Octane question

[oujeremy]

Did a quick forum search and didn't immediately find what I was looking for so I started this thread. Mods feel free to merge, etc as needed.

 

I just bought a 2014 Denali which I drive for work and personal use. Using higher octane fuel is a no-brainer for the 6.2L V8 in my opinion, but my employer provides me with a fuel card and doesn't like seeing anything but 87 octane on the bill.

 

What are the effects of 87 octane fuel gong to be on my engine both short and long term? Thanks in advance for everyone's input.

[HondaHawkGT]

Less power and potentially bad fuel economy.

 

Quote:

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At 11:1 [11.5:1 for the 6.2] compression ratio (DI or otherwise) the engine *cannot* efficiently run 87 octane under any circumstances. As a result, knock occurs (heard or unheard) and the ECM retards ignition timing both immediately and long term. The result is reduced fuel efficiency (sometimes as high as 3-4mpg) and considerably less power output than would be seen on 89 octane. You won't notice this power loss under light throttle though due to the ECM's method of controlling throttle angle... essentially, the throttle will be opened more for the same power output target on 87 as 89 so that it feels exactly the same to the driver.

 

In terms of ignition timing, where 18-19 degrees of advance might be the target by GM under the factory tuning, on 87 octane, that timing drops to under 10 degrees of advance to prevent knock from occurring (in response to knock that has already occurred). Anybody that has dealt with ignition timing should see this as a very poor situation. The knock retard occurs early and quickly and then the lasting effects (octane scaler blending the high and low octane tables) will stay in effect for dozens of miles before decaying out.

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[glcbn]

I would offer to pay the difference in fuel cost. No way I would skimp on octane with a 6.2. I have never run 87 in my 5.3. Actually 87 shouldn't be used in any of the new high compression engines. GM doesn't state it in the manual per say, because as posted in other threads people wouldn't listen anyway.

[TJay74]

Actually the manual on the 6.2l states premium is require and potential damage can occur of continued use is used. I wouldn't run anything less than 91 in the truck no matter what my employer states, unless they are going to put in writing they will pay for the damage to the vehicle that could potentially happen from running lower octane fuel.

 

When I got my 2016 truck with the 6.2 the dealer put 87 in it, I raised the flag and they played dumb about it. You could hear it pinging off of the side of the crash barriers if you got into the throttle.

[glcbn]

Actually the manual on the 6.2l states premium is require and potential damage can occur of continued use is used. I wouldn't run anything less than 91 in the truck no matter what my employer states, unless they are going to put in writing they will pay for the damage to the vehicle that could potentially happen from running lower octane fuel.

 

When I got my 2016 truck with the 6.2 the dealer put 87 in it, I raised the flag and they played dumb about it. You could hear it pinging off of the side of the crash barriers if you got into the throttle.

 

TJay I should have clarified a bit. The 5.3 manual doesn't have any text about using higher octane.

[ic3man5]

From Black Bear Performance's FAQ:

 

For an inclusive (but not fully-encompassing) list of all vehicles that can run 87 but should not (under any circumstances), see below:

• All LS1, LS2, LS3, L99, LS7, LSA, LS9 equipped vehicles. 91+ octane required.
• 2005+ L33 "B" engine silverado/sierra models. With a higher compression ratio than the standard 5.3L for those years, 89 octane or better is recommended for both fuel efficiency and power output.
• 2007+ 5.3L engines. At 10:1 compression, this engine (all variants) cannot run efficiently on 87 octane. Power output and mileage will be noticably better in 95%+ vehicles simply by switching from 87 to 89 octane. 91+ preffered.
• 2001-2007 LQ9 vehicles (AWD Cadillac Escalade, Silverado SS, Sierra Denali, Vortec Max). Compression ratios (and owners manual) dictate that premium fuel should be used at all times.
• 2007+ 6.2L L92 (and variant) vehicles. All 6.2L truck/SUV engines have a 10.5:1 compression ratio and as a result, require premium. Most of these vehicles will have a note in the owners manual as well as a decal on the gas door stating a recommendation to that effect.
• All 2014+ direct injected vehicles. Compression ratio is simply too high to efficiently burn 87 octane.

 

[emeryz28]

I usually run 91 octane. the other day I was at a station that had only 89 or 94....weird right. Anyway I gave 89 a chance and noticed no difference in performance or MPG

[HondaHawkGT]

89 vs 91 is minor for a stock truck. The 5.3 runs terrible on 87, especially in the summer when the ac is running and I'm hauling a decent amount. You can feel the computer pulling timing.

[Rock1500]

89 vs 91 is minor for a stock truck. The 5.3 runs terrible on 87, especially in the summer when the ac is running and I'm hauling a decent amount. You can feel the computer pulling timing.

I switched to 89 recently but to be honest I barely noticed an issue with 87.

 

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[jagabom (Esquire)]

I run 89 just because of the higher compression ratio.

It is in the order of 11 to 1. 4.3 V6 91 is just a little too expensive

Jim

[tnchevy]

GM recommends 87 for a reason. I have ran tanks of both 87 and 89 multiple times with no difference in noticeable power or gas mileage. Just because this compression numbers for this engine is high does not mean it has to have a higher octane. This engine is DI and of course liquid cooled and naturally aspirated which all factors in to what octane the engine can run. I've got a couple of air cooled motorcycles with similar compression ratios that do require 91 or higher octane but these bikes have the computer power of a 1982 datsun with no oxygen sensors.

[TJay74]

GM recommends 87 for a reason. I have ran tanks of both 87 and 89 multiple times with no difference in noticeable power or gas mileage. Just because this compression numbers for this engine is high does not mean it has to have a higher octane. This engine is DI and of course liquid cooled and naturally aspirated which all factors in to what octane the engine can run. I've got a couple of air cooled motorcycles with similar compression ratios that do require 91 or higher octane but these bikes have the computer power of a 1982 datsun with no oxygen sensors.

 

 

While GM puts in the manual that the 5.3l trucks can run 87 octane, testing from multiple people myself included has shown that the 5.3 engines will show spark knock almost all the time, it gets worse when the weather gets warmer outside. While he engine can handle since the ECM drops into a low octane timing table to reduce timing, it also causes power loss as well.

 

It costs maybe $4 per tank to run premium, so the cost is worth it in my eyes. Being that I have a 6.2 I run 91 all the time, I now have access to 100 octane as well so I calculated the ratio needed to get to 93 octane and will run it at times as well.

[oujeremy]

Firstly, thanks for the replies. I can tell I am going to like this forum.

 

After consulting the manual further and noticing a message on the fuel cap it's been determined that 91 octane (or higher) is the way to go. I showed my employer the necessity and they have agreed to pay for it. Actually found a Shell station that sells 93 octane. The 6.2L V8 runs and rumbles like a beast unhinged on that stuff.

[harveyfamily]

I'm now on tank 3 of 89 after the dealer fill of 87 when I purchased it. I didn't see a difference in power or mileage until the 3rd tank of 89. Before I would average 15.5-16.5. On this 3rd tank of 89 I'm averaging 19-19.5.

 

Does anyone know of the 2015 Traverse 3.6 V6 is also DI? Should I start running 89 octane it it too?

[glcbn]

I'm now on tank 3 of 89 after the dealer fill of 87 when I purchased it. I didn't see a difference in power or mileage until the 3rd tank of 89. Before I would average 15.5-16.5. On this 3rd tank of 89 I'm averaging 19-19.5.

 

Does anyone know of the 2015 Traverse 3.6 V6 is also DI? Should I start running 89 octane it it too?

 

Pretty sure it's 11.3 : 1 compression ratio. Sure couldn't hurt to run a higher octane fuel.