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What fuel Grade do you use

  • 87

    Votes: 78 76.5%
  • 89

    Votes: 11 10.8%
  • 91

    Votes: 6 5.9%
  • 93

    Votes: 7 6.9%
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Discussion Starter · #1 ·
Fuel Grade is a debatable topic for the Cruze. I've been using midgrade (89) whenever I fill up. I've noticed more consistent mileage and slightly better mileage as well.

Upon further investigating the Cruze's 1.4L ECOTEC Engine, I finally found the engine specs (link below), and noticed a compression ratio of 9.5:1. Now knowing that, I'm glad I put in midgrade at least, especially since it is a turbo car.

Cars that require premium fuel usually have a compression ratio over, 10, ours being at 9.5 I think warrants a minimum of midgrade for better operation. But I'm not a Engines Engineer, and I know the Cruze has knock sensors that allow it to use 87 octane, but I'm sticking with midgrade or higher.

http://www.caranddriver.com/var/ezf...lication/aa4d3fb0ba817b1b2471aedffb210f44.pdf
 

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89 is yielding better fuel economy and more power according to my butt dyno then 87 did. There was a lot more hesitation with 87 and made the sluggish transmission feel even worse due to the hesitation
 

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...wonder if the "higher-is-better" attitude continues when gasoline prices climb toward $4-$5 later this year?!?!

...I doubt it...except maybe during certain "race" weekend outings (ha,ha).
 

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...I'll bet it'll end up being a "...buy it (89-91 octane) when you need it..." situation in the long run for most people...such as driving through mountainous areas, pulling heavy loads, etc.
 

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I have been using 87 and getting satisfactory results. However, I am definitely willing to spend the extra buck and quarter per tank if we can conclude 89 makes a tangible improvement. With the weather improving rapidly (hopefully) we may have to wait until it stabilizes some before we can compare tank to tank to tank.
Has anybody been keeping actual data on this?
 

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It's 10cents more, on a 15 gallon tank is a mere $1.50 per tank (which is less then 1 gallon of 87). the price difference is negligible really - I use about 1.5 tanks per week, so I might spend about $1.75-$2.00 extra each week (to compare, I spent more on soda in 1 day).
 

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Discussion Starter · #13 ·
Assumptions:
- Midgrade fill up costs $1.56 more than regular (empty fill up)
- Midgrade offers a 2.5% increase in fuel economy (probably high but bare with me)
- Average economy on regular = 30 MPG (468 Miles per tank)
- Regular Gas costs $3.50
- Average American Drives 12,000 miles per year
- $1,400/ year in fuel costs
- You keep the car for 8 years

Number Crunching:
- New Economy = 30.75 MPG
- Miles Per Tank (480), extra 12 miles for every fill up
- You would save $1.21 a tank
- $1,404.88/ year in fuel costs
- You would spend $29.27 more in fuel over the life of the vehicle


Conclusions:
- You would end up spending $0.35 more per tank. But the part I'm more interested in is if it isn't as hard on the engine as regular fuel is. As I mentioned in the first post, it does have a relatively high compression ratio to run regular fuel would could hurt the engine over thousands of miles.

- So the extra $30 I may spend over the next 8 years is negligible if means I can get an extra year or more out of the engine

I made some pretty big assumptions here so don't flame me for the numbers I got.
 

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It's 10cents more, on a 15 gallon tank is a mere $1.50 per tank (which is less then 1 gallon of 87). the price difference is negligible really - I use about 1.5 tanks per week, so I might spend about $1.75-$2.00 extra each week (to compare, I spent more on soda in 1 day).
• 10¢/gallon
• $1.50/tank
• 1½-tanks/week
• 52 weeks/year

...and that breaks down to about additional $117 per year...at current price/gallon.
 

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• 10¢/gallon
• $1.50/tank
• 1½-tanks/week
• 52 weeks/year

...and that breaks down to about additional $117 per year...at current price/gallon.
There is always a price difference of $.10 so that's not just "current" prices. I'm hoping that a small bump in fuel efficiency will offset the price of the extra $1.50 per fillup
 

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Discussion Starter · #17 · (Edited)
There is always a price difference of $.10 so that's not just "current" prices. I'm hoping that a small bump in fuel efficiency will offset the price of the extra $1.50 per fillup
If you look at my post, the numbers I have include the MPG gain of 2.5%, but it's also at an average of 30MPG and on a 12,000 mile per year basis. So the assumptions I made are drastic, but give a basis of comparison
 

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If you look at my post, the numbers I have include the MPG gain of 2.5%, but it's also at an average of 30MPG and on a 12,000 mile per year basis. So the assumptions I made are drastic, but give a basis of comparison
exactly, a possible $4 more per YEAR on gas, that's pretty much even to me. Even if the 2.5% you figured was slightly lower
 

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If the car is tuned for 87 then you should run 87, period. Higher octane fuel is only going to waste your money if the car is tuned for 87. Higher octane fuels are used to prevent detonation, often referred to as knock. Detonation is when cylinder temperature or pressure is high enough to cause combustion before the spark plug fires. The higher the octane rating the the more resistant the fuel is to detonation. The car's ECU uses a knock sensor to sense detonation, when it sees knock it will retard ignition timing to lower cylinder temps also causing a drop in hp.

Long story short, if the motor is tuned for 87 from the factory it shouldn't be detonating on 87 octane fuel and using higher octane is only going to waste money...
 
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