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Mark My Words: Gas vs. diesel

Q. I’m currently contemplating the purchase of a fifth wheel. The unit I’m interested in is 14,000 pounds, so I’ll have to buy a bigger pickup to pull it. Do I want a diesel or a gas pickup? Why do I want either one? What advantages would one have over the other? Is there one you would recommend?  – Richard

A. First, be careful that you choose a truck that can adequately tow the loaded trailer and not exceed any of its weight ratings. It is hard to have too much truck and all too easy to have too little. Err on the side of excess capacity!

As to the selection of gas or diesel, I can only offer my opinion, which is sure to get me a lot of e-mails.

In the “old days,” diesel engines offered better fuel economy, longer-lasting engines, more torque, and diesel fuel was cheaper than gas. Today, with the advances in gasoline-engine technology, the increase in diesel emissions regulations and the fact that diesel fuel is now more expensive than gas, the playing field has leveled a lot.

For a trailer in your weight range, there are a lot of gas-engine tow vehicles that would be very acceptable. Plus, the standard maintenance costs for gas engines tend to be a bit lower than for diesels, and the purchase price is generally lower.

While I like the fact that diesel engines can be equipped with engine braking systems, like Jake brakes or exhaust restrictors, gas engines can also be fitted with exhaust restrictors to increase hill-handling ability. If I were in your shoes, I’d probably go with a gas engine.

In the past, I’ve noted an exhaust gas temperature gauge (EGT), while an interesting accessory, would not really be needed on a stock diesel engine. This prompted several readers to comment on additional uses for the EGT, and I’d like to share them with you.

This is regarding your question about exhaust gas temperature (EGT). We were told at a seminar at Escapade that there is another reason for an EGT gauge on diesels—to protect the turbocharger. If you shut down a diesel while temperatures are still high, the residual oil in the turbocharger can be charred, eventually leading to early turbocharger failure.

We try to always run the engine after stopping until the EGT reads 350 or lower. This usually takes only a couple of minutes but can be a lot longer after a long pull. With all the other gauges and sensors the manufacturer installed on the coach, we were a little surprised at the absence of an EGT gauge. — Tom and Diane


Your article brings to mind another angle on EGTs. We purchased a new Dodge dually, 5.9 Cummins, six-speed manual transmission. It pulls our 1997 Avion 1,500 miles due north through mountains in the spring and back south to Tucson in the fall.

Over the years, on long, gradual climbs in sixth gear, I have often noted that without the pyrometer I would have easily exceeded the 900–1000 degree exhaust temperature limit recommended by Cummins. With the torque and power of that engine, it doesn’t seem to know we are on a climb. In the old days, we had “engine lug” to tell us when to downshift.

Of course, automatic transmissions solve this problem by downshifting, and maybe nobody buys a manual transmission anymore, so the whole story is moot. But, if someone does have one of these new powerful engines and a manual transmission, maybe this bit of experience will help. — Fred

About Mark Nemeth

In 1997, Mark quit his aerospace engineering job and became a full-time RVer. For almost five years he traveled the country while maintaining his website, Mark’s Fulltime RV Adventure ( posting monthly travel logs. Mark now travels part-time and works as the RV Safety Education Director for Escapees RV Club providing technical training at Escapees Boot Camp seminars, as well as assisting in many other areas of the club. He is also technical advisor for Escapees magazine. Learn more about Escapees RV Club at

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