Octane and Towing
 

I’m in a discussion with a guy about octane and towing. Up until last week, I had a 2015 Silverado with 5.3 Direct Injection. When I would tow my Chevelle in my 24’ enclosed trailer, I would run high octane because the engine is working harder.

I realize the timing will adjust to prevent engine knock but my thought, and the way it was explained to me, is that the higher octane will prevent detonation. If that’s the true, the timing won’t back off which in turn will help prevent power loss.

Am I way off........too old school??? :dunno:

Kurt

Get a diesel and lower your octane!

I agree. When towing heavy loads I often fill up with hightest. No need to reduce timing and power with higher loads.

These engines are tuned so lean for federal emissions, that they are always on the ragged edge of detonation. Keep doing what you're doing.

I upgraded to a 2016 with a 6.2L, 8-Speed, 3.42 rear with Max-Towing Package. What a difference this setup is compared to the 5.3L, 6-Speed with 3.42 rear.

I can tell you from experience that if you run junk, low octane gas when towing you will definitely get detonation. I had it so bad once it activated the knock sensor on the motor.

Rich

Octane & towing
 

Congrats! You will love it going forward. On the Octane / Towing question, I've owned a Gas Station for the past 33 years and this question comes up a lot. My experiencen is that increasing the octane on any late model computer controlled vehicle will more times than not work against you. Vehicles today are pre-programmed to deliver timing and fuel @ the octane recommended. When you increase octane, the computer will not adjust. Higher octane makes for a slower burn, not faster as most people think. When higher octane is put into a vehicle designed to run on lower octane it will experience longer cranking upon start up, harder starting when hot, and less performance overall. Don't waste your money.

The only time a higher octane will increase performance in an engine designed to run on a lower octane is when an engine has a high carbon build up on the pistons and combustion chamber resulting in essence raising the compression ratio. We use GM top engine cleaner to clean engines when this occurs. Late model GM 3.6 V-6's are common with this condition. It will cause the check engine light to come on for a random or cylinder misfire codes.

Hope this helps, ENJOY your new ride! Feel the power!

Bill

I respectfully disagree on it being a waste of money.

My wife has a 2011 Denali with the 6.2. It really is a great set-up. I can only imagine it is even better in 2016. I thought here owners manual said to run premium fuel. Maybe she is waster her money since I did not confirm what the manual says about fuel, but I can't say we're experience any of the negatives listed above.

This could get into a log debate, but on the dyno you can absolutely push the limits of timing with higher octane. If you actually look at the timing maps programmed into the PCM, they vary for tow mode and regular, and have a range of retard once the knock threshold is crossed. Better fuel will let you stay in the more powerful part of the timing map when pushing the engine.

Granted, light load, modest throttle and the higher octane will not be nessisary on many engines. My experience towing with the Chevy V8 is the better octane is worth it.

Octane and Towing
 

I do not know what GMC recommends for grade of fuel in a 2011 Denali, but my 2015 Denali XL must run on Premium according to GMC. I agree on a Dyno when the timing can be adjusted, it will increase performance, but in a stock programmed ECM in a late model vehicle timing is set by the factory programming and increasing octane will not help performance, only hurt the drive ability. FWIW, That's my opinion / experience. I make more money on Premium than I do on regular so I hope everyone buys Premium. Not trying to be a know it all here, but in my world it's just a waste of money unless required by the manufacture. Once again, ENJOY the new ride.

Bill

Thanks for the replies guys....much appreciated!!!!

I would've thought that higher octane fuel lets the motor run max timing without fear of detonation or killing power when pulling timing out. BTW, anybody else remember the story about the loose, dry trailer ball rattling around in the trailer hitch and triggering the block sensor into thinking the motor was in detonation? Crazy stuff!