Fuel mileage when towing... {crazy} !
 

Okay now, I don't even have any actual mpg numbers yet, but I just had a really interesting revelation yesterday, during the first towing of my boat.....

Now for starters, let me ask your opinion on something;

How much do the RPM's of your motor have to do with mileage ? Is this 100% of the equasion ? 75% ? 50% ? I mean, I know this makes a big difference, I just don't know how much.

Okay, so traveling down the highway at 65mph "without my boat", my truck is turning 1825 rpm's. {note; I do have larger than stock tires, but I've already done the calculations for this, so I'm talking, an "actual" 65 mph, or very close to it}.

So yesterday, I hook up my light little 14 ft aluminum, get out on the highway, and push the truck up to 'only' 60 mph. I look down at the tachometer, and I was shocked {in a good way :-) that it was only turning at 1550 rpms ! ....or nearly 300 rpm's slower, to pull my boat at 60 mph, as opposed to pulling just itself, at 65 mph !

Well, I can sure see why speed has SOOO much to do with mileage. But the $10K question is (and the whole reason for this post) since before I even got my truck, my biggest concern was not mpg in general, but rather, mpg when towing the boat, since 98% of my trucks miles will end up being towing miles.....
And basically everyone said > You will notice at least some small drop in mileage. Hmmmm... maybe they were not expecting my rpm's to drop from 1825 without the boat behind, to 1550 "with" ! Or maybe they were not accounting for the fact that my speed was going from 65 mph to 60 mph.

But anyway, with these facts in mind, is it concievable that I will actually end up getting considerably "better" mileage towing my boat at 60 mph / 1550 rpm's, than driving the truck alone, at 65 mph / 1825 rpm's ?

Kind of crazy, huh ?

Your thoughts please,
Fish

PS, The only thing I have not checked, is my rpm's, at 60 mph "without" the boat. I really just can't imagine its going to turn any noticeable amount slower that 1550. In other words, I think my little light boat might be having a very small negative effect, while slowing from 65 mph, to 60 mph is having a substantial positive effect ! Which {for a definite change in attitude, when discussing fuel mileage} would just be ALL good :-)

PPS, Towing my boat at 'only' 60 mph, I'm still breaking the CA towing speed limit by 5 mph.... just trying to keep from being run over, by a 70 mph big rig !

Chris,

I can tell you from experience that driving 65-70 MPH gets me about 15 MPG, as opposed to driving 50-55 MPH which gets over 20 MPG. On road trips, with flat roadways and no wind, I've seen upwards of 25-26 MPG with speeds of 50-55 MPH.

5150

Your rpm's will be probably close to the same but I don't think you will see an improvement in your mpg's because your truck will be pulling more weight. The rpm's are only half the the story the rest comes from the weight of everything. More weight= More work= More fuel consumption to compensate for extra work needing to be done.

Hey guys....
 

5150, you know there would be a lot of guys who would see you mention > "25 to 26 mpg in an F150" and think you were... well... 5150 ;-) But then I doubt you would find many guys who would drive their F150's at 50 to 55 mph, even when towing something.
Let me put it this way if I could get 20 mpg towing my light aluminum at 60 mph / 1550 rpms, I'd be thrilled.

Okay 05, so your focusing on my "side comparison" {which I have not actually done yet} of the truck at 60 mph with, and 60 mph without, the boat. I agree that their would have to be some decrease in mileage, even if it were only miner. More weight, more work, more gas.
But again, I'm just hoping that driving slower, will make a much larger difference to the positive, which makes up for my decrease 2 or 3 X's over. And judging by the substantial decrease in rpm's, during my initial towing test run, it seems to show this.

I'll start compiling some actual mpg figures soon.

But then, I wonder how many miles my truck needs to be ran for a full break in (loosening up) of the motor, and what kind of mpg difference that will make ???

Hmmm,
Fish

I think the last two posts pretty much nailed it Fish. Your trailer is so light, your transmission is running the same way it does when you're not towing at similar speeds. By that, I mean the OD is probably engaged and your torque converter is locked.

But, the boat DOES add weight and some wind resistance. The RPMs are the same because the engine is using more fuel and air to perform the same amount of effort. I expect you would see a lower mpg figure running "clean" at 60 than you will get towing at 60. But, on level ground, I doubt the rpms will be different.

I can get similar rpm results pulling my 3600# trailer on level ground, but the gas mileage is worse than it would be if I were not towing.

- Jack

5k miles for full PCM torque unlock. people say it isnt there, but trust me it is ;)

Compare towing vs not at same speeds to really see how your mileage is affected. dont forget to adjust your mileage for you tire size. mine is off by almost 6% so i multiply by .9407

Thanks guy....
 

BTW, I don't know how I ended up posting this in the 97-03 section.... Mines an 08'.

But anyway yes, I think it would be a physical imposibility for my truck to get better mileage towing my light boat (or anything for that matter) than when it's not towing anything, but I'm driving it "at the same speed". However, I'm still hoping that driving slower when towing, will give me a bigger fuel savings, than driver faster, when I'm not towing.

I'm sure by now, everyone agrees that speed always hurts your mileage.....

Peace,
Fish

This is supposed to be the "Engine" forum, Fish - at least it was a couple of days ago. I think the "improvements" they've done on it have made it a bit schizophrenic. :lol:

- Jack

Thank you Jack.....
 

I thought I was just losing my freaking mind :-) ....course I still might be, but about stuff "other than" posting in the wrong forums :-) LOL

Peace,
Fish