[Robby]

tdc?

Coolant flows freely through the heater core year round.....button positions open/close air doors allowing air to pass over the heater core.....the temp knob operates a mixer door that allows unheated air to bypass the core and mix with heated air that came through the core. Very little or no unheated air at max temp, and adding more unheated air as the knob is turned counterclockwise.

Rob

Rob

 

[Blue Angel]

What Rob said.

Early Cruze production were subject to a TSB to install insulation shielding the driver's right leg from the heat of circulating coolant. The lines to the heater core are right behind the trim and the heat was cooking people's legs in the summer even with the AC on.

 

[MetalMatty]

I never would have thought leaving it in gear while coming to a stop was more efficient. Same with letting the car warm up in the morning. Maybe it's because it's been below 10 degrees for the past month but it's an old habit. Guess I'll try and rid myself of it.

Also, I don't know if this has been brought up here or not (and I can't browse because I'm at work >.<) but in regards to using 89/91/93 octane to increase mileage... Is it actually beneficial? As in, is the extra 2-5MPG worth the extra cost of the fuel?

 

[obermd]

I never would have thought leaving it in gear while coming to a stop was more efficient. Same with letting the car warm up in the morning. Maybe it's because it's been below 10 degrees for the past month but it's an old habit. Guess I'll try and rid myself of it.

Also, I don't know if this has been brought up here or not (and I can't browse because I'm at work >.<) but in regards to using 89/91/93 octane to increase mileage... Is it actually beneficial? As in, is the extra 2-5MPG worth the extra cost of the fuel?

The MPG boost is real. You have to do the cost/mile calculation for yourself to find the sweet spot.

 

[obermd]

I have experienced better MPG in a number of N/A vehicles on higher octanes, particularly during hot weather, and fully expect to do so with my most recently acquired LTZ turbo. The less often an engine management system spends detuning the higher should be efficiency, with the proof of which often borne out at the pump.

The Cruze LS with it's 1.8 NA engine is this way as well.

 

[jblackburn]

89/91/93 octane to increase mileage... Is it actually beneficial? As in, is the extra 2-5MPG worth the extra cost of the fuel?

In my case, no, but I don't like how my car responds on regular in warmer weather.

Regular was $3.17 the other day. Mid-grade was $3.69 and Premium is $3.83. Ridiculous, right? The price gaps are less in other areas, but I usually figure in 50-60 cents/gal for 93 here. If I can get away with it, I just run 89 in all warmer weather but the peak of summer.

In winter, when my car runs fine on 87, I'll take the (maybe?) 2-3 MPG loss and cheaper fuel because it still saves me $. It's up to you to sit down and do the cost calculation...in an area with a 10-20 cent gap between grades, you'll probably save $ running on 89-93.

That said, your driving habits alone are the biggest impact on MPG and $ saved that you'll see at the pump.

 

[Blue Angel]

That said, your driving habits alone are the biggest impact on MPG and $ saved that you'll see at the pump.

Expanding on this a little for everyone's knowledge, my personal experience is that I don't see an increase in mileage with higher octane fuel, but let me explain why...

The harder you drive a car, the more load you put on the engine and the higher the combustion pressures are (more pressure = more torque). Demanding more torque from an engine means it's more likely to knock on lower grade fuel, which means the engine will pull timing to keep the knock in check. When the engine pulls timing it loses efficiency.

This all means that a lead-foot driver that spends most of their time driving in the city constantly accelerating, or doing 80+MPH on the freeway all the time, will gain the most mileage from higher octane fuel.

In my case, I drive easier than your Grandma and my commute is mostly low speeds with the cruise control set. I simply don't load the engine enough that it's running inefficiently even on 87 octane.

My persoanl reason for choosing higher octane fuel is the car runs much smoother, especially at lower engine speeds where I'm constantly lugging the engine up inclines in 6th gear. The extra few bucks on a fill is worth it for the smooth running... $0.16/L on a 40L fill is $6.40. Over the course of a two week tank of fuel, not significant for me anyway.

Part of my brain still believes that I'm getting slightly better fuel economy with higher octane since it allows me to use taller gears and lug the engine down farther, even if the savings are not significant enough to be evident in tank to tank fill up calculations. Since I can't back that up with hard numbers, it's just a hunch.

 

[obermd]

My persoanl reason for choosing higher octane fuel is the car runs much smoother, especially at lower engine speeds where I'm constantly lugging the engine up inclines in 6th gear. The extra few bucks on a fill is worth it for the smooth running... $0.16/L on a 40L fill is $6.40. Over the course of a two week tank of fuel, not significant for me anyway.

Part of my brain still believes that I'm getting slightly better fuel economy with higher octane since it allows me to use taller gears and lug the engine down farther, even if the savings are not significant enough to be evident in tank to tank fill up calculations. Since I can't back that up with hard numbers, it's just a hunch.

I have the experience to back your hunch. Anytime the car switches to the low octane timing maps it will throw away horsepower to protect the engine, which translates into requiring higher shift points to continue accelerating after you shift. This is true for both the 1.8 NA and the 1.4T engines in the Cruze. I have tested both of these engines on 85, 87, 89, and 91 and these cars, with the stock OEM plugs, require 89 or higher to have a fighting chance of staying with the high octane timing map. Both Penguin LS (2012 LS MT) and my 2012 ECO MT require shift points as much as 500 RPM higher when running on lower octane gas. This is a significant difference. Copper plugs allow me to run my ECO MT one octane level lower than on the OEM plugs, but the results still hold.

As you stated, running entirely highway miles at moderate speeds (2000 RPM or lower) will show no difference between octane ratings (this is why CruzeEcoBlueTopaz can run 87 and get 50 MPG), but as soon as you hit stop & go driving situations the higher octane will make a difference by allowing you to shift sooner.

The only real question is will you save money by running higher octane. The answer depends on whether or not you get enough extra fuel economy to cover the extra cost at the pump. For most people I think they will break even if the higher octane is no more than 25 cents a gallon (US). This means that 89 may very well be the best octane for most people because they will get the benefit of using the high octane map for most driving situations but only pay a marginal (10-15 cent per gallon) price premium.

 

[Blue12Cruze]

Just a quick question....would using 93 octane fuel from a top tier fuel retailer be beneficial for my '12 Cruze 6M?

 

[obermd]

Just a quick question....would using 93 octane fuel from a top tier fuel retailer be beneficial for my '12 Cruze 6M?

Yes. The question is will the benefit outweigh the cost. What you're looking for is the lowest octane that will allow your car to accelerate in your normal driving without you feeling any throttle pulsing. Any higher and you're wasting your money. In steady speed driving there is very little load on the engine and a lower octane will work. Under acceleration your engine is working hard and throttle pulsing is a sign of incomplete and/or poorly timed fuel burn. Either way you are throwing away horsepower, resulting in lower fuel economy and performance.

 

[Blue12Cruze]

Yes. The question is will the benefit outweigh the cost. What you're looking for is the lowest octane that will allow your car to accelerate in your normal driving without you feeling any throttle pulsing. Any higher and you're wasting your money. In steady speed driving there is very little load on the engine and a lower octane will work. Under acceleration your engine is working hard and throttle pulsing is a sign of incomplete and/or poorly timed fuel burn. Either way you are throwing away horsepower, resulting in lower fuel economy and performance.

Ok, with that being said, would using 89 (plus) octane fuel be most beneficial for my Cruze, or, should I just stick with using the 87 octane?

 

[jblackburn]

Ok, with that being said, would using 89 (plus) octane fuel be most beneficial for my Cruze, or, should I just stick with using the 87 octane?

I find perfectly acceptable performance in most weather with 89 octane in my car, with no need to jump to 93.

Is that a LS or LT in your sig? Looks like an LS...regardless, try a tank of 89, 93, and 87, and see what your OWN impressions are.

 

[Blue12Cruze]

I find perfectly acceptable performance in most weather with 89 octane in my car, with no need to jump to 93.

Is that a LS or LT in your sig? Looks like an LS...regardless, try a tank of 89, 93, and 87, and see what your OWN impressions are.

Yes, it is an LS 6M...I really don't want to use the 93 octane fuel if I don't need to, but, I've been experiencing decent power/acceleration in my Cruze with the 89 octane, so, I'm going to keep using the 89 octane fuel for the time being. And, I'm going to use the 89 in my cross-country move back to Arizona & see how the car performs at freeway speeds with the 89 fuel.

 

[06mistreSS]

Nice read and very good information, thanks for taking the time to do this write-up.

 

[Josh4291]

So just a quick question when it come to higher gases.

If 80% of my travel is highway going 60-75mph, what octane fuel should I use in my 2LT 1.4t?

 

[jblackburn]

So just a quick question when it come to higher gases.

If 80% of my travel is highway going 60-75mph, what octane fuel should I use in my 2LT 1.4t?

Whatever makes your car not surge or not lag on passes/uphill. Give midgrade a shot; if it seems like it's missing power, use 93.

 

[Josh4291]

I will try it on my next fill up, and keep everyone posted.

 

[nick993]

2013 2LT AT

In city my dic instant was claiming 35 at most at around 50 mph drive. Pump calcs show 29 mpg. Went CA 91 octane, new ngk plugs gapped to .034, tires pumped up to 44 psi and the resonator removed. According to the dic I'm getting 43 mpg easy on the same drive. Will post pump calcs after this tank. But my car feels great all thanks to the info on this site!


Sent from AutoGuide.com Free App

 

[Josh4291]

So if you aren't stomping the gas everywhere you go or doing 75-80+ on the highway 91 is a waste of money?

my last fill up was on 91 and I drive 100 miles a day usually running 55-70mph for 70% of the drive does that constitute running 91?

 

[obermd]

So if you aren't stomping the gas everywhere you go or doing 75-80+ on the highway 91 is a waste of money?

my last fill up was on 91 and I drive 100 miles a day usually running 55-70mph for 70% of the drive does that constitute running 91?

In the summer heat 91 is still worth it. Simply accelerating will put significant load on the engine, especially once you throw in the A/C and high external temperatures. If you feel pulsing in the throttle under any load you are wasting gas because the car is protecting itself from engine knock. Boost your octane from 87 to 89 and try again or 89 to 91. The engine in the Cruze is actually designed for 91 octane.