I asked Chat GPT.
Motorhomes can be parked for a VERY time for most people, for some as long as 48 months of the year. Only have a two week holiday twice a year.
What would be the best way to treat it, considering the engine and the whole vehicle?
The biggest mistake people make is
starting it every few weeks for 10 minutes. That's actually worse than leaving it alone. The engine never gets fully hot, moisture builds up in the oil and exhaust, and the battery never really recovers.
My routine for a motorhome that might stand for months would be:
Engine
- Change the oil and filter before long storage if it's nearly due. Dirty oil contains acids.
- Fill the diesel tank completely to minimise condensation.
- Add a good diesel stabiliser if it's likely to sit for over 6 months.
- If possible, drive it for at least 30-40 miles before putting it away so the engine, gearbox and exhaust get thoroughly hot.
Battery
This is probably the most important item.
- Keep both starter and leisure batteries on a quality maintenance charger.
- If there's no mains available, disconnect the negative terminal or fit a battery isolator.
- Don't rely on the solar panel unless it's genuinely keeping the batteries fully charged all winter.
Tyres
Tyres hate standing still.
- Inflate to the upper end of the recommended pressure.
- Move the vehicle half a wheel turn every month or two.
- Better still, park on tyre cushions or boards.
- Avoid standing on wet grass for months.
Brakes
- Never leave the handbrake on for months.
- Use wheel chocks instead.
- Leave the gearbox in Park (automatic) or first gear/reverse (manual).
Fuel
Modern diesel is far less stable than it used to be.
- Keep the tank brim-full.
- Add stabiliser if storing for many months.
- Avoid leaving it nearly empty.
Cooling system
- Make sure antifreeze strength is correct.
- Replace coolant at the proper interval (usually every 5 years or so).
Interior
- Leave cupboards open.
- Prop the fridge door open.
- Remove food.
- Ventilate slightly if secure.
- Use moisture absorbers if stored outside.
Water system
- Drain everything.
- Empty the boiler.
- Empty waste tanks.
- Leave taps halfway open.
Seals
Every few months:
- Wash the vehicle.
- Lubricate door locks and hinges.
- Treat rubber seals with silicone.
Suspension
If you're storing for a year or more:
- Jack stands under the axle can reduce tyre loading, but don't leave the suspension hanging.
What about starting it?
I'd use one of these two approaches:
Best
...
- Leave it alone.
- Keep the batteries charged.
- Then take it for a proper 30-50 mile drive when you're ready to use it.
Second best
- Once every 6-8 weeks, take it out for at least 30 miles.
- Get the coolant to full temperature.
- Get the gearbox fully warm.
- Use the brakes firmly several times.
- Run the air conditioning for 10 minutes.