6.2 vs 5.3 and premium gas

[PatDTN]

I'll join in. Yes the power of the 6.2 is addictive. That said for some reason - possibly the strong iron block - most people building race or high performance engines are choosing the 5.3. Maybe before swapping to a 6.2 see what gains can be made on a 5.3 before it too needs premium fuel.

 

[Stbentoak]

My wife’s previous vehicle needed premium… put in 87 and it would throw a CEL. Switch back to premium CEL went out…all I need to know….

 

[Erik23]

I wasn’t even considering the 5.3 personally. The 6.2 is more powerful and the 3.0 gets better mpg so it’s kind of like what’s the point unless money is a big issue.

 

[SSGUNNER]

Just for sh&*$ & giggles but what would be the cost of swapping the L84 for the L87? Would you need to change anything else? Both use same tranny perhaps suspension.

Ive seen new 5.3's on sale for less than 8k if not much less. Just curious, wouldn't do this myself but bet someone out there would.

 

[SSGUNNER]

I'll join in. Yes the power of the 6.2 is addictive. That said for some reason - possibly the strong iron block - most people building race or high performance engines are choosing the 5.3. Maybe before swapping to a 6.2 see what gains can be made on a 5.3 before it too needs premium fuel.

Funny, I was actually thinking about something like this earlier as I was driving and what potential the 5.3 has.

 

[Campingfamco]

I had the 5.3 in my 2016 and the only reason I sold it was because it was constantly hunting for gears in the mountains. This time around I said I won’t get anything but the 6.2 and I’m so glad I did. The power fits the vehicle properly. The 5.3 is too under powered for the size of the truck. If you’re paying this much for a car you will be able to afford the extra it costs to fill up the tank.

 

[swathdiver]

Higher octane fuel such as premium has nothing to do with energy content or quality. It is a measurement of the gasoline's ability to resist engine knock. Engines that have a higher compression ratio need a higher octane fuel too prevent knock. So too make a long story short you can use a fuel with a low octane as long as your engine is not knocking. I highly doubt you will get knocking in a stock 6.2 engine with a quality top tier brand selling 89 mid grade. My Corvette calls for premium and runs fine with 89 mid grade.

I have 100,000 miles on. 6.2 that has seen mostly 87 octane other than when pulling heavy loads and had 0 issues at all. I routinely get 23 mpg highway with it. If you want most performance run premium if not no worries running 87.

Remind me not to buy a car from either of you two!

Knocking and pinging can rarely be heard these days fellas. With the AC and stereo going, wife yakking away and those glorious V8 sounds, you really need a scan tool to see the knock detectors going off and pulling the timing. There are lots of videos on youtube and posts on these forums that attest to this. To each his own, it's your money and reputation.

 

[91RS]

Remind me not to buy a car from either of you two!

Knocking and pinging can rarely be heard these days fellas. With the AC and stereo going, wife yakking away and those glorious V8 sounds, you really need a scan tool to see the knock detectors going off and pulling the timing. There are lots of videos on youtube and posts on these forums that attest to this. To each his own, it's your money and reputation.

Exactly what I thought as soon as I read those posts. It isn't knocking like a rod knock or even the failed lifter noise. It is spark knock or detonation and you generally won't be able to hear it unless you turn the radio off, HVAC off, windows up, no talking, quiet road, etc. and then load it up like going up a hill or grade and giving it as much throttle as possible that will not take the TCC out of lock up. Run premium or buy a 5.3L. If $5-$10 extra per fill up breaks you, you don't need to be buying a new car anyway.

 

[George B]

From all the reading I have done on here since I joined I have learned that even the 5.3 leaves power on the table when you run 87. I know the seat of the pants meter proves it with mine. I imagine it’s the same with the 6.2.

 

[Geotrash]

I have two 6.2L Yukon XL Denali’s and both of them only see premium fuel. If cost were my primary concern, I wouldn’t have 6.2’s. I like the power, also keep my cars for a long time, so power and durability are my primary concerns. They may not be yours, and that’s okay, but you’re incorrect if you believe that running 87 doesn’t do any harm to the engine. I also do care that whoever owns my vehicles after I do will share in the benefits of the proper care I’ve given them.

Watch the video that @swathdiver posted. The truth about what kills 6.2’s is evidenced in the post-failure tear downs. Yes, you can run 87 for a while and the ECM will adjust the timing to reduce pre-ignition. But it’s not a perfect system, and it’s still happening even if you can’t hear it.

The pistons in these engines are hypereutectic aluminum-silicon alloy, and they accumulate fatigue over time. There are multiple studies that show the failure properties of these alloys, and these explain why some people have failures and others don’t. Because they are cast, they contain microscopic pores of varying sizes. The larger the pores, the more likely that piston is to crack. When pre-ignition occurs - even if it’s caught by the knock sensors - the piston experiences many times the internal cylinder pressure (ICP) as it would running normally. Higher ICPs = more fatigue. If one or more of your pistons has pores larger than average, your failure will come sooner.

What it means is you’re taking your chances running 87 in a 6.2. You might get away with it for 100,000 miles, or you might not. But you’re several times less likely to see 200,000 miles on 87 because of the way the piston alloys accumulate fatigue. The engineers who designed the 6.2 know this as well, which is why they recommend premium fuel.