Air Flow Deflectors

CavemanCharlie wrote:

BackOfThePack wrote:
The days trip plan trumps aero aids (any spending to save). It’s basic as to all stops planned, travel speed below the crowd on cruise control, and maximum vehicle separation while traveling. Zero idling.

“Trip plan” is a term used by truck drivers to account for all the days details — the how to — to maximize hours available at the best rate of speed (where speed is governed).

With RVs otherwise identical, your aero aids and my better trip plan will cause me to “win” the MPG game on a daily basis.

Once one understands how little time over the course of a full day one actually spends at cruise speed, the pieces fall into place.

I’m hardly against an aero rig, I spec’d both TV & TT for longest life with highest reliability at lowest cost of operation. Aero (plus a high compression engined TV) is central. But it has to be built-in at vehicle specification to be truly effective.

Average Speed (Engine Hours vs Odometer Miles) is related to Average MPG, directly. The aero wall is at 60-mph. No one gets better MPG above this. The rate of increase rises so rapidly above 65-mph that most big trucks are governed at 65-67/mph. “Time saved” no longer works past this (traffic volume and driver stress).

The RV lane in all this (Interstste) is from 62-64/mph. Not faster. No lane changes. No accel/decel events of any note. CONTROL of pre-planned stops and off-road minutes (driving, too) is major changes in AVERAGE mph & mpg. Which is the game.

I drove Chicago to Fort Worth in a rental identical to my sons car. He likes to run 70+. I eased along at 64-mph. His lower mpg meant he lost enough time for extra fuel that — on a trip just over 1,000-miles — his DRIVING time savings would have been 40-minutes (assuming he controlled time at pre-planned stops as well as I do. He doesn’t). He’d have burned 2/3 an extra tank of fuel to have done the same work. And likely arrived no earlier (is the point). As a transport-rated ex-military pilot he certainly understands all this.

So, you retired guys and budget-pinching Rvers pay attention: chasing pennies at a remote fuel stop WILL COST MORE. Risk, time and stress.

Save money during your commuter daily miles and it underwrites travel. Ten years ago when fuel was $4 and higher I figured out how to save enough annually in my daily driving to pay for 5,000-miles of “free” vacation fuel. You can too. Keep records of all gallons used and watch out for Average MPH. If yours is below 27-MPH as an average you’re a poor driver and abusive operator.

Apply a common sense attitude BEFORE you try spending money to save money.
Keep records and apply some discipline in ALL driving.

I think I understand and agree with most of your post. I don't understand the part you said " If yours is below 27-MPH as an average you’re a poor driver and abusive operator." That has me confused.

Most of what you are saying is to just plan you trip in advance, get on the highway, set the cruse control, and avoid starts /stops / idling etc. That all makes sense.


But, don't travel to much below the crowd speed. You are a hazard to traffic when everyone has to change lanes to go around you.

There are limits to this of course. If everyone is going 80 I'm not suggesting you should go 80! But, 65-70 is good towing speed on the interstate. If you want to go slower then that find a nice back road. One that is listed for 55-60 and enjoy the scenery. That is fun too and I often do that.

Average MPH = All Miles divided by Engine Hours.

The legal Interstate speed is a RANGE and usually from 45-70/mph. Traveling 60-62/mph is hardly a problem. One watches mirrors and dies his best to get traffic around.

The “danger” comes from those with ZERO regard for others. “Too fast for conditions” isn’t about weather, first, it’s about TRAFFIC VOLUME. Thoroughly illegal to use the left lane as a travel lane as a higher speed IS NOT a defense for screwing things up for others.

How many here understand that it is illegal to block entry to the passing lane?
YOU will be at fault, or overturned in the median, for such disregard.

Multiple vehicles in the left lane is a recent phenomenon (didn’t exist before late 1990s), AND DO NOT HAVE R.O.W. in any situation. “Passing” is one at a time.

Only the right lane is for travell, and ONLY the travel lane has Right-Of-Way. (Make your pass SHORT in duration; get on the throttle).

I’m coming up on someone slow my left turn signal comes on when I see a gap. That’s a sign to other drivers illegally in the passing lane. I’m not asking permission.

If one wants Fuel Economy, then that’s with (ideally) ZERO lane changes, ZERO braking or acceleration events (use terrain). If I can run 700-miles without passing anyone outside the city in a big truck at 62-mph, then can anyone. It’s not impossible to find those below 60, but they’re rare once away from metros. (Thry catch you by surprise, then you ain’t doing your job).

A combination RV is pretty much the worst handling/braking vehicle on the highway. “Stupid” is the guy in the left lane COMPLETELY surrounded with no way out of his dunderhead driving. (Tell us about your “skill”, we might need the laugh).

The game is to maintain the very greatest distance between self and others all day long. It’s not hard, it just needs new habits. Great rear view mirrors.

Safety & Fuel Economy track each other. The former always pre-empty the latter when it comes up.

Steady & Smooth. Year around. Solo or towing.

An air deflector may or may not show a difference. But until one has comprehensive records (cents-per-mile), “proving it” is quite another thing.

Average MPH below 27 is abuse. It’s not hard (again) to have better regard for the engine. Some new habits. The difference is right there on the annual fuel expenditure line. And even more so on the vehicle longevity calculation.

Engines have a maximum life in terms of gallons used as one way of tracking life. Miles aren’t as important.

“Spend to Save” world best in initial vehicle specification. Much harder later to recoup costs with magic gadgets. Those that work ONLY at aero-difficult speeds are LEAST likely to pay for themselves as time spent at steady-state cruise is so low.

Do the numbers. See for yourself.

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