Recommended Octane grade

VinceS · December 13, 2019

What is the recommended octane fuel grade for these newer 2014-18 trucks??

Jacoby · December 13, 2019

87 unless u got a 6.2 then it’s 93

Snowcamo · December 13, 2019

I run 89 in everything I own, but if I had a 6.2 it'd be 91 or 93 octane.

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Donstar · December 13, 2019

As already suggested, 87 is recommended for the 4.3 and 5,3. I ran 89 up until a few months ago when increasing gas prices were overly impacting my wallet.

I always thought that 89 was more of a placebo effect for me which the past few months have proven. I felt good giving my truck that little extra "boost" but for now the $5 - 10 saving per tank helps ease the impact of ridiculous fuel prices. Run the higher octanes for any reason you choose but you will not harm your truck or notice any reduced function by running 87.

Snowcamo · December 13, 2019

As already suggested, 87 is recommended for the 4.3 and 5,3. I ran 89 up until a few months ago when increasing gas prices were overly impacting my wallet.
I always thought that 89 was more of a placebo effect for me which the past few months have proven. I felt good giving my truck that little extra "boost" but for now the $5 - 10 saving per tank helps ease the impact of ridiculous fuel prices. Run the higher octanes for any reason you choose but you will not harm your truck or notice any reduced function by running 87.

Agreed no harm no foul. I just feel like 89 burns cleaner and the engines run smoother. Only reason I'd worry about running high octane is if the timing was fixed with no adjustment like on the old motors.

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Grumpy Bear · December 13, 2019

87 is recommended and after a few years experimenting all the way to 94 in one unit increments, it is 87 that I've settled on. This wasn't a tank here and a tank there experiment. I have 106,000 miles on this truck and do things like this over thousands of miles and over seasons. Regardless of octane, it starts the same, gets the same mileage, idles the same and feels the same in day to day driving. I don't drive a great deal in the winter so during these months I run E-0 but during the summer E-10. Living in Illinois E-0 sometimes means running 91 as it is what is commonly available and even that is rare. When I travel where I can find 87 E-0 in the winter, it's what I use.

I've never had this truck on the dyno so could not tell you if it makes more power/torque at WOT at any rpm.

I can tell you that it will run a few degrees less KR past 91 octane but it never completely disappears and even when the KR is relatively high it is never is audible. Data logging 87 and 89 shows nothing statistically relevant in KR.

I've never run UNL-88 or greater alcohols as where I live I've never seen a price spread that make it work for me. Ergo I haven't any experience with the Ecotec3 and octane above 94 to relate.

roadkill5.3 · December 14, 2019

93. A look at the compression ratios with the 5.3 will tell you the same thing.
sure, it’s got antiknock sensors which retard the timing when predetonation Or “pinging” is sensed, but a motor with 11:1 should be running high octane pump gas.

CamGTP · December 14, 2019

11.1 isn't that high.

Look at many other engines running 12.1 and higher on pump 87. A good reason is direct injection, the cool effect the fuel spray has is key.

Grumpy Bear · December 16, 2019

This has been asked and answered how many times?

:banghead:

Knock is about cylinder pressure not mechanical compression ratio. There is allot more to cylinder pressure than mechanical compression ratio.

:idiot:

glcbn · December 17, 2019

I've run 93 in my 5.3 since day one! Not necessary, but I do just because!

LRod · December 17, 2019

Same as posted above. Got a new truck 2 months ago with the 5.3, 93 octane since day 1. I just feel more comfortable with 93 regardless what anyone says. Matter of fact, truck was empty at the dealer and I rode with the salesperson when they went to fill the tank. I asked them fill with 93 and they did.

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durandetto · December 17, 2019

I run 93 or e85, mainly because that's what my tune is for. I prefer e85 for the power gains, but with my heavy foot I barely get 9 mpg in my short trip city driving. With 93 same driving conditions I get 12-13 mpg. Keep in mind I drive hard.

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TRKLGND · December 17, 2019

On 12/14/2019 at 3:31 PM, CamGTP said:

11.1 isn't that high.

Look at many other engines running 12.1 and higher on pump 87. A good reason is direct injection, the cool effect the fuel spray has is key.

The L86 is 11.5:1 and has DI and GM recommends premium. Look at your data logs when running 87 vs 93 while towing or running the motor hard. The amount of timing being pulled with 87 is crazy. Hell, there are even differences between brands of 93.

CamGTP · December 17, 2019

The 11.1 comment was for the 5.3. I know GM says use premium for the most horsepower on a 6.2 engines. 87 octane could be ran but is not recommend on the 6.2. The 5.3 is just fine for joe blow to run 87 octane.

I've data logged many trucks with my HP Tuners, I know what the fuels will do. I run 89 octane in my 5.3 because I tuned it for that and or I run E85 in the warmer months.

Jacoby · December 18, 2019

4 hours ago, paracutin said:

The L86 is 11.5:1 and has DI and GM recommends premium. Look at your data logs when running 87 vs 93 while towing or running the motor hard. The amount of timing being pulled with 87 is crazy. Hell, there are even differences between brands of 93.

You should go back and look at the data logs of this thread. Everyone said 93 octane with a 6.2 and 87 with a 5.3.