Fuel economy at 65 mph vs 60 mph

A diesel is most efficient at it,s torque peak. With my Cummins that is 1600rpm, which translates (with my current tires and gearing) to 63 mph. My mileage is slightly lower at 60 or 66 mph if it is dead calm wind. Add all the variables, wind, traffic, grades, driving style..... and just appreciate having your home with you. DRIVE SAFE AND COMFORTABLE>

double post oops

All other things being equal from my very unscientific research (basically, playing around and resetting my DIC MPG calculator) I'd guess it's around .5 mpg.

55 seems to be the sweet for optimal mileage (no surprise that's what the max was set at for years to save fuel). Every MPH over that and you are going to lose economy. Some vehicles may seem to be at a better RPM range and "feel" better but it's still taking more fuel to move that load the faster you go.

We got 11.5 yesterday running 63 mph. "Perfect Conditions "

62 is the sweet spot on my truck. At 62 rpms under 2000. No gear searching. Cruise control holds it steady. MPG 8.8. At 65 rpms at 2200 mpg 8.4. Cruise control occasionally kicks it out of overdrive. At 70mph rpms 2400. Cruise control more frequently kicks it out of overdrive. MPG 7.9.

There are many variable factors to consider including driving habits as to what MPG's a vehicle or when towing will get. Being a retired automotive engineer for decades, I can express what should normally be expected and what at difference speeds of 65 mph VS 58-60 mph.

I average 1.3 MPG higher at 58-60 mph than at 65 mph with the 5th wheel. 1.6 MPG higher with the Lance TC on the back for the same speeds. Both with the Chevy Duramax crew cab long box 4X4 same truck. The Carriage Carrilite 5th wheel scaled weighs 12,840 lbs and our 11'4" Lance truck camper scale weighs 3872 lbs. Both loaded to travel but with only a little freshwater in the tank.

This has been the average over close to 200,000 miles towing/carrying as this is what the ordered new truck is only used for. Never a daily driver as we have other vehicles.

Coasting to drain off speed to come to a stop rather than climbing on the binders helps and so does avoiding fast accelerations from a stop. You paid for the fuel to get up to a given speed so why not then let your speed drain off naturally and also save extra brake and tire wear?

Aerodynamics also make a sizable difference in fuel economy as can/will gear ratios. Head winds usually balance out with tail winds effects over the years. Up hill extra fuel use is also tempered a lot by downhill low fuel use.

Slower speeds does save fuel use/higher MPGs as that's very well documented along with being saver in emergency situations/loss of control/tire failures/etc. You, the driver, is in control of the choices and makes the decisions!

starcraft69 wrote:
We don't really care about fuel mileage anymore. I look at it this way. We just spent 21 days and 2200 miles on the road having fun, Fuel + RV parks came out to $78.00 a day over the whole trip. Out west here you cant even stay in a decent hotel for $78.00 a night and you would still have fuel cost. When ever anyone says wow what mileage do you get pulling that fifth wheel. I just ask them can you do the same things I do cheaper than $78.00 bucks a day????? My thought is if I need to get a certain mileage 12mpg not 9mpg It is time to stop traveling and just stay home, like most the people that ask me wow what mpg do you get pulling that fifth wheel. I understand people have a budget and this way of thinking is not for all, But it cost to travel so you pay gas or you pay hotels.

You can stay in a lot of hotels for $100,000. $50,000 for nicer 5th wheel and $50,000 for decent truck.
$30,000 for a nice car and $70,000 left for hotels and food. Gotta buy food anyway so it's a wash IMO.
Hotel room at $120.00 a night = 583 nights. We only camp about 40-50 nights max a year. So that would get us 12.95 years @45nights a year.
30+mpg in the car adds up too.
Hardly anyone keeps their trailer for 13 years so the process starts again.
Factor in the up keep on the trailer, ins, etc and you still spend more RV'ing.
With that being said I've done the hotel thing a lot when we had our Goldwing. It got old. We would much rather be in a CG somewhere. But to say that RV'is cheaper IMO it's not when the up front costs are included along with maintenance as well. Then factor in storage fees if needed. $0-50.00 a month to store it over 10 years adds up to $5400. Just do see it as cheaper.

As for the 60-65 mpg debate. I just go whatever speed I want depending on where I'm going and what traffic allows or what the price of diesel is.

My truck seems to always yield about the same fuel economy around here, right around 11 mpg, as soon as I go stateside into Maine, NH, Mass, I always seem to get slightly better in the 11.8-12mpg range - no idea why other than maybe always dealing with more wind around here. Speed can be anywhere from 55 to 65.

Haven't a clue......my hand calculations aren't that 'tight'

MIKECBROWN wrote:
A diesel is most efficient at it,s torque peak. With my Cummins that is 1600rpm, which translates (with my current tires and gearing) to 63 mph. My mileage is slightly lower at 60 or 66 mph if it is dead calm wind. Add all the variables, wind, traffic, grades, driving style..... and just appreciate having your home with you. DRIVE SAFE AND COMFORTABLE>

This is the rationale I follow. It's all about the RPMs. I drive at my engine's torque peak.