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Discussion Starter · #1 ·
So I just got back from a trip across the pass and was suprised by the fuel economy I got, or lack there of. Maintaining a moderate speed of about 65mph towing a 1600lb flatbed trailer with 2 ATV's and the truck loaded with gear I got 9-10mpg. The trailer and gear I would say about 3000lbs combined.
Last summer I made the same trip but at the time I had a smaller trailer that I would say was about 450lbs, but the same ATV's and gear. That trip I averaged between 12-14mpg. The truck had the lift, same tires and wheels, the only changes being the muffler, intake, and programmer (set at 91 octane). Am I crazy to think that my fuel economy shouldn't have changed that much? My fuel economy has never been great around town unloaded I was getting about 9.3mpg and after the changes (intake,programmer,exhaust) that has increased to about 10.8mpg. I don't drive much on the highway, but I usually get about 17-18mpg. Thoughts?
 

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In a word: Yes. In a senence: Yes, towing affects you MPG that much. You're also probably filling up with winter blend fuel with a higher ethanol content so it'll also lower your mileage. When we tow a 4,000lb camper with my brother's '05 laramie, we average 9mpg heading over the rockies to BC.
 

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Discussion Starter · #3 ·
Well that makes me feel a little better knowing that is about the same as what you get. . I knew that the winter blend would lower the mpg, but not that much.
 

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Did it have a gate/ramp that was in the "up" position, catching a lot of air? These create a huge amount of drag. It's actually usually harder to pull and EMPTY utility trailer (with gate/ramp "up") than a loaded one. The loaded trailer cuts the wind better.

Also, you were towing with the 91 performance tune? You should not do this. First off it can damage the engine. I bet your knock sensors were hearing pinging and retarding timing, and that hurts power so maybe that's part of the problem. If you want to tow with a performance tune you need to use higher octane that the tune calls for. When I tow I use the 87 performance tune on 91 or 93 octane. Or you could always do the stock or tow tunes.
 

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Discussion Starter · #5 ·
Did it have a gate/ramp that was in the "up" position, catching a lot of air? These create a huge amount of drag. It's actually usually harder to pull and EMPTY utility trailer (with gate/ramp "up") than a loaded one. The loaded trailer cuts the wind better.

Also, you were towing with the 91 performance tune? You should not do this. First off it can damage the engine. I bet your knock sensors were hearing pinging and retarding timing, and that hurts power so maybe that's part of the problem. If you want to tow with a performance tune you need to use higher octane that the tune calls for. When I tow I use the 87 performance tune on 91 or 93 octane. Or you could always do the stock or tow tunes.
Yes the rear mesh gate was up, I was going to tow with it down but we left sooner than expected so I didn't have time to secure it down. I know it will create more drag and that possibly could be the issue. I plan to tow with it down next weekend so hopefully ill see better results.

Yes I towed with the 91 tune but I run 92 octane, as thats what we have here. If I was running 91 octane, it was 90 degree's out and I was towing a 8,000lb trailer then yes I would definately set it back to the stock tune (or 87 and run 89) but it was only 3,000lbs, 32-40 degree's out and I run higher than required octane.

I actually got better fuel economy towing up the pass than I did down the other side and the next 35miles of mostly level roadway. Maybe it was the fuel at the station that I filled up with mid way.
Thanks.
 

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Ok, I'd still bet that with a few thousand pounds and only 1 octane higher you were having timing pulled. You can monitor knock sensors with the tuner (at least I can with my flashpaq) so you could see to be sure. If I put anything over 2,000 lb in my bed or a trailer I set to the 87 perf tune and run either 91 or 93 octane. You may have been ok there though, you'd have to look at the timing to see.
 

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Discussion Starter · #7 ·
Ok, I'd still bet that with a few thousand pounds and only 1 octane higher you were having timing pulled. You can monitor knock sensors with the tuner (at least I can with my flashpaq) so you could see to be sure. If I put anything over 2,000 lb in my bed or a trailer I set to the 87 perf tune and run either 91 or 93 octane. You may have been ok there though, you'd have to look at the timing to see.
I doubt it. Ive done my fair share of playing with octane when I used to race, mixing fuel, determining what octane needed to prevent ping under full load etc. I can datalog with my diablosport, but it'll be a waste of time because im not worried about it. I listen to the engine out of habit, it comes natural and I do it without thinking about it. Running 93 on an 87 tune is overkill IMO, not my truck and it's only a few $ more(so no harm) but not needed.
 

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Discussion Starter · #8 ·
But I do appreciate your concern, it's good info for people that are not familiar with octane requirements, towing and how a load affects that. :smileup:
 
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