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2021 Chevy Trailblazer RS AWD
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The first time I filled the enormous (13.2 gallon) tank, I packed in 10.49 gallons. Over 300 miles driven (and some idling) that equates to 28.8 mpg. I do not drive like I'm on an economy run, so that mileage is fine. I have no clue of the stealership packed the tank full, the same as I, so it could be a little better.
 

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2nd tank 31.9 MPG, mostly highway. 13.2 gallon tank. Put in 11.9. Low fuel alert NOT on, last light square lit.
 

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Question about gas for this car: the manual says recommended minimum of 87 octane. I know it has a turbo in it and in my experience with turbos they usually require higher octane. So, is 87 sufficient like the manual says, or should I use mid-grade or higher?
 

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I am following the manual’s recommendations.
 

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2021Trailblazer RS AWD Scarlet Red Metallic
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Question about gas for this car: the manual says recommended minimum of 87 octane. I know it has a turbo in it and in my experience with turbos they usually require higher octane. So, is 87 sufficient like the manual says, or should I use mid-grade or higher?
Good question. I've been running 91 octane since my first fill up and my average mpg has been 29 which is close to the rated combined mpg. The little 3cyl seems to like the 91 better, probably because it stays on the high octane map which will alllow more spark advance and timing which equals more power. From my experience with other small turbo engines especially the 2012 Cruze I had a few years back they really do benefit from higher octane. Do you need to run 91, absolutely not. The engine is certified to run on 87 and will run just fine plus you may not gain any mpg with 91 so it will cost more money at each fill up. I guess the answer is if you want a little more power and smoother running engine go with 91, but if you care more about saving money go with 87.

Steve
 

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Good question. I've been running 91 octane since my first fill up and my average mpg has been 29 which is close to the rated combined mpg. The little 3cyl seems to like the 91 better, probably because it stays on the high octane map which will alllow more spark advance and timing which equals more power. From my experience with other small turbo engines especially the 2012 Cruze I had a few years back they really do benefit from higher octane.

Hi Steve, I'm interested to better understand what metrics of engine performance improved with higher octane and how they were measured. I've heard people say everything from better mileage, better horse power &/or torque, better (less) wear & tear, etc. but rarely have I seen anything that demonstrates these claims. In your case, is this something that you've measured quantitatively?
 

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Hi Steve, I'm interested to better understand what metrics of engine performance improved with higher octane and how they were measured. I've heard people say everything from better mileage, better horse power &/or torque, better (less) wear & tear, etc. but rarely have I seen anything that demonstrates these claims. In your case, is this something that you've measured quantitatively?
I've personally recorded a slight increase (2mpg) in gas mileage with 91 vs 87 octane and I've noticed the engine responds better to 91 vs 87. The idle is smoother and there is more power available in the entire rpm range due to the PCM using full timing/spark advance. The gas mileage increase is easy to calculate if you use the same gas pump and save your receipts and do the math. The gas mileage calculated by the vehicle isn't exact and can be off by 5% or more. The increase in hp/tq is not as easy to verify since you would need a dyno and run the vehicle with 2 different octanes to see the difference. Not every vehicle responds the same way to higher octane. Some can actually get lower gas mileage and no increase in hp/tq. In general engines with 10.0:1 or higher can typically benefit from higher octane. Small turbo engines tend to run much hotter than non turbo engines. The 1.2T and 1.3T engines in the Trailblazer are 10.0:1 CR. Using 91 octane keeps the engine on the high end of the timing/fuel maps which gives the maximum available hp/tq. The reason why modern engines can run 87 even in high CR engines is due to VVT, SIDI etc. My 2018 ZR2 has a 3.6L with 11.5:1 CR and also runs better with 91. With all that said these little turbo engines will run just fine on 87 since that's how GM tuned and certified them to run, but that doesn't mean there's no gain with higher octane.

Steve
 
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