UNL88 gas

Discussion in 'Engine & Drivetrain' started by RGB1978, Sep 8, 2019.

  1. RGB1978

    RGB1978 TYF Newbie

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    Can anyone tell me if it’s ok to run UNL88 has in a 2001 Yukon with a 5.3L engine?


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  2. Scottydoggs

    Scottydoggs Full Access Member

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    google says its ok for 01 and newer cars. give it shot. only draw back might be lower mpg, but if its cheaper the offset will balance its self out.
     
  3. iamdub

    iamdub Hold on... Lemme overthink this for a bit...

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    It's fine as long as you don't drive it under heavy load (hard throttle, high temps, towing, etc.). LS engines, especially the Gen4 and newer, tend to benefit from 89 or higher even though the manual specifies that minimum 87 octane is ok. I can hear and feel a difference in mine with the different grades and usually run 93 because I like acceleration and the temps are often in the 80s-90s most of the year.
     
  4. RGB1978

    RGB1978 TYF Newbie

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    I’m an engineer, so I love data. I’ve always heard there’s no appreciable benefit in running premium versus regular gas. A few years ago when I ran across premium at a discounted price, I decided to try an experiment. I track my gas mileage so I know what MPG I get for regular. I decided to run 10 tankfuls of premium gas and compare my gas mileage. Not only did I notice an improvement in acceleration but my MPG improved 9%. So whenever I can buy premium at a price not higher than 10% above the cost of regular gas I buy it.

    Now back to UNL88.....can anyone tell me what engine change took place between 2000 and 2001 that determined the cutoff for who can and can’t use UNL88?


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  5. iamdub

    iamdub Hold on... Lemme overthink this for a bit...

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    Saying there's no appreciable benefit in premium versus regular is far too broad of a statement. Most cars, by a huge margin, are designed to operate on 87-89. Of that majority, most of the newer ones benefit from higher grades because they have higher compression (static and dynamic) and advanced timing to squeeze out more power from smaller displacement. But, they have alternate programming to operate just fine on the lower grades. Some of the higher-end luxury and/or sport cars actually list the power differences between the grades in the owner's manual. Case in point: A friend's new Mustang with the Ecoboost 4-cylinder specs a 35HP and 20TQ loss if 87 is used instead of 93. But it doesn't say you can't run 87.

    I never would've guessed your Gen3 would've benefited so much from switching to high octane. Good on you for tracking your mileage so accurately!

    Specifically for the GMT800 trucks, I don't know of any changes between '00 and '01 that would effect minimum octane requirement on the iron block 5.3. Those engines remained largely the same with the biggest change being the Drive By Wire throttle body for the '03 models.
     

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