MOBILE HEALTH CLINICS
Vehicle Fuel Considerations
Debate: Should we go with gas or diesel?
MHCA offers the following comments and resources
Hermann Spetzler, CEO
OPEN DOOR Community Health Centers
"We have decided to use gas only in our rural area. Mainly the issue is the smell which is often a problem in the enclosed vehicle when using diesel if the generators are not diesel than that changes the decision making process. "
Jennifer Bennet, Executive Director
The Family Van, Harvard Medical School
"Alternative fuel options were an important consideration when deciding to purchase our new van. New England and particularly the low-income communities we serve here in Boston are disproportionately afflicted with Asthma. Emissions are roughly cut in half with the use of bio-diesel and the increased lubricity will also result in less wear and tear for our engine. With all of these benefits in mind we purchased a diesel van."
Kathy Ficco, Executive Director
St. Joseph Community Health Clinics
Santa Rosa, CA
"It's my understanding that in California there is an effort underway to convert all diesel school buses from diesel to gas to reduce the incidence and impact of asthma for children in urban areas. Since our mobile clinics frequently serve children at school sites and since we promote health and wellness, when we purchased our new unit in 2002 we went with a gas powered mobile unit. "
Brenda Merritt, MD, Clinical Director
New York City
"We changed from gas to diesel, when we changed from an RV to a truck and chassis. The community does complain about the fumes and it is louder. But for our next vehicle we are staying with diesel."
The Motor Trend website offers a pros and cons discussion. Although it's not directly related to Mobile Health vehicles, the general information is worth your consideration.
Gas has better acceleration, but diesel has better torque so better for heavy trucks, vans.
Gas gives more pollution, but doesn't smell as bad.
Diesel has better engine life.
Diesel has better mileage and is less expensive.
An interesting website to consider is Grinning Planet - Saving the Planet One Joke At A Time.
Gas produces very small (size) particulate matter that remains suspended in the atmosphere and results in long lasting smog.
Diesel's large particulates fall out to ground quicker. Also, the large size particulates are caught in the mucus and hair of respiratory systems and are not as readily absorbed in the blood system.
Here's an example of when a diesel engine may be preferable ... a 40' vehicle (with two operatories or exam rooms) customized for dental care or mammography may be exceptionally heavy due to the weight of the equipment. A diesel engine has the ability to properly handle the requirements of a heavy vehicle. Note - a vehicle this size will likely require a CDL (commercial drivers license).
Following are some benefits to going diesel (vs gas):
- Greater durability - diesel engines have lower piston speeds, a larger bearing area, better internal oil and piston cooling and a larger crankshaft
- Engine life - diesel engines are proven to last at least three times longer
- Greater torque - diesel engines provide reliable acceleration and hill-climbing ability
- More useable horsepower - diesel engines develop maximum horsepower within typical RPM operating range while gasoline engines only achieve maximum horsepower at extremely high RPM
- Safer operation - diesel fuel has a lower flash point
- Better burn rate - diesel engines have a lower hydrocarbon (unburned fuel) rate
- Less maintenance - diesel engines require up to five times fewer oil changes and have 50% fewer parts to maintain and replace
- Fuel economy - it is estimated that diesel engines deliver 40% better fuel economy
- Residual value - vehicles with diesel engines often command higher resale value
- To minimize gas or diesel fuel odor within the vehicle, divert emissions above the vehicle, not from below.
- Diesel engines can run on bio-diesel fuel made from soybeans ... very clean.
American Lung Association of Metropolitan Chicago
Brian Urbaszewski, Director of Environmental Health Programs
This summer refineries across the US started to produce "ultra low sulfur diesel" fuel. They are mandated by the US EPA to do so. This new diesel fuel has about 98% less sulfur in it than the diesel fuel produced just a few months ago. It will take a while to flush the whole distribution system (pipelines, tanker trucks, underground tanks, etc) but the end result is that every pump that services vehicles has to meet this standard by mid- October. While this sounds super clean, it's really only half of the story. The clean fuel will reduce actual tailpipe emissions by about 10 percent, more or less, for existing vehicles. Great, but not stellar. The real benefits come from the addition of Diesel Particulate Filters (aka soot traps, particulate traps, filters, etc.) COMBINED with the clean diesel, you will cut tailpipe emissions by about 90 percent.
Doing the math, you can see most of the benefit is in that trap device. It is required on every new model year 2007 and subsequent model year vehicles. So the new 2007 model year diesel RVs that get turned into mobile clinics will have these devices on them when they come fresh from the factory, and will be about 90 percent cleaner than a 2006 model year RV clinic. Basically the "trap" devices simply won't work right with the dirtier, high sulfur fuel. Its analogous to cars; you have to use unleaded fuel otherwise you will completely ruin and render ineffective the catalytic converter under the car that actually breaks down most air pollution before it leaves your tailpipe.
Now I believe you CAN retrofit an older RV with these devices with a "trap", but it will cost several thousand dollars (ballpark $6,000-7000). This has been done with school buses, construction equipment and transit buses. Beware that there are cheaper diesel soot reduction devices called oxidation catalysts (aka "oxycats", catalysts, etc) that are nowhere near as effective. They generally reduce about 20-50% of tailpipe pollution, depending on what pollutant you look at and how expensive the device is. You do generally get what you pay for. Particulate filters physically trap the diesel soot and incinerate it; they are permeable and only exhaust out gases. Oxycats have a structure that looks like holding up a handful of about 100 soda straws in your hands and looking through them. The exhaust travels through the straws and some of it breaks down as exhaust particles bounce through, but a lot of pollution also makes it to the other side and then out the tailpipe.
So, the one point is IF you buy a diesel RV, don't buy anything older than a 2007 model year vehicle, because it will be many times dirtier. If you have a diesel RV (pre-2007 vintage) it really, really needs a diesel particulate filter/trap - NOT an oxidation catalyst. An oxidation calalyst will help a little bit, but it's not the best solution. Long story ... I don't have enough info to compare a 2007 gasoline RV to a 2007 diesel RV. I suspect Diesel will still be dirtier (they always are, and diesel engine pollution regulations are still more lax than those for gasoline engines), but don't have any hard numbers to back that up.
We do have a basic fact sheet on retrofitting older vehicles -
Much more extensive treatment at:
Gas vs diesel ... clearly, this is a long debate. If you have additional comments to add, experiences to share, or resources to suggest, please email MHCA ... firstname.lastname@example.org
If your organization is planning to purchase a custom Mobile Health (medical or dental) vehicle, MHCA is available to offer the following assistance:
- general advice and information
- identify vehicle specifications
- secure cost estimates submit RFPs to specialty vehicle manufacturers