Just took a 1780 mile trip with our 25' TT and my milage dropped 1 mpg from a trip a year ago, I did add a camper shell. Does anyone think this would cause a loss in mpg? I have 33k and only had 18k a year ago when my mpg was 12.5 avg and 11.6 this trip. The trip last year was up to Yellowstone and on into Montana, Idaho and back with a lot of moutains and this last trip was only in Louisiana, Arkansas, Oklahoma and Texas. Any ideas on the use of the camper shell or on anything else.
wesran

 

A few years ago I read an article discussing truck design with regards to aerodynamics.

In a nutshell it stated that truck cabs are designed to divert air flow slightly up and way from the bed via the resulting air bubble (this is why items behind the cab don't get wet when raining. Not just because you are going fast ).

This bubble effect lessens air drag on the tail gates. Thru testing they showed that any modification to the bed...lowered tail gates, bed mount tool boxes, tonnuea covers, camper shells, loads, etc....restricted the air bubble and actually created drag, thereby, affecting MPG.

Food for thought anyway.

 

I would guess more than likely fuel quality and grade of the road. You are still average IMO.

 

With the switchover to ULSD I have read I believe on the Chevron site that There is an expected 1% loss of MPG with the new fuel. Wonder if you got some on the trip.

 

Perhaps the topography/terrain played a role? I have experienced excellent roadtrip mpg while in mountainous terrain...It could be the 6.0 mileage isn't as adversely affected (especially compared to a gasser) when working hard while traveling up the mountain and still enjoys the great mpg benefit of going down Thus, many times the mountains really don't have an overall negative mpg effect

Another issue is humidity- Or the lack thereof. The Montana/Idaho trip was low humidity and (I'm guessing) the other trip was quite humid. The best roadtrip mpg I ever get is in Southern Utah (high desert/extremely low humidity) with very hot temps. Anything is possible

 

The Chevron article states that it sustains a 1% energy loss. The translation to 5 of MPG loss would likely be somewhat different. I have read anywhere from 3 - 5 %. I would bet that info is even under control conditions. Whether they be lab tests of field test. It will be interesting to see what happens in the real world.

The Chevron site also states that there is a cetane drop as well. IMO, this has the opportunity to create hard start issues.

So, we may be faced with higher prices, lower MPG and for those not using centane boosters...hard starts.

 

When I added the shell to my truck, I actually noticed better fuel economy. Not by much, only about 0.5 to 0.6, but an improvement none the less. Of course, mine is still very low mileage and not broke in so that improvement could have been due to getting more broke in too.

 

KW check out this UK BP site on the cetane level. wish we could all have this fuel.http://www.bp.com/sectiongenericarti...tentId=7009145

 

Yes, it would be nice. But, the problem with their story is, the benefit from higher cetane values tend to plateau after a value of 50 is obtained.

They are putting a lot of spin on 55+ cetane.

Wesran, did you use fuel additives on both trips?

 

I was reading something about cetane ratings and recall that anything above 50 did not produce much difference.

 

Yes I had just started using stanadyne on the first trip and have since changed to Power Serve and I do use it at every fill up.
Let me say that I did not add the camper shell to improve my milage but to protect my dogs. It will not be a permanent fixture as I like to use my truck for what it was built for. There seems to be so many varibles in this MPG debate that I hesitate to even get into it but there has to be some common ground some where. All of the inputs above seem to point to these different varibles and I certainly appreciate the input. The one thing I see that stands out is the cetane issue and as stated before on FTE very few fuel stops know what you are talking about if you ask and I think teaxas may be the only state that I traveled in that has a standard. And the other thing is we want to conserve energy but we have a govt agency go the other way. Thanks again for the input and keep it coming.
wesran

 

Last summmer I did an 8000 trip from Philadelphia area to Montana, Idaho, Utah and back pulling a 26 foot travel trailer. I keep good records and averaged 11.9 mpg, almost exactly what you did. I had a camper shell on my 8'bed and a front bike rack on the truck. I used Stantedyne in every fillup.

 

I had another link showing that down the pipeline it is 40 cetane. Terminals and stations change it from there with additive packages.