Quote:
Originally Posted by Tugboat
Ok got 10.9 mpg today going 328 miles in 6 hours and 48 minutes. Will post exactly how much fuel I put in tomorrow when I top off and add it to what I put in on the way up
|
(Extra long post)
Another piece of the MPG puzzle is average mph. Not travel speed, but time from one point to another not including stops.
In this example it's 48-mph. For sake of argument let's assume there was no extended idle time. It was simply a route that featured slow roads.
On a trip of around 300-miles there is no "time savings" running faster than 58-62/mph. This includes Interstate.
I had a run starting in Fort Worth that would end at our Atlanta yard. Two days on IH20. Though I didn't plan it this way, it wound up being right at 400-miles each day. My cruise control set speed is a GPS-corrected 68-mph.
My average speed both days was 56-mph. Traffic, construction and the rest.
The two days drives were within five miles and three minutes.
With an RV keeping it below 65-mph keeps one well away from truck traffic governed at 65, and today's idiot car drivers running 70+.
Aerodynamic resistance shots skyward at 60-mph. A solo empty pickup can't stop or maneuver worth beans above 65. And peripheral vision narrows substantially near 70.
Under 65 means fewer lane changes. Less wind effect. Rarely running up on other traffic and having to brake. Reduced tire heat and reduced chassis stresses. Far better braking performance.
And a travel speed that is closer to average mph will show substantially less wasted fuel in acceleration and deceleration events.
All are welcome to read white papers published by Cummins and Kenworth the last ten years on fuel economy. Some of what I've written is implied.
Fuel economy, longevity, reliability and safety are pretty much all on the same page. Those papers note that the difference between drivers doing the exact same work is as much as 30%.
Guess which rig will last longest. It is what is meant by "driving smart".
MPG is one of several ways of estimating vehicle wear. Tire and brake life are others. A high average mph (total engine hours divided into total odometer miles) is beneficial. But it's not the same as high travel speed.
Some would rather buy another $120k in vehicles every 5-6 years and try to call huge depreciation losses normal. Some other would rather the TV last 15-years and the RV indefinitely.
Average mph is a clue about what works.
Some roads are slow and exact a penalty in stop and go plus traffic. That can be offset by a better choice of travel speed on the Interstate another day.
Travel in metro areas, solo, is where a great deal of improvement can be made. Can genuinely offset towing expense. Can literally underwrite towing with right attitude, planning and some skill acquisition.
Vehicle life average mph under 27 is cause for change. 30-35 is ideal. At 35-mph these light or medium duty diesels are about a 10,000-hour life before overhaul. Under 27-mph won't come close to that.
As to "flowing with traffic" and other childish excuses, don't even try.
The OPs question of what is the normal range in MPG needs to take in mind driver motivation. It's very low among RVers. Thus what matters more in making MPG comparisons is first vehicle spec. Then climate. Third is terrain.
Given a longer TV life, a percentage improvement to ANNUAL MPG -- and attention to average mph -- is the winning combination to a reduced per night expense aboard the RV for fuel.
What is the vacation expense? Total cost of the RV including finance, depreciation, fuel and ground rental, etc. Higher cost of tow vehicle versus a better choice for solo (someone without IRS deductible business mile s in using a 1T pickup). Factored into the number of nights aboard per year.
Reduction in fuel cost pays best with longest life of both vehicles. And how to best get them down the road.
So the easier way to find out what is "normal " is to conduct ones own test. Head out solo to the Interstate and fill up about 30-miles from home. Run a round trip on cruise control at 60-mph for 100-miles back to that same pump. Fill to to first click off both times.
The percentage change from solo to towing is the answer. Not the absolute number. 40% penalty in 1966 with a Ford Country Squire or in 2016 with a Ford Flex pulling the same travel trailer is an accurate rule of thumb.
Run out of town on the next vacation the same way. Fill up after majority of warmup at 45-miles. Fill up again the same way another 100-miles down the road.
These are likely "best possible" numbers for both configurations. Now there is a baseline.
This is how to gauge what is normal.
Linear Mode
