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Octane Rating and Fuel Economy

4K views 4 replies 4 participants last post by  obermd 
#1 · (Edited)
I have a few stupid questions for you guys! Lurked the forum a bit, but still have some stupid questions.

Bought a 2018 Cruze, and found in the manual that apparently I should only use 87 and higher, with no more than 15% ethanol. I have no idea what the dealer filled me up with, but I put in 89 for the **** of it. Gas mileage is minimally better, but the car feels much more peppy and smooth. It's not as sluggish or jerky as it was previously during acceleration.

Here's the question everyone seems to debate, is there any reason to use 91, or look for lower ethanol levels? Would a higher rating actually increase efficiency or performence more so?

Second question, I currently live in a high altitude city. Once I move to sea level in the next few months, would it be beneficial to use a different octane level? Apparently air pressure is a factor in all this.

Sorry for the stupid questions, never owned a decent vehicle or something with a turbo, so all the debates on the subject can be confusing for an idiot like myself ? With my previous rust buckets I just tossed in good ole 85, but that's apparently a bad idea with this vehicle.
 
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#2 ·
Owners manuals have always recommended 87. Way back when leaded gasoline was around.

the consensus says run 91. Specially if you move to sea level altitude.

Some people notice a difference. Some don't. But no one has said their altitude and amospheric pressure and humidty. To see if there might be some sort of correlation in octane to performance.

Los Angeles to Miami for instance. Dry air vs. the wettest air in the country. OR. Los Angeles to Denver. Difference of 2.5 pounds atmospheric pressure between the 2 cities.

Atmospheric Pressure at sea level is 14.7 psi. It drops .5 for every 1000 feet. Then you got dry air on the western hemisphere. Humidity on the eastern hemisphere.
 
#4 · (Edited)
Thanks so much guys! You rock for the insight and fast responses! I'll try out 91 and see what happens after I get reliable numbers from 89.

Figured if I'm paying on a vehicle for a decade, id love to take care of it the best I can! In the past I was just happy if I didn't have to have the tranny rebuilt or the heads replaced and couldn't afford to think of fuel grades lol.

It's hard to get a solid answer due to the debates with fuel grades. Currently living in Salt Lake City, which is very dry and high altitude. Moving down to Texas within about two hours from the coast.

Just curious on what the air pressure change and nasty high level of humidity may do to performance and if another grade may be recommended.

It may be cool to have a poll around and see what impact air pressure and humidity has regarding users of the same octane level with performance and efficiency.
 
#5 ·
Test two or three tanks (run to nearly empty before filling with a different octane) and see for yourself. What you're looking for is the right balance for your driving style and environment.
 
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