBlueTopaz - I understand you wanting to get better fuel economy but physics and mythbusters prove that over 50 mph lowering windows affects the aerodynamics of the car more than the additional load caused by A/C. The car doesn't use much energy at all on the highway as is so A/C won't make much difference. It makes sense to just be comfortable and not put your health at risk because you may not be saving any fuel at all. I believe there was a thread that said it takes only 10 HP to move a Cruze Eco at highway speed. Not much in the grand scheme of things.
Well thats great news. I bet you feel a bit of relief now knowing you have a new water pump doing its job and the fact that it was covered under warranty. I put my head in my engine with a flash light every weekend and check for leaks and oil and so far after 130k its still as chevy would say LIKE A ROCK.
Allright tomorrow im going to try it I will only use the a/c at highway speeds. Now if I understand correctly my efficiency will actually slightly increase because of the less drag on the car. Right now im getting between 51 and 52mpg daily. I will post friday what my mpg was for thursday.
Last edited by CruzeEcoBlueTopaz; 07-11-2013 at 01:03 AM.