Fuel

[SouthernSilveradoGuy85]

I'm not sure if all gas station companies do this, but I saw where a tanker truck driver said that mid grade fuel is just from mixing premium with regular. So to me that makes me think that it may not be the perfect mix every time, meaning not perfectly 50/50. So sometimes you may actually get more premium than regular and other times vise versa. When I had my '14 I started out with 87 and tried 89 up until selling it. I honestly didn't feel any difference. I know it's supposedly fix the tick, but I don't remember 89 doing anything. Seemed to me it just cost about 20 cent more for no advantage. I tried to be positive at first, but I think it was more or less that placebo effect and after a few fill ups with 89 I noticed there wasn't really any difference. I also always go to a big name station, no mom and pop store unless I absolutely had to.

 

Maybe the info I've read is wrong, but I saw that the 5.3 is 11:1 compression.

[VdellaV]

Octane usage is based on compression ratios and timing curves. 5.3 liter can use 87 octane because of it's compression ratio of 9.5 to 1, whereas a 6.2 liter (L86) runs 11.5 to 1 compression ratio. That is why the manufacturer recommends higher octane fuel.

 

 

hmmm I thought 5.3 ran 11.0:1

 

http://www.gmpowertrain.com/engines/5-3l-l83.html

[gone_fishing]

Octane usage is based on compression ratios and timing curves. 5.3 liter can use 87 octane because of it's compression ratio of 9.5 to 1, whereas a 6.2 liter (L86) runs 11.5 to 1 compression ratio. That is why the manufacturer recommends higher octane fuel.

 

Another little factoid, the 10% ethanol blends are great for cold winter start ups but recommended in very hot Arizona weather.

 

The EcoTec3 5.3 (L83) is 11.0:1

[Motor City Rick]

In my research I see the dramatic increase with the 5.3L (L83) compression being 11.0 to 1 which would require 93 octane. But the majority of 5.3's out there are running the 9.5 CR. I guess my action would require me to read the current owners manual.

 

Starting with different sites:

 

9.5 at this site: http://www.kgbanswers.com/what-is-the-compression-ratio-on-the-53-liter-chevy-v-8-engine/1562128

 

9.5 / 9.6 at this site: http://www.hcdmag.com/53l-vortec-engine/

 

9.6 at this site: http://gmauthority.com/blog/gm/gm-engines/lmg/

 

11.0 at this site:http://gmauthority.com/blog/gm/gm-engines/l83/

[VdellaV]

In my research I see the dramatic increase with the 5.3L (L83) compression being 11.0 to 1 which would require 93 octane. But the majority of 5.3's out there are running the 9.5 CR. I guess my action would require me to read the current owners manual.

 

Starting with different sites:

 

1.- 9.5 at this site: http://www.kgbanswers.com/what-is-the-compression-ratio-on-the-53-liter-chevy-v-8-engine/1562128.

 

2.- 9.5 / 9.6 at this site: http://www.hcdmag.com/53l-vortec-engine/

 

3.- 9.6 at this site: http://gmauthority.com/blog/gm/gm-engines/lmg/

 

4.- 11.0 at this site:http://gmauthority.com/blog/gm/gm-engines/l83/

 

 

1, 2 and 3: Gen 3 and 4 5.3 liter engines

 

4: New Gen 5 L83 Engine

 

My guess is that since 5.3s are mostly meant for work trucks, they are tuned with lower timing to be able to use 87-89 octane, while 6.2s are more focused on performance. Thats true at least for Mexico, here you can only get the 6.2 L86 Engines on the Premium Cheyenne Packages and GMC Trucks

 

[SouthernSilveradoGuy85]

In my research I see the dramatic increase with the 5.3L (L83) compression being 11.0 to 1 which would require 93 octane. But the majority of 5.3's out there are running the 9.5 CR. I guess my action would require me to read the current owners manual.

 

Starting with different sites:

 

9.5 at this site: http://www.kgbanswers.com/what-is-the-compression-ratio-on-the-53-liter-chevy-v-8-engine/1562128

 

9.5 / 9.6 at this site: http://www.hcdmag.com/53l-vortec-engine/

 

9.6 at this site: http://gmauthority.com/blog/gm/gm-engines/lmg/

 

11.0 at this site:http://gmauthority.com/blog/gm/gm-engines/l83/

 

Well the 2nd link is talking about the Vortec, the '14+ 5.3s are called Ecotech3 So the ones you see in the mid 9s:1 compression are probably talking about the pre '14 5.3, from '99 up to '13. The Ecotech3s are a new design. So not all 5.3s are the same. Same as the Vortec 350 that was in my '98 isn't the same as my carbed 350 in my '83.

[gone_fishing]

All the Gen 5 EcoTec3 motors are direct injection which is suppose to allow for higher compression ratios without using high octane fuel. I'm sure there are other technologies used that allow the use of 87 octane with 11.0:1 compression. Mazda has a gas engine that has a 13.0:1 compression ratio and runs on regular.

[Mervkirwin]

Hello, just wanted to say thank you to everyone for the good info on what gas to use in the 6.2l. Thanks again and be safe everyone.

[HondaHawkGT]

This is what Justin of Blackbear Performance had to say on the Ecotec3 5.3:

 

"At 11:1 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.

 

 

 

GM doesn't recommend any higher than 87 because they know that a) they will be vilified for doing so by consumer reports, motor trend, car and driver, etc and b) they know that people won't listen."

 

I run 91 in the summer and 89 in the winter.

[Black02Silverado]

This is what Justain of Blackbear Performance had to say on the Ecotec3 5.3:

 

"At 11:1 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.

 

 

 

GM doesn't recommend any higher than 87 because they know that a) they will be vilified for doing so by consumer reports, motor trend, car and driver, etc and b) they know that people won't listen."

 

I run 91 in the summer and 89 in the winter.

Justin is the man. With him in the tuning business I'm sure he see's a ton of what goes on inside these vehicles ECM's and how low octane fuel performs. Not to mention, with 11:1 compression, back in the day of carborated you didn't run anything but 93 or higher or it would knock like a woodpecker on an oak tree full of ants. I'm sure modern tech makes things better but plain and simple and anyone with internal combustion knowledge knows the damage "knock" can cause. Also, if anyone is old enough to remember fuel back in the 60's was a higher octane than today thanks to having lead in it.

 

Don't forget the powertrain warranty was lowered from 5yr, 100,000 miles to 5yr 60,000 miles.