How much should a deisel be driven

[Jason Worman]

So we have a Cat 3126 engine 8n our 91 Contessa. There are roughly 77k on the odometer. We live in it fulltime. I have heard various amounts of miles and hours it should be driven. Any thoughts or opinions how much we should drive it each month to keep it in good working order. Thanks

[Steve Huber Co-Admin]

Jason,
IMHO at 77K you've barely broken it in. Your engine is probably good to at least 500K miles. Don't worry about running it. Best for it is to run it long periods and mileage. Short hops where the engine doesn't get up to operating temperature should be avoided if possible as this can result in moisture building up. Also don't shut it down immediately after running it at normal RPMs. Let it idle for a minute or so for the turbo to slow down. Just be sure to keep up with recommended maintenance.
Steve

[Mike Shumack]

I think one of the biggest problems with not use a coach much is the fuel in the tank never gets used. Diesel fuel has a long shelf life but if it is going to sit in the tank for months a fuel additive should be used to prevent the growth of microbes. such as https://powerservice.com/find-my-product/#2 - but there are plenty of brands to chose from.

[Peter and Connie Bradish]

We are at 287,000+ miles on our Cummins 8.3L engine. The problem for these engines is maintenance and not using them. They are designed to run many hours and every day. As Rvers we don't use them like a trucker would. So if you are sitting in one place for weeks on end you might think about running the diesel engine and the generator at least once a month. As stated letting the diesel fuel just sitting for many months also can cause a problem. There are biocides which help kepp out biological growth but there is also the shelf life of the fuel.
So the real problems are too little use of the engine and failure to maintain the engine.

[Jason Worman]

The other question I have is should we keep the fuel tank full all the time? Thank you everybody for all the input.

[David T. Richelderfer]

In cooler/wetter weather and/or if the coach will be sitting for an extended period, then the diesel tank should be kept full.  Condensation of water vapors in cooler/wetter weather conditions will introduce liquid water into the tank... which can cause any of several problems.  A more full tank with diesel will leave less unfilled tank volume for water vapor resulting in less condensation.

[Gerald Farris]

Jason,
Like Steve said, the key to engine use is how it is used. If you are going to use the engine under a load at operating temperature (driving), that will be beneficial, but cranking up the engine and letting it idle is not. So unless you are going somewhere, starting it and letting it idle is not advisable. The same thing goes for your generator, if you are going to "exercise it", run it under a load by turning on A/C units or electric heaters depending on the weather, because you are not only heating up the generator engine but you also heating up the generator section to avoid moisture problems.

Gerald

[Mike Shumack]

The other question I have is should we keep the fuel tank full all the time? Thank you everybody for all the input.

Tank should be kept full so condensation can't form on the inside walls of tank.

[Dave Atherton]

Gentleman good morning, this is a very good subject, one of the biggest problems with a
Diesel Pusher motorhome they need to be run including the diesel gen set. Sitting in storage
or camp ground for several months. Engine needs to be started and run until thermostats open
and coolant is running temperature. The Diesel engine needs to work getting engine temperature
running temperature ( thermostat opening on Caterpillar 191 deg f and full open 206/208 deg f
That is the way your engine test spec before shipping. Same goes for engine intake manifold
Temperature 110 deg f on lower hp range engines to 122 deg f on bigger engines. You also need the engine temperature at operating range for BIO fuel to work like the trucks. Looking for replacement
Used motorhome buyer in most cases will buy lower miles thinking long life trouble free. This
Is everyone own choice but buying a diesel pusher with high miles is the Best Buy (Reason engine
has not set) and everything is running. Min miles to break in your Diesel engine 100,000 miles.
any way you look at your Diesel engine you will not wear it out . Problems on the road today falls
under different reasons for extreme high repair bills that not related to owning a problematic engine
to justify repairs.  Dave Atherton Retired Cat Mechanic

[Jason Worman]

Thank you for the great information