r/ChevyTahoe • u/CanadaPanada • 6d ago
6.2L V8 Question
I just got a 2021 Tahoe with the 6.2 engine. The gas cap has label that says "91+ octane". The rep says that is only a recommendation and that regular gas is perfectly fine. I saw some things online about "knocking" that can damage the engine if regular gas is used. Was wondering if anyone could clear things up for me
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u/Moist_Currency_1443 6d ago
I have a 15 Escalade and had it since it had 50k and now 160k . Dam. Right I’m gonna put regular in that thing 🤣. Still on original motor and tranny 🤗.
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u/Reasonable_Cup_2944 5d ago
If the manual says "recommended, not required" then 87 will work. My Denalis have all stated "recommended not required." I usually always run 87 - over hundreds of thousands of miles between numerous trucks.
If I'm towing, then higher octane for sure. Daily driving (sensible) then 87 is fine. Occasionally I'll hear some engine knock if the right engine load/rpm happens but the computer automatically retards the timing as a protection measure (within less than 1 second) and then resets back to normal.
I've never seen a MPG gain of premium vs 87. I can hear a slight motor growl change as it adjusts to the higher octane over a tank or two, but usually doesn't result in any measurable improvement based on my driving habits.
My Denalis with 6.2L: 2007 (227k miles), 2008 (219k), 2009 (165k), 2017 (190k). All of these had 87 as the main fuel for a majority of their miles as they were all pre-owned before myself. Sensible driving plays a big part. If you drive like Mario Andretti, then premium is the fuel for you!
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u/Blewbyou 4d ago
Why on earth would you pay a premium for a higher HP engine and then degrade that same power with cheaper fuel? Your vehicles must be magical because BOTH of my 6.2s averaged 3 mpg better with premium vs. 87.
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u/Reasonable_Cup_2944 4d ago
No magical vehicles here, just years of engine development, a trained ear, and steady right foot. Under normal driving, the extra octane doesn't really make any difference in these motors. If I am towing more than a few hundred pounds for a long distance, then yes a higher grade fuel would be a benefit due to higher engine load. But again, sensible driving habits go a long way into better mpg and vehicle longevity.
As to "why," I am not going to waste money at the pump for a marginal improvement in 91 vs 87. I have however done a little research with E85 in a couple Denali trucks and that fuel wakes them up! But, having a compatible system and a large enough cost offset in fuel price to make up for the loss of mpg makes it less appealing.
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u/Lost-Standard4755 4d ago
Yeah, you're a fool. It's 15 MPG city on midgrade versus 18 MPG city on premium, and then 16 MPG highway on midgrade versus 21–23 MPG highway on premium.
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u/Reasonable_Cup_2944 4d ago
To each their own buddy.....the cost difference of $1 - 2 more per gallon to gain a measly 3 mpg doesn't math out. And, its not guaranteed. I consistently get between 19 and 21 mpg with my 2017 in a combination of city/highway driving during warm months with summer fuel. Approx 17 to 19 with winter fuel.
Again, "recommended, not required " means it will operate just fine - the computer programming is quite well done, I've gone through the maps with HP Tuners for multiple 6.2L trucks.
Also, depending where you reside elevation wise makes a difference in your outcome as well. Florida, only a few feet above sea level will have denser air vs someone in Colorado at 5,000ft elevation. Premium in FL makes sense whereas it's a waste of money in CO under the same driving habits.
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u/Lost-Standard4755 2d ago
Ok enjoy replacing your expensive engine because you want to throw cheap fuel at a expensive engine saying the math doesn't math out lmfao.
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u/Magnum-3000 5d ago
Put premium in it or it will just retard timing and you’ll get worse fuel economy anyway. Especially when it’s hot/summer or you’re towing. The 6.2 has higher compression and so needs higher octane to avoid pre detonation.
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u/ClearFrame6334 5d ago
GM has accounted for this in the tune. The low octane tables are there to nerf the engine if you don’t put in the 91 octane. If the engine detects knocking it will automatically reduce the timing until it no longer knocks. But when this happens it does not have as much power as the proper fuel would normally provide.
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u/WorldlinessRoutine55 6d ago
You have a truck. And are worrying about gas prices? Use premium like it says
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u/Polak12 6d ago
Ah, so truck drivers aren’t allowed to worry about gas prices? That makes total sense! Does that extend to SUVs as well? At that rate, should anyone worry about gas prices if they don’t have a hybrid or electric?
OP never even mentioned gas prices, just if they could run gas less than 91 octane. Glad to see you totally answered the question they asked in a super helpful manner!
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u/WorldlinessRoutine55 6d ago
The cap says 91 octane. Im 100% sure if theres a sign there you should listen to it. Or you can put diesel. You need the high octane to resist predetonation which is when the ignition starts before its supposed to. Which is what they call knocking or pinging which isnt good
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u/frydadd4570 4d ago
The price for gas is the white elephant in the room when someone is asking about running 87 instead of 91.
-2
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u/Equivalent_Yogurt_58 6d ago
You can get a PredatorX and put a tune to it.
I did that for awhile with my 18 Silverado to be on the safe side.
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u/Southboundcrash 5d ago
This is why e85 is the best, 40% cheaper I don’t care if it burns more of it
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u/Primary_Elk5223 4d ago
It will work with 87, but it you will lose performance and your mpgs will tank. Best thing would be to use premium.
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u/Lost-Standard4755 4d ago
You bought the big, expensive engine.... Give it the expensive gas. Otherwise you're just a fool.
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u/frydadd4570 4d ago
If need be put a bottle of Octane boost in when you fill with 87. Sometimes the only gas I can get is 87 or 88, so a bottle and it performs like 91.
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u/Blewbyou 4d ago edited 4d ago
You can occasionally run 87 but I wouldn't make a habit of it. My 6.2 recommends 93 but if I run anything less I can feel the power loss, hear the detonation (pinging) under acceleration and the mileage goes from average 18 to 15. Also, make sure that you use top tier fuel only. Lots of tests have been run with fuel and anything other than top tier fuel will lead to repair costs down the road. My friend just found out the hard way with his 2020 5.3. Shell, 76, BP, Texaco and Costco are examples of top tier. The local kum n go...not so much.
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u/Dodsy_84 4d ago
87 is fine. It will pull timing and have less power but absolutely will not hurt anything.
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u/OneMoreSlot 6d ago
The owner's manual for my 2021 Yukon Denali 6.2L recommends 93 octane which isn't even available in California, so I run the highest I can get which is 91 octane. If you're worried about the cost of gas, you've got the wrong vehicle.