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Discussion Starter · #1 · (Edited)
So I was thinking,
Premium fuel is pretty high in price.
I usually fuel regular.
And as some have noticed, the Cruze doesn't do well with regular when the temps exceed 100F.

I was thinking in my 13Gal fuel tank, to add 2 gallon of E85 fuel for every 11 gal of Regular fuel.
It should be exactly the same price as a tank of regular, but it'll result in E14 (higher knock resistance than regular, pretty similar to Premium fuel).

The price of a full 13GAL tank here locally at $2.69/gal is exactly $35.
This would be the same as a tank of Regular + E85, as E85 is sold here at the same price as regular (in your area too?).
If I would fill up with premium, at $3.09/gal, I would pay $40 for a tank.

$5 extra for a tank might seem silly, especially since Shell premium fuel usually has 5% better MPG than Shell regular (which brings the total price closer to $3 surplus per tank).

And I'm only expecting that 2 gal of E85 is enough to make the fuel similar to Hi-Octane fuel in terms of knock resistance, which is more of a guess than an actual measurment.
Open for discussion on more technical data on E85 octane rating!

So, if I would do 500 miles on a tank of regular fuel (13GAL),
I would do 525 miles on a tank of Premium (Hi Oct) fuel under the same conditions.

On the other hand, E85 is about 30% less efficient than regular fuel (according to some sources, more proof needed) , so in order to go just as far as 13 gallons of regular fuel, I would do:
11 gallons of regular (500/13*11) + 2 gallons of E85 (500/13*2*0.6), and that gives me 470 miles.

Now we can compare the range of all tanks (regular, Regular + E85, and premium), with the price paid:

Reg: 14.28 miles per dollar.
Prem: 13.12 miles per dollar.
Reg+E85: 13.42 miles per dollar.

When we look at the above numbers, and use Regular as our reference (base), and convert the miles/dollars to percentage, we get:
Reg: 100%
Prem: 92%
Reg+E85: 94%

Our current numbers indicate going Premium is the least economical, and going regular is the most.
And adding 2 gal of E85 in an 11GAL regular tank, will result in a 6% loss, however, there will be less heat soak/knock losses.

Using regular + E85 over Premium would make sense, if Premium gasoline prices are 10-15% (or higher) priced than regular fuel.
Otherwise (premium fuel prices are <10% surplus over regular), use premium gasoline.


Most people wouldn't go through the trouble of mixing E85 with regular, if your local pump doesn't serve E85; but if you have both fuels at the same pump near your home, why not?

Open for discussion!
 

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From the manual courtesy of Nick!

"However, E85 (85% ethanol) and
other fuels containing more than
15% ethanol must not be used in
vehicles that were not designed
for those fuels."


Why not try a gallon of Sunoco 103 Racing fuel or "Sunoco 100"

Sunoco SS 100 is an unleaded high octane gasoline that is street-legal in California. Its 100 octane rating will allow increased boost levels in supercharged or turbocharged applications compared to premium pump gas. Sunoco SS 100 can be used in high performance vehicles both old and new.
 

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Discussion Starter · #3 ·
Another thing they've noted, was that the E85 fuel, has more water in the fuel, the nature of Ethanol, to attract water, which causes the engine to cool down more, and could result in better fuel efficiency.
 

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Discussion Starter · #4 ·
From the manual courtesy of Nick!
"However, E85 (85% ethanol) and
other fuels containing more than
15% ethanol must not be used in
vehicles that were not designed
for those fuels."


Why not try a gallon of Sunoco Racing fuel or "Sunoco 100"

Sunoco SS 100 is an unleaded high octane gasoline that is street-legal in California. Its 100 octane rating will allow increased boost levels in supercharged or turbocharged applications compared to premium pump gas. Sunoco SS 100 can be used in high performance vehicles both old and new.
Mainly because of price, and we're not racing the engine, just trying to prevent knock or delayed ignition due to hot outside temps.
Racing fuel with 100oct would be nice to add to regular fuel, if they were cheaper than Hi-Oct fuels (usually 92/93)
 

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My personal recommendation would be to fuel the car with 91+ octane.

As you've noticed the Cruze computers are sensitive to knock and will retard engine timing to protect itself if it senses pre-detonation. Knock is caused by the fuel exploding too early in the cylinder due to high temperatures, and high pressures. Since the Cruze is turbo charged, it's a check mark for high pressure. The intake temperatures vary wildly depending on conditions. But basically you're going to reach high temps at least a few times each tank of fuel. The exception is in winter when the temps are always cold.

I've toyed around with various grades of fuel and have settled on 93. I get better fuel economy with premium, which is almost enough to completely offset the price increase. Also, when I run 87 my car is very quick to pull timing and as a result it feels very under powered. Just feed it premium. It's not like it chugs gas. A car is generally your second biggest purchase, no sense in fooling around with mixing fuels it's not recommended to run just to save a few dollars. If you really want to save money on fuel, buy a 50cc scooter on craigslist, they get 110+ mpg and I wouldn't feel the least bit bad for filling it with 87 octane. Or bicycles I hear are an option for some people. Much cheaper.
 

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It has been noted here in this forum cars with the 1.4 perform better with mid grade or better fuel vs your 85 or 87. I personally use 89 octane in my LT RS ans my car is not tuned. So the cost savings you are referring to is traded to performance.
 

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That's crazy that E85 is the same price as regular. E85 (I run it full time) is typically $2 or less by me.
 

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Discussion Starter · #8 ·
My personal recommendation would be to fuel the car with 91+ octane.

As you've noticed the Cruze computers are sensitive to knock and will retard engine timing to protect itself if it senses pre-detonation. Knock is caused by the fuel exploding too early in the cylinder due to high temperatures, and high pressures. Since the Cruze is turbo charged, it's a check mark for high pressure. The intake temperatures vary wildly depending on conditions. But basically you're going to reach high temps at least a few times each tank of fuel. The exception is in winter when the temps are always cold.

I've toyed around with various grades of fuel and have settled on 93. I get better fuel economy with premium, which is almost enough to completely offset the price increase. Also, when I run 87 my car is very quick to pull timing and as a result it feels very under powered. Just feed it premium. It's not like it chugs gas. A car is generally your second biggest purchase, no sense in fooling around with mixing fuels it's not recommended to run just to save a few dollars. If you really want to save money on fuel, buy a 50cc scooter on craigslist, they get 110+ mpg and I wouldn't feel the least bit bad for filling it with 87 octane. Or bicycles I hear are an option for some people. Much cheaper.
I've noted that many premium blends, Shell, BP, use nitrogen based boosters, causing more violent combustion, and the engine to vibrate more, while E85 uses a much more slow burning, better suited for low revving cars like the Cruze.

I've always felt like my engine would wear quicker when I use hi octane fuels from BP and Shell, for this purpose.
 

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I've noted that many premium blends, Shell, BP, use nitrogen based boosters, causing more violent combustion, and the engine to vibrate more, while E85 uses a much more slow burning, better suited for low revving cars like the Cruze.

I've always felt like my engine would wear quicker when I use hi octane fuels from BP and Shell, for this purpose.
Well I can't help how you "feel" about it, but the owners manual recommends using Top Tier fuel for engine longevity. By ignoring the engineers that designed the vehicle, and deciding to make your own uninformed decisions might end up shortening the life of the vehicle. The use of E85 will void your warranty because it is listed under the "Prohibited fuel" section of the manual.

fuel1.PNG fuel2.PNG

My final thoughts: Do not run E85 in the Cruze. Do not fuel with cheap off-brand fuel from low volume gas stations. 87 octane is OK to use but will feel under powered due to decrease in timing. 89+ is preferred. And I still personally recommend 91+ for the best fuel economy and greatest knock resistance. You are your own person capable of making decisions so good luck with your choice, whatever it is but I have a feeling you've already made up your mind.
 

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With the correct injectors there is no issue running E85. Also, it *may* void your warranty. I personally use it and have for 30k miles and my dealership hasn't turned me away for anything. I also believe it has been noted to run better in our vehicle's than the recommended fuels. I have almost no ticking like I did on the recommended fuels. (93 from BP and Speedway were considered best near me). I also have more HP compared to those on 93 and a tune. I run E85 and a BNR tune.
 

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Well I can't help how you "feel" about it, but the owners manual recommends using Top Tier fuel for engine longevity. By ignoring the engineers that designed the vehicle, and deciding to make your own uninformed decisions might end up shortening the life of the vehicle. The use of E85 will void your warranty because it is listed under the "Prohibited fuel" section of the manual.

View attachment 243050 View attachment 243058

My final thoughts: Do not run E85 in the Cruze. Do not fuel with cheap off-brand fuel from low volume gas stations. 87 octane is OK to use but will feel under powered due to decrease in timing. 89+ is preferred. And I still personally recommend 91+ for the best fuel economy and greatest knock resistance. You are your own person capable of making decisions so good luck with your choice, whatever it is but I have a feeling you've already made up your mind.
I agree and at the same time disagree with you. What is "off brand fuel". Is their a special off brand refinery located regionally to provide inferior fuel to smaller 'low volume' retailers like Safeway or Kroger. The CRUZE is not meant to run on Flex fuels, especially 85% Ethanol. Top Tier is one of the biggest myths that anyone can believe in. What's in it, why do certain stations like BP charge less for this special blend. Why does the same Gas tanker that services Top Tier stations then drive across the street and service the non top tier stations. Is Top Tier like a fizzy tablet (soft drink novelty of the 70's) dropped in by the Tanker driver at certain stations. Why have Gas companies had their own proprietary versions of Top Tier for the last 100 years or so. Why should a CRUZE Tick or Ping, mine certainly doesn't although it does get sluggish in hot weather which is easily remedied with higher octane fuel. The AAA claims non Top Tier users will see 19 times the amount of Carbon deposits after 4000 miles of non Top Tier use causing terrible problems yet...

Despite the fact that two-thirds of U.S. drivers believe there is a difference in quality of gasoline sold by different gas stations, a AAA survey reveals that Americans value convenience and price over quality when it comes to selecting a gas station.

  • Three-quarters of U.S. drivers choose a gas station based on location (75 percent) or price (73 percent).
  • Nearly one-third (29 percent) of U.S drivers choose a gas station based on a rewards program.
  • Only 12 percent of U.S. drivers select a gas station based on whether the gasoline contains an enhanced detergent package.
  • Nearly half (47 percent) of U.S. drivers do not regularly buy gasoline that contains an enhanced detergent additive.
  • Men (44 percent) are more likely than women (26 percent) to regularly buy a gasoline that contains an enhanced detergent package, as are baby boomers (41 percent) compared to millennials (32 percent).
“Americans are six times more likely to choose a gas station based on the price of gasoline rather than the quality of the fuel,” continued Nielsen. “Since TOP TIER gasoline is widely available and only an average of three cents more per gallon, AAA urges drivers to reconsider their priorities when selecting a gas station.”
 

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Why does the same Gas tanker that services Top Tier stations then drive across the street and service the non top tier stations.
The tanker driver has to set the mix when he delivers, the detergents aren't in the big tank on the trailer.
For example, he might put 150ppm of the Marathon/STP additive package in Speedway's underground tanks and 400ppm of the same detergent in the Marathon station's tanks. (I'm working from memory and might have the numbers wrong, but there's a lot more of the stuff in Marathon gas than there is in Speedway) Then he drives to the Shell station and mixes entirely different additives in the gas he delivers there.

That's why it surprised me when an earlier post in this thread mentioned Speedway as one of the best fuels.

What's interesting is that all grades of Shell are Top Tier certified, but Shell Premium is advertised as having something like twice the additives as Shell Regular and Midgrade.

Around here, 93 octane costs 60 cents per gallon more than 87 octane, except at Shell stations where it costs 70-90 cents more than 87. Some of my cars that don't get driven much get Shell 93 under the assumption that it has way more detergent than is useful in normal driving. The low fuel light came on in my S420 last month and I planned on filling it the next time I drove it, but I haven't driven it lately so it still has 2 gallons of Shell I bought back in March. I should have filled it last week, now it's probably too late to get summer gas for it.
 

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Discussion Starter · #13 ·
I don't think adding 2 gal of E85 fuel will cause any major damage to the engine, especially if you ride it off pretty frequently (fuel up at least once a week).
Regular gasoline already has UP TO 10% of corn juice in it.
And from my experience here in SoFlo, Marathon is closer to the 10%, while Shell is closer to 2%.

As long as the concentration is not too high, it shouldn't do too much damage.
What causes most damage, is water getting in the fuel tanks, 'drowning' the engine with non-combustible fluids, that work best on a hot engine.
 

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I run Premium in my Cruze since I bought it as a 2014 leftover in Feb of 2015....I now have 16,000 miles on it and used up all of my 3 year oil change agreement. I plan to go with good synthetic oil once I start changing my own and I will continue to use 92/93 octane fuels as long as I own it.
 

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I decided to fill up with 93 Shell V Power to see what the difference is, and since I had 65 cents off with Fuel Rewards Network figured I'll try it. Only about 30 miles in and maybe just in my head, but it seems like accelerating is a little faster/smoother. Prem is around ~80 cents more compared to 87. I have only filled up 3 times with 87 and my average is ~34MPG when calc fuel vs miles. The car reading is a little off since it told me 37.1. Be interesting to see if I see any improvements with 93 on MPG, I might switch back to 87 since I m thinking I will not get more milage to make up the difference in cost and will just see a boost in my head. Would just filling up 1 time with 93 would I see MPG improvements or would I need to use 93 for a few tanks to really see something?
 

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I decided to fill up with 93 Shell V Power to see what the difference is, and since I had 65 cents off with Fuel Rewards Network figured I'll try it. Only about 30 miles in and maybe just in my head, but it seems like accelerating is a little faster/smoother. Prem is around ~80 cents more compared to 87. I have only filled up 3 times with 87 and my average is ~34MPG when calc fuel vs miles. The car reading is a little off since it told me 37.1. Be interesting to see if I see any improvements with 93 on MPG, I might switch back to 87 since I m thinking I will not get more milage to make up the difference in cost and will just see a boost in my head. Would just filling up 1 time with 93 would I see MPG improvements or would I need to use 93 for a few tanks to really see something?

Brace yourself, this could get boring.

It may take a few tanks to get the full benefits of a highly knock resistant fuel like 93. The car has knock sensors and will "pull" or retard the timing on the engine if it senses knock (aka pinging or predetonation). Knock happens when you put the air/fuel mix in a condition where it spontaneously combusts before the spark plug gets a chance to ignite it at the optimal time. When the air/fuel detonates too early, it can harm the engine. The cruze has timing tables for fuel as low as 87 octane so you can safely run cheap gas but there are side effects. The 1.4L engine in the Cruze is turbo charged so the air pressure going into the cylinder is higher than naturally aspirated cars. When you increase pressure of a gas, the temperature increases. Some of that extra heat is removed by the intercooler. But since the intercooler is sandwiched in between the coolant radiator and the A/C radiator, it will often heat soak in the summer, in traffic, or with A/C use. That's when the air intake temps skyrocket and cause knock, so the computer retards timing to protect itself which results in decreased power. Not a huge deal, but since the Cruze is heavy, and doesn't have a lot of power to begin with, now it has to use more fuel hence the decreased economy. Depending on how you drive, you may not notice it. But if you have a lead foot, you'll lose a pretty significant amount of MPGs running 87.

You can kind of get away with running 89 or 87 in the winter because the intake temps stay low. When air is cold, it's dense and more potent. Usually that means you can get more power, but the Cruze is torque limited so it uses the boost levels to control how much torque it makes. Since it can easily achieve the 148 ft-lbs in the winter with that delicious dense cold air, it doesn't need as much boost so the pressure is lower, which means the temps are lower, and since the winter air is already a lot colder, the air fuel/mix is a lot less likely to pre-detonate so the computer doesn't need to retard the timing. You'll still get less fuel economy in the winter no matter which grade you run because they have to blend in extra chemicals to keep the fuel from freezing, and it also takes the car a lot longer to reach operating temperature so it runs rich more often in winter.

Hope this helps.
 

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I don't think adding 2 gal of E85 fuel will cause any major damage to the engine, especially if you ride it off pretty frequently (fuel up at least once a week).
Regular gasoline already has UP TO 10% of corn juice in it.
And from my experience here in SoFlo, Marathon is closer to the 10%, while Shell is closer to 2%.

As long as the concentration is not too high, it shouldn't do too much damage.
What causes most damage, is water getting in the fuel tanks, 'drowning' the engine with non-combustible fluids, that work best on a hot engine.
I used to fuel up at a northern IL Marathon station as it had the best price for 87 octane (old 360 BB ford) and I used about 2 tanks a week. I noticed that I was getting lousy mileage as compared to when I fueled up in WI. At the time, IL dropped the fuel tax so gas in IL was then cheaper. Needless to say I no longer purchase from Marathon.


Brace yourself, this could get boring.

It may take a few tanks to get the full benefits of a highly knock resistant fuel like 93. The car has knock sensors and will "pull" or retard the timing on the engine if it senses knock (aka pinging or predetonation). Knock happens when you put the air/fuel mix in a condition where it spontaneously combusts before the spark plug gets a chance to ignite it at the optimal time. When the air/fuel detonates too early, it can harm the engine. The cruze has timing tables for fuel as low as 87 octane so you can safely run cheap gas but there are side effects. The 1.4L engine in the Cruze is turbo charged so the air pressure going into the cylinder is higher than naturally aspirated cars. When you increase pressure of a gas, the temperature increases. Some of that extra heat is removed by the intercooler. But since the intercooler is sandwiched in between the coolant radiator and the A/C radiator, it will often heat soak in the summer, in traffic, or with A/C use. That's when the air intake temps skyrocket and cause knock, so the computer retards timing to protect itself which results in decreased power. Not a huge deal, but since the Cruze is heavy, and doesn't have a lot of power to begin with, now it has to use more fuel hence the decreased economy. Depending on how you drive, you may not notice it. But if you have a lead foot, you'll lose a pretty significant amount of MPGs running 87.

You can kind of get away with running 89 or 87 in the winter because the intake temps stay low. When air is cold, it's dense and more potent. Usually that means you can get more power, but the Cruze is torque limited so it uses the boost levels to control how much torque it makes. Since it can easily achieve the 148 ft-lbs in the winter with that delicious dense cold air, it doesn't need as much boost so the pressure is lower, which means the temps are lower, and since the winter air is already a lot colder, the air fuel/mix is a lot less likely to pre-detonate so the computer doesn't need to retard the timing. You'll still get less fuel economy in the winter no matter which grade you run because they have to blend in extra chemicals to keep the fuel from freezing, and it also takes the car a lot longer to reach operating temperature so it runs rich more often in winter.

Hope this helps.

That was a mouthful! Pretty interesting though.
 

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I had about 5 gallons of Marathon 87 octane E10 in my 2.2L Ion this afternoon when I dumped 2 gallons of E85 in it and drove it to town. The car didn't care one bit. I even ran it up to 4000rpm WOT, no discernable difference. Got to town and put another 6.4 gallons of Marathon regular in it.

So I suspect, but do not know, that the PCM in a Cruze can deal with 4 gallons of E85 in a full tank. I do know that a 2007 Saturn Ion's Ecotec can deal with it.

The next question is whether it would do long term harm, as the Cruze 1.4 is not certified for over E15 in USA.
 

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Discussion Starter · #19 · (Edited)
I can only compare it to my current Fiesta ST.
However, the Cruze should be under the same regulations.
They're made to be compatible with E15. On my Fiesta ST, there's a note "No fueling E20-85".
Strange. I probably could fuel diesel, or E100 and get away with it, 'legally' that is, because the sticker didn't mention not fueling anything above E85 nor diesel.
Anyway,
My experience with E fuels indicates that my ST is running better on a blend of 50% regular 87 octane, and 50% E15; resulting in ~E10-E12, with a 88 octane rating.
Anything higher (pure E15, E30,..) runs less efficient (lower MPG) and less power.

The hotter your engine runs, and the more knock it has, the higher you can tune your Ethanol levels.
If your engine runs very cool, on the stock turbo, there's no reason to believe it actually has more power on E15 or above, than below.
In fact, more than likely, the higher you go on ethanol levels, the lower your performance.
Unless you compensate by higher exterior temperatures, higher compression ratios, higher boost, or higher back pressure.

I think the only cars that benefit from E15 would be the 1st gen 2012+ models that are made to support E15 fuels, as they run considerably hotter than the Gen 2 models.
The 2011 Cruze (and especially the Eco models) don't have the proper fueling system to deal with higher ethanol fuels, and you probably could get away with E12 for a while.
But 93 octane is still a bit better.
I wouldn't do E15 in them, as they are made for E10 fuels and no more.

Running too much E85 in your fuel, and your car will run lean.
Some people on the Fiesta forum (especially those tuning their cars) have ran into piston problems due to lean burn, due to running too high ethanol levels (E50 and up).

If you had a dyno, you could do tests with what works best on your car.
But for my Fiesta, the butt dyno tells me the car accelerates best at 50% 87 octane, with 50% E15 fuel in a tank.
If your Cruze runs hotter, that ratio might be different.
You'd have to experiment.
And if you notice where the power starts to decrease (eg: E30 or E40), half that number, and that's roughly where your sweet spot is.
Eg: E40 starts accelerating slow, E20 is your sweet spot. Then try testing out E15 with E15+1 gal of E85.
I seriously wouldn't go over E20.
 
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