I’ve owned my 2014 Winnebago View Profile now for over a year.  Its a 26 ft class C motorhome with a small diesel engine (3.0L V6 Turbo diesel).  I bought it new, have driven over 28,000 miles, and have been very pleased with it.  For me, Its got just the right amount of living space and and just the right size for driving around.

This has been my first vehicle with a diesel engine and prior to getting this RV, I had no experience with diesel engines.  I thought the only change would be going to be going to a different pump at the gas stations.  But I’ve found it’s a little more involved than that.

So, I thought I’d share some of what I’ve learned about diesels (more specifically my diesel) in the post.

Diesel Fuel has More Stored Energy that Gasoline

A gallon of diesel has about 13% more stored energy energy than a gallon of gasoline (based on BTU ratings).  Basically, you get a more powerful explosion in the engine cylinder with diesel than you do with gasoline.  A bigger explosion means more power.  That’s why most big trucks and the big RV’s have diesel engines.  And that’s why my 11,000 lb RV can get along with a small little 3.0L V6 engine vs the 4.8L V8 that was in my 9,600 lb class B.  My Winnebago with the 3.0L diesel has more than enough power for going up big hills, towing, and for passing.

Its also why diesel engines are more fuel efficient that many gas engines.  Because of the higher stored energy, you need less diesel fuel to accomplish the same amount of work (e.g. horsepower) as gasoline.

Diesel Fuel is More Expensive

I’m not sure of all the reasons why this is so.  The Federal tax on diesel is 6 cents higher than gasoline.  The introduction of ultra low sulfur diesel added costs to the refining and transportation process and accounts for about a 10 cent premium over gasoline.  And the final reason appears to be demand.  Demand for gas is falling and demand for diesel (which powers most commercial vehicles) is increasing.

If you own a diesel powered RV, you’re going to pay more for fuel, but depending on your RV size, you may save some money based on fuel efficiency.  My Winnebago View averages about 16.5 mpg.  A similar sized gas Class C would get around 10-12 mpg.  So, for me it works to my advantage.  Diesel fuel is currently about 20% more expensive that gasoline, but I’m using about 30-40% less fuel per mile.

Not all Diesel Fuel is the Same

With gasoline, regular unleaded gas is regular unleaded gas.  The octane ratings may vary slight from supplier to supplier, but you can pretty much count on regular gas at any pump working fine in most gas engines.   Some engines may have minimum octane requirements that require a premium gas grade.

With gasoline, there are higher octane grades.  In the US, most gas is labeled as E10 which means it has a 10% ethanol content.  There’s also E15 in some places.  And, gas will go bad if it sits for a few months but, for every day use in standard engines, most regular grade gas works fine.  Not so with diesel.

First, there’s #1 diesel and #2 diesel.  Most of the diesel in the US is #2 regular diesel, which is similar to home heating oil. Then there’s #1 diesel, which is a lighter thinner weight diesel (more like kerosene) used in cold climates.  Sometimes you will see places with pumps labeled #1 or #2.  Most diesel in North America and Europe is Ultra Low Sulfur Diesel (ULSD), but sometimes you’ll see a pump labeled for off-road or tractor diesel which is not ULSD.

Biodiesel

Then, there’s this thing call biodiesel, which is regular diesel that is mixed with vegetable oil or animal fat.  Biodiesel has less energy (about 10% less) than regular diesel and not all engines will run ok with it.  Biodiesel has designations.  B5 means 5% biodiesel (5% vegetable oil content). There’s B10 and B20 meaning 10% and 20% biodiesel).

Biodiesel is less expensive and you will see it at many truck stops or no name fuel stations.  Sometimes the pumps are labeled and sometimes they’re not.  States like Minnesota and Washington mandate that all diesel be at least B2 (2% biodiesel).  Minnesota also mandates B10 during the summer months and is going to B20 by 2018.

My engine can only handle up to B5.  If you own a diesel, you should know what your engine can handle and look at the pumps to see if they’re labeled with Biodiesel stickers.  I’ve seen that many truck stops, like Pilot, Flying J, and Love’s sell diesel with up to a B20 content.  Because of my engines requirements, I avoid fueling at these places.

Bad Fuel

Lastly, diesel fuel can get contaminated with water and certain microbes.  Most diesel engines have fuel filters to trap this stuff and keep it out of the engine, but fuel filters can also become contaminated.  Contaminated fuel or fuel filter can cause poor engine performance and /or an engine fault code to set off the Check Engine Light (CEL).

I know this because I’ve had it happen a few times.  Dirty fuel can affect the burn temperature, O2 content, and fuel pressure.  My last CEL episode was caused by filling up at a small no name fuel stop and later necessitated a stop at the MB dealer to clear the fault codes for high fuel rail pressure.

The tech who worked on my engine said that 80% of the time, high or low fuel rail pressure is caused by bad fuel or a dirty fuel filter.  He gave me some good advice which I’ll share. Always fill up at a high volume brand name fuel station near a highway.  Places like Sunoco, BP, Shell, and Exxon.  The high volume places go through a lot of diesel so it doesn’t sit in the ground for long and collect water.  Also, he said avoid using biodiesel in my engine.  I’ve followed his advice for the past 6 months and have had no CEL episodes.

DEF and All that Entails

Most all diesel engines built after 2010 require the exhaust to be treated to reduce nitrous oxide emissions.  This is done by having a separate system that spays a mixture of water and urea into the exhaust to reduce the nitrous oxide that gets emitted out the tail pipe.  The water urea mixture is called DEF (Diesel Exhaust Fluid) or also called Ad Blue.  Its a consumable that you have to remember to fill up every so often.

My RV can go about 3,500 on my small 3.2 gallon DEF tank, but I keep it topped off every 500 miles.  How much DEF you’ll use is based on driving conditions, weight, terrain, etc. In my RV, the exhaust treatment system is a complicated system of sensors, tank, spray nozzles, heater, pump, level sensors and a computer system to monitor it all.

If something doesn’t go right with exhaust system, I get a fault code and CEL light that may  inhibit the engine function.  Too much nitrous oxide comes out the tail pipe, I’ll get a CEL.  My DEF runs low, I’ll get a warning light.  A sensors voltage goes out of range, I’ll get a CEL.  It’s a whole other area for faults or maintenance that doesn’t exist in a gas engine. You can get DEF at most Walmarts or trucks stop,  I always carry a 2.5 gallon jug with me.

There’s Less Maintenance, But Maintenance Can Costs More

My engine can go 15,000 between oil changes and service intervals.  That’s a long time.  But the engine takes 13 quarts of a special oil that costs $8 a quart.  An oil change on my RV can cost about $130 if I do it myself.  Double that if I bring it to the dealer. The only other regular maintenance for the engine are filters that need changing at specific intervals. The key one being a fuel filter.  My engine has one, but some larger RV’s have 2 or 3.  It important to know your service schedule and not to avoid the regular maintenance.  On gas engines, the service interval is usually around 5,000 or 7,500 miles.  Gas engines use about 1/2 the oil and it cost 1/2 as much. An oil change might run $50-$60 but you do it more often with a gas engine.

There’s less Places that Can Work on My Engine

My Class B with a Chevy 4.8L gas engine could be serviced anywhere.  My Mercedes Benz can only be serviced at a MB dealer that services Sprinter vans.  These are few and far between.  Its because of the computer system.  The MB engine has its own proprietary codes and system for diagnostics.  Luckily, I live about 20 miles away from a MB Sprinter Dealer, but it can sometimes take up to 3 weeks to get an appointment.  Its key to know where the closest engine service is when you’re buy an RV.  Luckily, engines today are pretty reliable but there have been times where I needed to drive 150 miles out of my way to get a CEL diagnosed while on  a trip.  Just something to be aware of.

Gas Vs. Diesel?

That’s what I’ve learned so far.  One of the big questions for many when buying an motorhome is the gas versus diesel question.  The gas motorhomes tend to be less expensive a because they’re built on a standard medium or heavy duty truck chassis.  They also may be a little less fuel efficient.  If you don’t drive a lot and have a limited budget, a gas model may make sense.  If you want a bigger coach or drive a lot of miles, a diesel may make more sense for the fuel efficiency and power.

I’m glad I went with a diesel.  I drive a lot each year (over 25,000 miles) and I figure I’m saving about $1,800 per year in fuel.  Yes, I paid more for my RV than a comparable gas model, but I was after a rig that was a certain size, had a certain level of quality, and had a high resale value.   Time will tell if it was less expensive.

Let me know if you have some more interesting facts or lessons you’ve learned about diesel engines.

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