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White smoke from exhaust

I have a 1998 motorhome built on a heavy duty Ford chassis. When I first start it after not driving for a few days I see white smoke coming the the exhaust tail pipe. I can’t tell whether it continues as I drive, but it is no longer there when I arrive at my destination. I added a can of fuel additive about 2 weeks ago, but haven’t seen a change. Can anyone tell me what might be causing this and what I should do about it? Thanks!

You need to check to see if you are losing coolant. This could be a bad head gasket. If you keep running the motorhome you could ruin the engine - see the thread about the '97 Ford F-150 that won’t turn over.

Motorhomes are very hard duty for a motor so a bad head gasket is very possible. Since this white smoke hasn’t been the norm for the vehicle, you need to check this out. Putting in fuel additive doesn’t really make any sense, so no change in the smoke means you have to really get the motor checked out. A mechanic can do compression checks, leak down tests, and look at your coolant and oil for clues about what is causing the smoke.

White smoke is usually water or coolant. The reason you see it at start up is the motor is cool as the motor heats up and the exhaust system heats up the water (coolant) is vaporized more and you don’t see it as white smoke anymore. It is still coming out, you just don’t see it.

You should watch the coolant and the condition of the oil as UncleTurbo suggested. (Of course, you should always do that whether you suspect a problem or not).

But there’s a good possibility that this is just normal. When the vehicle sits all sorts of condensation builds up. The first thing that happens is it gets burned off. Then it goes away once everything is all heated up & the condensed moisture has been burned off.

White smoke that presents in cool temperatures or high humidity that goes away in a minute or two after starting is just vapor, condensation in the exhaust system that burns off as your exhaust system heats up. Like dew on your lawn in the morning, it burns off. I like cigroller’s answer that this might just be normal.
A failed head gasket might never leave a trail of vapor but you would lose coolant. Or a failed head gasket might allow radiator fluid into a combustion chamber. In which case, the white vapor coming from your exhaust would be very noticable in any weather, and would not stop when the car warms up, but would get much worse. You’d be that car that creates actual dangerous conditions for the cars following. There’d be heavy plumes of vapor coming from your exhaust. Your engine wouldn’t last very long in this condition: it would overheat quickly and the CEL would flash like crazy, telling you to pull over and shut off the engine ASAP.
This doesn’t sound like your problem. It may be that you’re at the first stages of this problem. and it will get worse. If you have had the coolant system flushed recently, using anything but water, you may have damaged the head gaskets.
If not, see if the condition does get worse, check your coolant level is reduced, and if not to either, it’s normal.