I have a question. I have an early 99 F350 SRW 6sp MT 2wd CC LB, and 3.73 rears. I only get about 10.5 mpg while towing. The travel trailer is 28' long, and weighs about 6500 - 7500# (I need to scale it). When I hear some claim 12-15 towing similar weights , 2 things come to my mind: Either I am calculating it wrong (Miles / Gallons = MPG), or I am driving it wrong. I can tow in OD at about 60 MPH (1700 RPM) and hold speed. EGT runs about 900 on the flats, and 1100 climbing hills. I get about 10.6 mpg. I can tow at 70 mph (2150 RPM) and it tows beautifully, EGT runs about 950 on flat, and 1150 climbing, and I get about 10.3 MPG. Truck is stock except for 6637 air cleaner, and a shim under fuel pressure regulator. The previous owner claimed 14 towing a 15000# 5th wheel. What am I doing wrong?????? Would I do better dropping a gear and running about 60 MPH (2000 RPM)?? Otherwise, economy is good without the trailer. I got 18.5 on winter fuel last time I took a trip, and ran 70 MPH on I80.
Two things come to mind.... 1. Some people like to add 1 or 2mpg's when they go to state what they are getting. Your PO may have fudged just a 'tad to help get the truck sold. 2. I believe this new ultra low sulfer fuel has hurt us some on economy. I think too, that it really hurts when you are working the engine fairly good and are consuming a fair amount, meaning I think that as more fuel under load is needed, the higher rate of inifficiency goes up. 2 years ago when I went West Yellowstone from California with a 2002 Dodge 6spd dually pulling a 7K 27' enclosed sled trailer, we got between 13-13.5mpg cruising 70mph and pulling hills 70-80mph. This was all before the new fuel Just this last winter with the same rig (nothing changed on the truck or trailer) headed to Diamond Lake, Oregon, 10-11mpg..... with ULSD fuel. I used to get 15mpg or so in town with my Dodge unloaded, now I struggle to get 14. I *used* to get 21-23mpg on the highway.... now I struggle for high 18's it seems.
Same thing here. I just came back from Florida and got around 10-11 mpg. Used to get around 12.5-13.5 towing the same weight 5er. I also think and read the ultra-low sulfur diesel has a big part in low mpg. I only get around 18mpg if I keep my foot out of it.
I do ok on mileage. I got about 10.5 pulling to and from Washington, but I know the 35" tires and 4 speed transmission had NOTHING to do with that! I think you are just a touch low. First, check your trailer and make sure you don't have a bearing too tight or maybe a brake dragging. Next, if the truck is bone stock then there is a good chance the muffler is clogged up with soot, and restricting exhaust flow. Exhaust temps look good, providing the probe is mounted preturbo. If its in the downpipe then that would tell us there is an issue there. Amsoil sells a new intake made by Donaldson that is pretty sweet. You can actually pick on up at the Ford dealer, but Amsoil sells it for much less. Try some fuel additive to clean out the injection system and help with some of the lubricity this new fuel tends to lack. Might help your mileage out a little. I have a customer with a 93 Dodge that says he gets 2 extra MPG using the Diesel Concentrate from Amsoil. I use the stuff every tank in both of my diesels.
A few years ago my father had the same truck. He got about 20-22 around town and on long trips hauling his 30ft travel trailer never got less than 18mpg. It had the hypertech programmer on it. I use to borrow it to pull my K5 and it got 20mpg. His went to crap when the #8 injector went bad, dropped it about 4-5 mpg. Instead of fixing it, he sold the truck. Wishes everyday since then he still had it. But it very well could be the fuel now days.
I get 13.5 mpg pulling my 91 30' travel trailer not sure what it weighs I think around 6500 lbs. I normally run 60 mph in sixth gear.
I have a 3:54:1 in my Dodge. I also have a 6sp manual tranny (NV5600) When I tow my fiver at 55-60 I always stay in 5th gear. That way I get the full advantage of the rear ratio at 1:1. I pull into OD above 60mph. I have an overhead MPG indicator that gives MPG as you drive right now and not the average. At 55MPH in 5th its showing 13.5-14 on flat ground. I use this device to select the best gear for the situation. In sixth gear at 65mph it's around 11. At 70mph its 10. Trailer weight is just under 14,000lbs. Its a stock 235hp 460 ft/lbs Cummins with an exhaust brake now with a 177k on the clock. I know that if I keep this truck and start using the Fiver alot, I will change the rear to 4:10. With a 4:10 this truck will get 12.5-13 mpg towing at 65mph. Cummins says if you are going to work the truck, you must be running 2200-2300 rpm at 65mph. I think you'll find the 7.3 is about the same. I know guys with them that pull loads similar to mine with the 4:10 with good results. Look at the 450 and 550 with 4:88's and 5:13's. RPMs are up all the time, load is off the engine, EGT's are down and they have plenty of head start when they get to a hill. Not the best for fuel mileage running light. I can't imagine how a 650ft/lb torque cummins would act with a 4:10 in a 3500. Dave
I think the ULSD has the biggest effect on fuel mileage. My truck does not seem to be taking a huge hit, but enough to notice a little (1MPG Maybe).. Don't know, everything else still seems to work well, pulls great and unloaded mileage is still over 20MPG (35K miles)... Scotty
14 mpg tugging a 15,000 pound 5er???? Give me a break!:doah: Just got back from another trip out to the Rockies. Was pulling the 14RT at 4000 lbs. Had a cap on the back of the truck for the dogs to ride in. It's about 8 inches taller than the roof of the camper, but don't know if any air is streaming over the trailer or if it makes up for the extra drag of the cap itself. I averaged 18.7 mpg (at 65mph) till I reached the Mississippi in Missouri. That dropped to 17.0 even by the time we reached Colorado Springs, CO. Slowed down to around 50-55 through Colorado, into Utah and up through Wyoming. Took I-90 East to I-35 South (to avoid Chicago) to I-80 the rest of the way home. Again with the cruise set at 65 and in 6th gear, we averaged 18.2 on the way home (hand calculated). We've made the same trip pulling our 8000 lb 5er and averaged 12.7 for the whole trip using the stock tires on the truck. Try using different brands of fuels. My truck is really picky on what I put in the tank. It can mean 3-4 mpg difference from what it likes and what it doesn't. I also use PowerService additive. It has made a 2 mpg difference in the ULSD. Also, don't be afraid to slow down a little. My Cummins is happiest around 1800 RPM's. Problem is, because of my gearing, that leaves me at just over 52 mph. I'm at almost 2100 rpm at 65 mph, but I lost a few MPG. Once I go over 65, my fuel economy goes down quick. It doesn't sound like you're too far off from where you should be. A performance intake and exhaust can help fuel mileage and add some power in the process, whether you are towing or not. Below are the RV's we've pulled out West.
Have you gotten the PCM flash for your 2005? There's a TSB out for "poor" fuel ecomony for the 2004.5-2005 Cummins trucks. Also, I see in your sig you mention something about Banks. Is it the High Ram intake elbow? I've read several posts on some Dodge truck sites of people losing MPG when they switched out their stock elbow for the Banks unit. Just wondered.
I do have the Banks High Ram, but the mpg was low before this bolt-on. None of the "bolt-ons" changed the fuel milage, it has been the same poor mpg as new. With 40k miles on the odometer you would think it would increase some. But I don't expect tow vehicles to get great mpg. I'll look into the PCM flash, thanks.
