Towing a 4600 lb trailer

[jagabom (Esquire)]

Have a 2011 Sierra 5.3 - 6 speed auto with AFM disabled.  Any advantage using number 1 (premium) gas to tow?  

Jim

[greatmizzou]

No.   I would avoid 85 octane tho in the mountains and stick with 87

[swathdiver]

You get better mileage with high octane gas, more timing advance for more power.  I've even towed while burning ethanol, you can watch the gas needle move...  

[intheburbs]

If you have a flex-fuel engine, you would see a power bump running E85, but also a big-time drop in mileage. 

 

Not sure the 5.3 is even programmed to take advantage of premium gas, so I question whether you'd see any bump in mileage or power without a custom PCM tune.  I did do a "hot" tune on my 2001 Suburban, trying to get a little extra when towing our 4500-lb RV.

 

On 1/5/2020 at 8:27 PM, greatmizzou said:

No.   I would avoid 85 octane tho in the mountains and stick with 87

The reason you can even buy 85 octane in high-altitude states like Colorado is that the thinner air makes 85 octane behave the same as 87 at sea level.  85 octane won't hurt a thing.  I lived in Colorado for 10 years, have a little bit of experience driving in high altitudes.

[greatmizzou]

57 minutes ago, intheburbs said:

If you have a flex-fuel engine, you would see a power bump running E85, but also a big-time drop in mileage. 

 

Not sure the 5.3 is even programmed to take advantage of premium gas, so I question whether you'd see any bump in mileage or power without a custom PCM tune.  I did do a "hot" tune on my 2001 Suburban, trying to get a little extra when towing our 4500-lb RV.

 

The reason you can even buy 85 octane in high-altitude states like Colorado is that the thinner air makes 85 octane behave the same as 87 at sea level.  85 octane won't hurt a thing.  I lived in Colorado for 10 years, have a little bit of experience driving in high altitudes.

I hear ya, thats been like that for ages.  From experience in towing my camper in my old 5.3 2002 1500, my engine was pinging like crazy with 85 and that was up in the mountains near cripple creek and divide.  I swapped to 87 and no more pinging.    Maybe it was a combo of me having intake leaks but for sure it wasnt performing same as flat land 87.