5.3 L84 fuel suggestion

Tigerwitha88 · August 18, 2020

Just purchased a 2020 Silverado with the 5.3 L84. Salesman said use 87 octane but looking more into engine specs I was surprised to see it has 11.1 compression. I’ve always been told 11.1 is highest compression you can have in a sbc and run 93 octane pump gas.

Gen. 6 sbc different? How?

newdude · August 18, 2020

These engines are direct fuel injection or DI. DI allows for a more complete combustion and cooler cylinder temperatures that enable a higher compression ratio for greater efficiency and power all on lower octane.

Older multi port/throttle body/carb systems, the fuel and air mixture is heated at the same time, so higher compression on low octane = knocking on port injection. Thus the need for higher octane (resistance to detonation).

The 5.3 is set up to run 87 octane all day long. You can run higher if you choose to, but there is no need with the 5.3.

On the other end of this, the 6.2 wants 93 octane with its 11.5:1 compression ratio. Lower octanes can and will knock, especially under load.

roadkill5.3 · August 18, 2020

with 11:1, no matter the displacement, you should be running high octane. i dont care if its direct injected or if it has a carb.

these motors will sense knock, and ****** your timing to compensate for shitty fuel. same goes with a honda, and this technology has been out there for a very long time.

to get the most out of your 5.3, have less ******, run 93.

i bought my l83 and it had regular in it. the first time i filled up, i ran 93, and what a difference in power and throttle response it had by the second tank.

and to say that the 6.2 NEEDS higher octance more than the 5.3 is not that smart. both are high compression motors, sure the 6.2 has .4 more compression.... and that 6.2 is put in alot of higher end SUV's that soccer moms drive, do you think they run 93 or even 89? i highly doubt it. it just retards the timing, and itll run just fine on 87. but at 87 on either the 5.3 or the 6.2, your not getting the proclaimed HP of the motor nor are you getting the full performance as advertised.

CamGTP · August 19, 2020

Someone that just drives the truck with no care about maximum performance can run 87 octane without a care, it's going to get good fuel mileage on that fuel. Someone running 93 octane isn't just going to walk away in a race with someone running 87 octane. It's not like 93 octane is giving you 25+ horsepower and a couple tenths in the 1/4 mile.

These calibrations are built with knock in mind and it's just fine. I had a few degrees of knock on my truck with 87 at full throttle and less with 89 octane. But I also tune all my own vehicles so I went more in depth with fueling and timing changes to make it better.

Daggs · November 2, 2020

Every 5.3 I have owned (and its quite a few) has had a slight knock on 87. 89 did not do this. There is 1 station that has 93 vs 91 close that I would use. I really didn't notice anything more then the knock, if that helps.

anthony2558 · November 2, 2020

12 hours ago, Daggs said:

Every 5.3 I have owned (and its quite a few) has had a slight knock on 87. 89 did not do this. There is 1 station that has 93 vs 91 close that I would use. I really didn't notice anything more then the knock, if that helps.

Weird. I live in PA, work in NJ. Filling up in Jersey on 91 cause it cost the same as 87 in PA. I've come to the conclusion that the truck runs better on 87. Didn't matter if it was winter gas/summer gas, always used Sunoco.

diyer2 · November 2, 2020

13 hours ago, Daggs said:

Every 5.3 I have owned (and its quite a few) has had a slight knock on 87. 89 did not do this. There is 1 station that has 93 vs 91 close that I would use. I really didn't notice anything more then the knock, if that helps.

Never heard that one before.

Mine runs on 85 octane without a knock.

I run 87.