5.3 vs 6.2 octane

h2100 said:

Hello All,

I'm an owner of a 2010 Tahoe with 185,000 (middle aged!) and will be upgrading in the next 3-4 months to a new-to-me model. Probably a 2017-2018 Tahoe/Yukon/Escalade. I have a 23 ft boat that I travel with 6-7 times a year plus other trailers many time. The 5.3 does good enough but it does work hard. An Escalade (Denali too) is interesting to me since the 6.2 comes standard.

Question, it seems many web pages/articles indicate the 6.2 needs 92 octane to run properly. Who has experience here?

Is this true?? Please share thoughts.

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Leardriver said:

I like Intheburbs answer.

I ran a dyno in Denver at high altitude. Several absolutes were clear.

In a normally aspirated engine, meaning no turbo or supercharging...
Your octane requirements go down about one point for every 1,000 feet above sea level. If you need 91 at SL, 85 runs the same in Denver.
Run the lowest octane fuel that your engine doesn't detonate on if energy and wallet efficiency matters to you. High octane fuel isn't better fuel, it could be argued just the opposite. It has more additives to resist detonation, and it burns slower. Lower octane burns faster and creates more energy IF the engine can peacefully exist, which at high altitude is virtually always. The argument that 85 octane makes more power than 93 is true-ish, but that's an oversimplification. The tradeoff for high octane burning slower than low octane is a tiny bit less explosive power, but you would never feel it.

We had a dirt bike dyno, and would measure bikes with great smelling 104 octane race gas in the CRF450R, and they would make 2 hp less than 91 octane pump gas. I raced MX for 25 years, and always said that if you want to go faster, twist the throttle. Those bikes make more power than mortals can use.

If you are towing a heavy trailer up the mountains, more octane doesn't hurt for that tank as an extra dissipator of heat. The higher altitude of the mountains, and warmer summer air actually reduces your octane requirements even more, but when you are on the gas non stop on long hills, more octane gives you a cheap source of additional margin.

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intheburbs said:

This is straight out of the owner's manual for my 6.2 Sierra Denali (2009):



Yes, it says you can use 87. I don't. Why? Because the 6.2 is a "high-compression" engine that inherently needs higher-octane gas. And frankly, I don't trust the knock sensors and the computer to be able to adjust the timing well enough to fully control knock/ping. The manual even says that, you might hear a "slight" knock. Using 91+ octane gas is, IMHO, cheap insurance against possible engine/piston damage.

That, plus the fact that when I floor the throttle, I want all 400 ponies present and accounted for.

I'm actually tempted to take it to the other extreme and run E85 in it. If I'm willing to tolerate the abysmal mileage and limited range (10 MPG with a 26-gallon tank), E85 has an effective octane rating over 100.

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mikeyss said:

I'm sorry, but if you're going to buy a premium vehicle that has an engine that requires premium fuel to keep it from pinging or whatever... Than don't be a cheap ass and use the wrong fuel for it because you can't afford it. Don't buy a vehicle that you can't afford to operate properly. I LOVE escalades, but I didn't buy one because I know I can't afford some of the higher end stuff that would eventually break, like the MRC suspension. It really gets me that people buy a 6.2 that is meant to be a upgrade compared to a garden variety 5.3, and then treat it like it's a 5.3 and claim it's ok. High compression engines require better fuel, no matter if you're towing or not. Why buy a premium engine/vehicle if you're gonna just trash it by using inferior shit to keep running it? If you want to use 87 octane in a 6.2, knowing it's gonna make WAY less power because it's adjusting for the shit fuel.... Then why not just buy a 5.3?

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mikeyss said:

Living here in Colorado, I only use E85 in my 6.2. It has more power, but sometimes it takes 2 - 3 extra seconds of cranking to get the engine started.

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Black Limited said:

Your mileage is probably lower also...………...

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Black Limited said:

Your mileage is probably lower also...………...

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swathdiver said:

For a buck thirty a gallon, who cares? LOL

Cents per mile, if the price is right, it pays to burn the stuff. It's also good for the fuel system and the motors love it.

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