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When is Regular gas Not Regular Gas

CKNSLS

By CKNSLS
in Ask A GM Technician

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CKNSLS Enthusiast

CKNSLS

Posted
Posted

Hi all!

 

I am currently living in Southern California where I bought my Silverado new (5.3. it's a 2011). In the owners manual it says to use 87 octane regular gas.

 

I am moving in a few days to Utah where regular gas is actually 85 Octane. The mid-grad is 87 octane (which obviously costs more-about 10 cents a gallon).

 

I realize I probably have some smog stuff on my motor not found on other trucks shipped to other states. I know California smog rules are tougher than Federal standards.

 

The question is can I use the 85 octane even though my owners manual says a minimum of 87 octane?

 

If anybody knows I would appreciate some feedback.

Thanks!

SouthCo Senior Enthusiast

SouthCo

Posted
Posted

No... You have to use the minimum required in the manual... ie 87. The truck doesn't know your in Utah and that the regular there is 85. They don't build different motors or tune for each state. They state the minimum octane and you have to be smart enough not to go lower.

CKNSLS Enthusiast

CKNSLS

Posted
  • Author
Posted

OK-no problem there. I am wondering though why 85 is refined as regular in Utah. It's the same octane level no mater what brand you fill up on. So I have never driven a car (in California) that stated lower than 87.

 

So if the motor is no different it must be the smog equipment. Because many cars are filing up with regular at gas stations in Utah. I do not know if I believe it's all owner ignorance.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Usually lower octane is sold in high elevations.

Chris Senior Enthusiast

Chris

Posted
Posted

I went thru this. I have my tuck tuned. My uncle and I went on a business trip to salt lake then to north east Utah. I didn't realize it was 85 because I wasn't filling it up my uncle was with his company card. But I emailed Justin at blackbear. He said the 85 will do no harm at all. You have nothing to worry about. You will get poor mileage if u get high up there and feel the lack in power. If you are taking I-15 and I'm not sure how far your going into Utah but around beaver you will start to climb to about 7500 ft. You will fill it. But your so far above sea level the air pressure is less. Lower compression. My truck ran fine.

 

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BlackZ71Silverado Senior Enthusiast

BlackZ71Silverado

Posted
Posted

If your truck calls for minimum of 87 octane, that's what you need to run. If not you will notice less performance, power and mpg's.

 

 

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markw8 Enthusiast

markw8

Posted
Posted

Areas of the country that are higher elevation get gas blends of lower octane. As you go higher in elevation the engine needs less octane. This has been true for years.

 

Mark

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

I don't think 2 octane points is going to make all that much difference either way.

 

The computer will retard timing if it knocks / pings, which it probably won't do anyway if your driving it where you bought the fuel. Your mileage will actually go up when your at high elevation, because the computer will cut back fuel to match the decrease in o2. You lose power at high elevations whether your driving these newer electronic wonders, or old school carbureted. The carbed one will lose power even more so, because it will be pig rich & inefficient.

BlackZ71Silverado Senior Enthusiast

BlackZ71Silverado

Posted
Posted

I didn't read entire 1st post......the truck will adjust on it's own if you use that fuel. The elevation must be the reson for lower grade.

 

 

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93gmc$$ Enthusiast

93gmc$$

Posted
Posted

No... You have to use the minimum required in the manual... ie 87. The truck doesn't know your in Utah and that the regular there is 85. They don't build different motors or tune for each state. They state the minimum octane and you have to be smart enough not to go lower.

 

 

NOT correct, in Utah (and Idaho where I live), with the higher elevation (Boise 2730', Salt Lake City 4200') the air is thinner, which = less oxygen per volume in the cylinder. The corrrect (stoichiometric) air-fuel mixture will be met with lower octane fuel. Don't waste your money.

hodo78 Enthusiast

hodo78

Posted
Posted

Areas of the country that are higher elevation get gas blends of lower octane. As you go higher in elevation the engine needs less octane. This has been true for years.

 

Mark

 

 

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