It always amazes me the difference of 400, 500 lbs. can make with my 270. Most dramatic effects are felt on two lane, mountainous, tight turn roadways. Half tank of freshwater makes the difference, feels much more nimble and light along with better power makes for better handling characteristics. Although I always have a sense of security leaving home with full fresh water and fuel tanks, times when destination is unknown.
Doug,
Do you notice much of a difference in mileage?
Mileage seems to be determined more by the weight of my foot. Under the road conditions that I described I'm not one to have a line of cars behind me...I'm okay with following a slower vehicle I just don't want to be that guy.
Weight is a significant factor in MPG on mountains.
Virtually insignificant on flat ground.
Said another way, the HP demand on a grade is very dependent on weight.
HP demand on flat ground is very dependent on aerodynamic drag, with weight being a lot less of a factor.
Examples (from a Caterpillar Corp document, but applies to all heavy vehicles-- physics is physics). All HP requirements are HP at the rear wheels:
Flat ground, 55 MPH:
34,000 GCW coach103 HP
40,000 GCW coach 110 HP (only 7 HP more than lighter coach)
On 6% grade 55 MPH:
34,000 GCW coach 402 HP
40,000 GCW coach 462 HP (60 more HP than lighter coach)
Living in the mountains does use more fuel for us but those 6% grades are partially made up going down the other side. Speed and the associated drag is the biggest factor in a long distance trip. Lack of a tall high gear is also a factor for those of us with just a four speed transmission.
Pierce
Interesting topic since I will be heading out tomorrow with an empty coach. Never done that before with only me and a few items and 1000 miles to go to consignment. Will report in on how the coach handles.
Well the coach is officially on consignment at MOT.
After a 1000 mile road trip my experience with an unloaded coach (me, a cooler, a couple of changes of clothes and a sewer hose) was uneventful. I had empty black/grey tanks and about 1/4 tank of fresh water. Seriously, I may not be the most observant guy, but after unloading all the half timer stuff we carried, our coach performed like it normally does. I would have thought that the big piles of stuff removed from the coach would have made a difference, but not really.
I suppose 350HP and 1000 ft/lbs torque really does not care about an additional 4-5K of rolling weight?