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Discussion Starter · #1 ·
I have a 2012 Eco M6, and drive 140 miles a day, usually 80-82 on the way to work, and 72-75 on the way home. Speed limit is 70 for 3/4 of the trip.

By some quick math, I can save about $50 a month by running 87 instead of 93. I only actually need 93 when it's hot out. I now run 87 in the winter, 89 in spring and fall, and 93 in summer.

A big intercooler, or alcohol injection should do it under boost, but in hot weather with 87, it will stumble real bad accelerating from a stop if you let the clutch out too fast.

So I'm thinking about freeing up the exhaust. Catless downpipes don't seem to be available anymore, and I'm not sure I'd want one anyway, as I don't think I want a tune, since I'm not looking for more power. Would a mid pipe, and/or cat back make much difference and allow me to run cheaper gas?

I've had an UltraGauge for a while, but just got Torque going today, so now I can see KR. It's like 15* and snowing out now, 87 seems fine in this weather.

What plugs and gap do I want? Most info I've found about plugs is about being modded/tuned/higher boost.
 

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I get better mileage running 91 octane over 85.

I get better mileage running 60 instead of 80.
I save a ton of money on insurance not getting a ticket.

My car is in stock form. It gets 42 mpg.
It doesn't use everyone's favorite brand of oil or gas.
 

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2015 Cruze 1.4L engine 6 speed AT
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Well, this thread could turn into a fire storm. :eek:
Ok, now that I have my asbestos undergarments on here I go.

For my car running 87 octane gives me the best miles-per-dollar, and most of the time it runs great. When the summer heat hits above about 95F I use 89 octane, because if I don't I'll usually have a bad idle and engine stumping at low speed. Using 91 octane will give me the best mpgs, but worse miles-per-dollar. And considering 89 octane has always been enough, I consider 91 octane a waste. I will say that the gen2 guys using 91 or 93 octane is legit to prevent LSPI damage while getting the best mpgs at the same time.

Would a mid pipe, and/or cat back make much difference and allow me to run cheaper gas?
I doubt it, lower exhaust back pressure isn't a guarantee for improvement.

I don't think I want a tune,
IMO Trifecta is the best option. Even though when I contacted them they had very little interest in making a MPG based tune. But the times are a changing. :ROFLMAO:

now I can see KR. It's like 15*
That is scary, last I looked I was at 0-1*
I'd look into de-carbing your engine.

What plugs and gap do I want?
AC Delco 41-121 Check/set gap to .028"

FWIW, installing the ZZP coil pack was a real upgrade for my car ignition. (y)
 

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Discussion Starter · #4 ·
Well, this thread could turn into a fire storm. :eek:
Ok, now that I have my asbestos undergarments on here I go.

For my car running 87 octane gives me the best miles-per-dollar, and most of the time it runs great. When the summer heat hits above about 95F I use 89 octane, because if I don't I'll usually have a bad idle and engine stumping at low speed. Using 91 octane will give me the best mpgs, but worse miles-per-dollar. And considering 89 octane has always been enough, I consider 91 octane a waste. I will say that the gen2 guys using 91 or 93 octane is legit to prevent LSPI damage while getting the best mpgs at the same time.


I doubt it, lower exhaust back pressure isn't a guarantee for improvement.


IMO Trifecta is the best option. Even though when I contacted them they had very little interest in making a MPG based tune. But the times are a changing. :ROFLMAO:



That is scary, last I looked I was at 0-1*
I'd look into de-carbing your engine.


AC Delco 41-121 Check/set gap to .028"

FWIW, installing the ZZP coil pack was a real upgrade for my car ignition. (y)
It's 15* Fahrenheit outside temperature. Not 15* of KR. I saw 1 to 1.5* of KR once or twice.

Thanks for the info on the plugs and coil pack 👍
 

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Discussion Starter · #5 ·
I get better mileage running 91 octane over 85.

I get better mileage running 60 instead of 80.
I save a ton of money on insurance not getting a ticket.

My car is in stock form. It gets 42 mpg.
It doesn't use everyone's favorite brand of oil or gas.
With my commute, going 67 miles without slowing down, I think I might be able to hit 50 mpg if I went 60. At least until a semi rear ends me. Honestly though, that would be dangerous.
 

· The Nuclear Option
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I'm watching this conversation so it doesn't get out of hand. ;)

If you want to run 87, here is what you can do. If the car isn't stock, return it to stock condition. Clean the induction system and fuel system well. Change the spark plugs Stop monitoring your PIDS and forget everything you know about mechanics.

Then you can drive worry free on 87 just like GM recommends in the owner's manual.

Otherwise pay a little more and use premium gasoline. You'll thank yourself.
 

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Discussion Starter · #7 ·
I wouldn't have thought this would be controversial lol. The whole point of the car, the reason it exists, is to save people money.

I could drive 72 both ways, and that would save me money, but I'd have to leave 8-10 minutes earlier, and well, I always intend to, but it never seems to happen.


Edit

Only things that are not stock are the fuel fill vent valve, which allows me to get gas once every 4 days, and I cut the bottom off the extension off the bottom of the air box, so I could hear the turbo/bov. Pic in my album.
 

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Finally got ahold of my DIL's '14 to try to find/fix that P0299. (I think I got it, too. :))
Anyway, she's put 7700 miles on that car since December, and according to the DIC has been averaging 27mpg @ 55mph avg speed. All she runs is 87 octane. Thats with snows on it and her Indy-car inspired driving habits, too. :ROFLMAO:
So Im happy with that, as the mpg can only go up from there.....
 

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IMO Trifecta is the best option. Even though when I contacted them they had very little interest in making a MPG based tune. But the times are a changing.
How are they the best option if they don't want to provide an Economy tune? lol... @[email protected] from BNR gladly made one for me, keeps the car out of boost and increases mileage a ton.
 

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My old 12 I ran nothing but 87 octane through it. Traded it in at 190,000 miles. Semi synthetic oil when the OLM said to change, air filter every 50,000 miles or so, first set of plugs af 90k and the second set at 150k. Drove 125 miles round trip for work every day with a heavy foot and it probably got 28 MPG. 80k miles from the first set of Michelins and another 80k on the second set. 125k miles on the first set of front brakes and still had the original rear brakes when traded in.
 

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Toss in a set of the NGK Ruthenium HX plugs. They are a longer life alternative to these:

The OEM NGK IFR/AC Delco 41-121 plugs are simply a long-life plug; they run like boggy crap. The 1.4T has a totally different character to it with just a set of these in it, enabling you to use more of the low-end torque of the little motor, especially in the manuals.
 

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OE plugs are the best but might benefit from a slightly tighter gap.
Why would you use 'ruthenium' when the GM spec calls for Iridium ?
 

· The Nuclear Option
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OE plugs are the best but might benefit from a slightly tighter gap.
Why would you use 'ruthenium' when the GM spec calls for Iridium ?
Ruthenium plugs weren't in existence, at least readily, in the 2011 - 2016 time frame. Therefore GM couldn't recommend them.

That being said when my car was stock I tried Ruthenium spark plug and couldn't tell any kind of a difference vs. Iridium plugs.
 

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That's an NGK ad. Of course they will say they are better.
 
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