I know this has been beat to death but I want to talk to the guys that have helped me in the past before I do something drastic! Last October I traded in my 2002 F-250 CC SB 4X4 6.8 with 92k on it for a 2003 F-350 CC LB 4X4 Lariat with 20k on it. I have noticed a few things about this new rig Im not shure are normal so hear we go....

Last Sat. I got a new camper and towed it home. The trip was about 150 miles and I got 6.1 mpg The 2002 I got around 9mpg.

This new rig wanders. I am used to driving big trucks and I have a 76 high boy that drives better. It like hurding kittens down the road. I do have 285s rather than the factory 265s but I cant think that would cause that much dif.

All and all I like my truck but the performance and mpg seem to have taken a dive when I moved from the 02 to the 03??? I just dont get it

My new camper comes in at around 7000lb and I read guys pulling 15k and getting better mpg. Whats the deal?

I hope some one can shed some light on this for me... Im thinking of doing the unthinkable but I dont see many options...


Please help
JT

 

Is there a difference in gearing, Jason?

 

Im sorry! No they are both 3:73s

 

Sounds to me like you did NOT have a load leveling hitch or if you did then the bias was set up incorrectly. If you have too much down force on the front axle or to little down force the damned thing will wander all over the road... especially on side winds.

Set up the truck and trailer on very flat area. Make sure your tire pressures are correct for the loaded truck and added trailer weight. (These beasts are real sensitive to unbalanced tire pressures also)

Do the set up of the load distributing hitch exactly as laid out on the hitches owners guide. If a 5th wheel the same condition can happen if the pin weight is not centered within the recommended distance of the rear axle. And again if the pin weight is too high OR too low then the front wander problem is back.

I been doing this so many years now on so many different trucks and different trailers, that I never trust my memory, I keep the guides and manuals.

But trust me if the load distribution ain't right you get the herding cats syndrome every time and it can get real dangerous.

I shudder every time I pass a pickup truck hauling a goosneck and large backhoe with the front end pointing to the moon!

 

Thank you Fred! That may verry well be the problem. I have set up many truck, trailer combos and I did set this one up myself on level ground but I could have got it off! I seem to find the wandering with no load at all also. I read a post a year or so back about these trucks wandering and I thought to my self these guys just dont know what to expect from a larger truck. I never have had any problems with wandering with the 2002 or any other truck Ive had for that matter.. But I will check out my hitch and make shure it is set up correctly and level...

Do you have any comments on 6.1mpg? Im not trying to be a whiner I did not buy a V-10 expecting to get 25mpg nor am I dissatisfied with the power if that was the case I would not have bought a second one! Im just shocked at the dif between the two trucks.

Thanks
JT

 

You may need more pin weight. Since it's a new trailer I will assume it's empty. Add all your stuff, water and food you may find it's better.

I also suggest you check to make sure the trailer is level and you don't have too much or too little pressure in the load bars. This of course assumes you have a load leveling hitch. Another thing, do you have sway control and is it adjusted correctly?

I get around 7mpg towing 7700 lb 5th wheel. I have gotten as little as 6 when going over mountains. Winter blend fuel may also have an impact on the numbers you are getting.

 

The larger tires my also skew the mpg numbers. If the speedo hasn't been reset then you're logging less miles than traveling. Example: If the speedo says 65, you're probably doing close to 70. So in an hour, you've traveled 70 miles but the odo says 65. When you do the math you're off by 5 miles. The larger tires will aslo make the truck downshift more and you'll use more gas because you'e running a higher rpm. Are the 285's on stock wheels? The stock wheels will work but they are too narrow for the 285's. That could cause some wonder too.

 

According to this site www.net-comber.com/tirecalc.html using 75 series tires for both tread widths the vehicle will be going 67.43 mph when you are going 65. That's a 4% difference.

I don't have the math to figure out the impact on MPG. (duh)

 

http://www.4lo.com/calc/geartire.htm

Go to this site and it will tell you all you want to know about tire size conversions!

That is a good point!

According to that site I am going 69.9mph when the speedo says 65.

Can that make that much dif in mpg readings? I meen respectivly I figured I went 150 miles at 72(speedo) and the mpg was 6.1... can someone with better math than I figure that out?

JT

 

No help with the math Jasontrucks76 but in my long winded earlier post I forgot to mention the 285s as part of the wander and MPG problem. Up hill, head wind, wrong tire size, wrong tire pressures, and un balanced load can put the mpgs in the toilet. You are probably rally going to see 7.5 to 8.4mpg once you get her set up right. I HIGHLY recommend getting back to the 265 series for her as I suspect you have 3.73:1 rear gears and the 310HP 2v V10.... that motor needs to be about 1950-2150 at 65-70 mph for best cruise and mph. Do not be afraid to drop out of OD and run that motor well up into the 4000+ range to climb hills. My towing MPG averages were always in the high 6s to mid 8mpg at freeway speeds. I could back her to 55-65mph and get high 8 to low 9mpg but that was no fun (grin)

 

Ok, this could be really wrong but this is what I figured. 150 miles divided by 6.1mpg equals 24.59 gallons of gas. The difference between 65 and 69.9 is about 7.4%. 150 miles plus 7.4% is 161.1 miles. 161.1 miles divided by 24.59 gallons of gas equals 6.55 mpg. Don't you feel better now??

 

With a 2003...you might still have the factory warranty right? If you do...then RUN do not walk to the dealer. Have them check the ball joints for excessive play.

Tire size is a problem. My 2003 F250 4x4 when I purchased it "used" had 285s on it and my SD wondered all over the place. I replaced with stock 265s and the wonder is gone.

Not only do the larger tires use more fuel, but when towing...you are actually reducing the 3.73s...which are not good gears for towing anyway.

Good luck,
biz

 

Well as always guys you have given me some good food for thought I am shure that my load leveling hitch is set up correctly now. I hooked back up and everything looks good!

I have given the tire size quite a bit of thought and I know when its time I will put 265s back on this truck for shure. The 285s look good but are not worth loosing power or mpg.

Thanks for the math class V-10man. I figured it wouldnt make that much diff but every little bit helps and if Biz4two you have had the exact same thing happen than I would guess that must be the wondering problem with mine also!

Fred as to the rpms I was unable to tow in OD on this trip. Even if I ran with OD on it would only kick into OD when going down hill. So I left it off. If I remember correctly I was running 72(speedo) and rpms were about 28k. I am not scared to kick her down and let her rip. I love the sound of 4000+rpms The first time I heard it it put me into panic mode but being my second V-10 now I get it (BSEG)

So as far as 6ish mpg it looks like thats the way it is? If you guys are seeing the same Ill deal with it. I can buy a lot of gas for the $20grand to trade in on a new truck

As always thanks FTE
And thanks for the input
JT

 

truth my V10 brother, especially with the 3.73 ring and pinion. The difference is amazing, I dropped from a 265 to a 225, the 285 tires gives an 'effective' gear ratio of 3.47 to 1. I got an 'effective' gear ratio of 3.88 to 1. The engine is much more in it's sweet spot when towing. I also got 15.6 mpg on a solo trip of close to 700 miles recently. This engine likes to run up in it's comfort zone.

And finally, as someone else pointed out, the 32.8" tires are reporting LESS miles than actually traveled so he'll need to factor that back in to his mileage calculations.

Even a small change of 3.73 to an effective 3.88 made a big difference in driving, I'm seriously considering 4.10's but going to wait until I get the lowering kit put on as I may need to go with an even shorter sidewall which will help even more.