87 Octane in 6.2L

[captras]

Before somebody starts ranting and raving about being a cheapskate, this was done only out of curiosity! My last fillup was with 87 Octane. I have used 93 since the truck was new but wanted to see if there was any performance/mileage difference. Mileage difference was very little, if any. Back and forth to work, 36 miles RT, I still saw 19-20 MPG. I did notice some performance drop when accelerating hard, but it still was a beast. I dont think I would ever consider 87 if I were towing, and after this tank, I will go back to 93....its only about $6.00 difference in a fillup. I was curious because I have a 2003 Vette, and the difference was quite pronounced in that car....2-3 MPG difference. I expected a drop, but didnt notice one with the Silverado. Still, probably the BEST vehicle I have ever owned!

[Stevens03]

I ran 89 in my 6.2 without issue. Its a good compromise without any issues. Like you stated there was a little performance difference but not enough to worry about.

[Isriam]

you'll get taken to the woodshed on this forum for running 87/89 in your 6.2

 

i ran 87 for 5,000 miles with no problems. i just started running 93 because the owners manual says basically you must run it, and i figured if i had any warranty claims i better not have it denied due to something so stupid.

[Vanished]

I thought it stated you should run 93 but can run 87 if it doesn't knock?

 

 

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[servantsalesmen]

You need to run high octane fuel in order to avoid pinging. The 6.2 has a high compression ratio and the more you crush gasoline in a cylinder, the more unstable it gets. The octane keeps the fuel from igniting without spark. Lower octane fuel can ignite just from being compressed too far. I'd stick with the 93 if I owned a 6.2.

[glcbn]

 

Mileage difference was very little, if any. Back and forth to work, 36 miles RT, I still saw 19-20 MPG. I did notice some performance drop when accelerating hard,

 

Same deal with my 5.3L.

[gone_fishing]

This is from the manual says regarding fuel for the 6.2

 

If the vehicle has the 6.2L V8 engine (VIN Code J), use premium unleaded gasoline with a posted octane rating of 91 or higher. Regular unleaded gasoline rated at 87 octane or higher can be used, but acceleration could be reduced, and an audible knocking noise may be heard. If the octane is less than 87, a heavy knocking noise may be heard. Use 87 octane rated gasoline or higher as soon as possible. Otherwise, the engine could be damaged. If heavy knocking is heard when using a higher octane rated gasoline, the engine needs service.

 

I have the 5.3. I've had my scan gauge hooked up basically all summer monitoring timing and knock retard (KR). A few observations I've noticed when trying different fuels.

 

With 87 and even 89, there can be quite of bit of KR when in V4 mode. I've seen up to 4-5 degrees of KR reducing total timing to only a few degrees advanced before the engine will kick out of V4 and go back to V8. This scenario usually happens if you are going up a slight hill or going into the wind. Basically anytime that you are in V4 and the load increases on the engine, this is where I see KR. Even without any steady KR, I don't really see more than 7-10 degrees of timing advance on the lower octanes.

 

91 octane (no 93 around here) seems to reduce this V4 KR quite a bit. Maybe pickup a little every now and then but not as much with 87.

 

On E85 I experience basically no KR. Engine stays in V4 for a lot longer too (can go up slight grades or go into the wind easier in V4). Total ignition timing advance can be as high as 15 degrees easily (approaching 20+ if you have a tail wind). I can only assume the higher octane is making the difference with E85. Of course this isn't applicable to the 6.2 since they are not E85 compatible.

 

With any fuel, KR doesn't seem to be a problem in V8 mode. Even WOT runs I really don't pick up any (maybe 1 or 2 but it falls off quick).

 

Long story short, the engines seem to prefer higher octane. With the 11:1 compression on the 5.3, I can only imagine that the 6.2 is even pickier with 11.5:1 compression.

[gone_fishing]

Removed double post

[svltrack]

On a non-emissions controlled vehicle (all things equal), more power would come from 87 octane versus 93 octane.

 

Octane is gasoline's measure for how quickly it will burn/expand. As your spark plug fires a front of expansion goes across the combustion chamber; the higher the octane the longer this takes.

 

Today's computer algorithms are smart! (so are the engineers) They use the amount of ping (detonation), o2 in the exhaust, MAP and several other variables to determine the best way to make power while not putting undue stress on the components.

 

I would suggest running 91 or 93, but if you are in a pinch as the other post mentions your truck will fix the difference in octane by changing the ignition timing as needed.

[f8l vnm]

Wow and I though 87 would do. Guess 91 it is for better efficiency

[OhmMega]

Octane has nothing to do with power or efficiency.

 

In layman's its the length of the fuse on a firecracker.

 

Want to chance bending rods or having a sluggish engine while the computer compensates for detonation? Put a low octane fuel in an engine designed for high octane.

[BigBadSierra]

At least most of you don't have to deal with the ethanol blends we have to deal with here in Canada . All 87 gas is blend here. I run 91 Octane just to avoid the ethanol blend and can pick up 1.5 to 2 mpg.

 

The blends suck the millage down. Add in winter gas and you can lose 3 or more mpg depending on the Vehicle.

 

So I gas up at Costco with 91 because I know there is no Ethanol in it.

[KARNUT]

This thread is amusing, the amount of money that is spent to even get the 6.2, then not spend a couple bucks more for 91-93 fuel, really? One less trip to starbucks.

[redwngr]

At least most of you don't have to deal with the ethanol blends we have to deal with here in Canada . All 87 gas is blend here. I run 91 Octane just to avoid the ethanol blend and can pick up 1.5 to 2 mpg.

 

The blends suck the millage down. Add in winter gas and you can lose 3 or more mpg depending on the Vehicle.

 

So I gas up at Costco with 91 because I know there is no Ethanol in it.

Not all Canadian high test is ethanol free.

 

When ethanol blends first became available, (a long time before mandatory blending) Sunoco high test was one of the first places it was blended. I have no idea if they use it now.

[Higgs Boson]

At least most of you don't have to deal with the ethanol blends we have to deal with here in Canada . All 87 gas is blend here. I run 91 Octane just to avoid the ethanol blend and can pick up 1.5 to 2 mpg.

 

The blends suck the millage down. Add in winter gas and you can lose 3 or more mpg depending on the Vehicle.

 

So I gas up at Costco with 91 because I know there is no Ethanol in it.

 

Actually everything here is a blend, even premium 91 or 93....there are a handful of stations that still offer ethanol free in the entire country. It is basically all 10% ethanol with a push to E15 and there are more E85 pumps than E0.