Guide to RV maintenance fluids and filters

Guide to RV Maintenance Fluids and Filters

Updated on December 26th, 2023

Sitting on the roadside with RV engine problems is a genuine threat when you fail to keep up with regular maintenance of fluids and filters.

Knowing what RV fluids and filters need attention and when to perform service is critical to prevent engine damage that quickly sidelines your camping fun.

You can stay on task by following this guide to RV maintenance fluids and filters. Inside, I detail what to check, fill, flush, and replace, what to DIY, and what to leave to professionals.

By the end, you’ll never overlook important engine care and keep your RVing adventures on track!

Guide to RV Maintenance Fluids and Filters

Owners of motorhomes have an extra burden on recreational vehicle maintenance since these RVs also come with an engine that needs to run efficiently.

RV Engine Fluids – What You Need

Here are the six different fluids you’ll need to monitor on all Class A motorcoaches, Class C motorhomes, or Class B campervans:

  • Oil
  • Brake Fluid
  • Transmission Fluid
  • Radiator Fluid
  • Power Steering Fluid
  • Windshield Washer Fluid

Motorhomes with power leveling jacks will need to check the hydraulic oil level.

RV Engine Filters – What You Need

An RV engine filter

Always remember to change out these filters on your motorhome:

  • Air filter
  • Oil filter
  • Fuel filter
  • Power steering and transmission filters

A dirty air filter chokes off the oxygen the engine needs to run efficiently. Change the air filter at the same time as your oil filter during routine maintenance fluid changes.

If you’re changing the air filter yourself, make sure you place square filters in fin-side down, or it’ll clog up fast.

Oil filter replacement isn’t tricky to DIY, but the filter will require crawling under the RV.

Depending on your motorhome type, you’ll need to change out your fuel filter every year or so. Check out this video for more on DIY fuel filter replacement.

Power steering and transmission filters are often inline components that require some finesse to remove and change. Take them to a shop for replacement during routine flushes.

Motorhome Engine Oil

A man changing the oil

Any handy person with the right tools can perform DIY motorhome oil changes, but it’s much easier and not much more expensive to take it to an oil change service center.

Be aware that changing RV oil at any campground is nearly always against the rules.

Locate the oil dipstick in your engine compartment by referencing the manual or looking for a tiny cap with a loop on top. Keep looking nearby for a secondary oil-fill port that has a cap marked “oil.”


  • Pull out dipstick
  • Clean off with a paper towel or rag
  • Reinsert dipstick
  • Pull out again and check level
  • Add oil if level is below “full”
  • Recheck level with dipstick


Every type and age of gas or diesel engine may require a different type of oil. The weather where you plan to RV also plays a role in the viscosity of oil you should use.

Full synthetic oil is a good choice because it’s purer and can tolerate temperature extremes better than conventional oil.

Conventional oil is cheaper, and some RVs require it.

Because there are many engine oil variables, there’s no one brand or type to suggest as the best motorhome engine oil. For diesel engines, Castrol 03087 Edge Extended Performance 5W-30 gets high marks, while the Pennzoil Platinum Full Synthetic Motor Oil 10W-30 is a good one for gas engines.


5W oil is thinner and best for cold climate RVing. 10W or 20W are best for hotter region RVing.

If the oil on the dipstick looks very dark or gritty, it’s time to get an oil change as soon as possible to avoid engine damage.

Motorhome Transmission Fluid

You can change your motorhome’s transmission fluid yourself, but rarely will you achieve a complete drain as you would by taking it to a shop.

This fluid service requirement doesn’t need to happen as often as an oil change. Save the hassle and take your RV to a certified RV mechanic.

When you feel the gears shifting roughly between gears or slipping while driving your coach, the transmission fluid could be the issue.

Leaks are easy to detect as the fluid is either pink or translucent red. If your RV does have a leaky transmission, you can top off the fluid until you fix it.

Look for a red-capped dipstick in your engine compartment. Some engines will have a separate filling port, while others will have you add transmission fluid through the dipstick tube.


  • Make sure your engine is warm before checking the level
  • Pull out dipstick
  • Clean off with a paper towel or rag
  • Reinsert dipstick
  • Pull out again and check level
  • Add fluid if level is below “full”


Your motorhome’s manual will tell you the amount and type of ATF to use.

Putting in the wrong type of RV transmission fluid for a gas or diesel RV won’t lubricate properly and cause costly engine damage.

Change Transmission Fluid (Video)

Motorhome Radiator Fluid

Your Class A, B, and C motorhome’s radiator requires an antifreeze or coolant liquid to help cool the air inside the engine. You can easily DIY a top-off of fluid, but take the RV into a shop for the regular full-flush.

Low levels of radiator fluid or a total loss from a leak will quickly lead to engine overheating and failure, so monitoring this fluid is crucial.

Locate the radiator fluid cap at the front of the engine compartment. The cap is often marked “engine coolant.”


  • Wait for engine to be cool or lukewarm, never hot
  • Park on a level surface and turn off engine
  • Open radiator cap on top of unit by pushing down and turning
  • Peek into the opening and check the level
  • Find the “fill” line etched on the inside tube
  • Add fluid to reach this line, or if no line fill to about 1.5 inches from the top
  • Replace cap and ensure you turn it so it locks into place

NOTE: Some RVs will have a radiator cap and a secondary coolant expansion tank with a filling port. If there’s a secondary tank, open the lid and fill the fluid here.

Be aware that this tank should appear nearly empty (leaving room for expansion as the fluid heats up).


For diesel motorhomes look for an Extended Life Coolant (ELC) such as Valvoline Xerex and for gas-engine motorhomes you can also use AC Delco Dex-Cool.

In an absolute pinch, you can use plain water in your radiator if it’s low and overheating, but this is only a stop-gap measure until you can reach a service station for a proper fluid refill.


Always place a rag over the cap before opening and maintain a downward force during removal. You don’t want the cap to come flying off and possibly send scalding fluid into your skin.

If your RV has an overflow tank and the coolant is full but low in the radiator after the RV has been sitting for a few hours, it’ll need immediate servicing as there’s a clog in the system.

If your engine heat indicator on the dashboard is running high (mid-way is what you want), check your radiator fluid after the engine cools down.

Motorhome Power Steering Fluid

Anyone should be able to handle a DIY motorhome power-steering-fluid refill. A complete flush is better left to the experts during a scheduled maintenance service appointment.

Check the owner’s manual for the filling cap and dipstick location, or take a good look around the RV engine to spot the cap that says “power steering” on the top.


  • Pull out dipstick
  • Clean off with a paper towel or rag
  • Reinsert dipstick
  • Pull out again and check level
  • Add fluid if level is low but do not exceed the “max fill” line


Many RV motorhome manuals will indicate which brand or type of fluid they recommend. Always use this fluid to avoid issues with steering performance and service warranty.

Conventional power steering fluid is typically clear or transparent and darkens as it ages. You can also buy synthetic power steering fluid that can enhance performance in extreme weather conditions.

If the fluid in your power steering reservoir is red, then it’s an ATF (automatic transmission fluid), or if it’s brown, it can be an AW46 hydraulic oil or 15W40 engine oil, which both are suitable for this application. Some tanks will have a sticker that indicates which specific fluid to use.


Take notice of small differences you feel in your motorhome’s steering wheel and performance while driving. A harder-to-turn wheel or strange noise can indicate a problem, which this article on power steering issues fully details.

Consider using a power steering brand that offers leak stop protection that can plug small leaks before they cause significant problems.

Old power steering fluid will look brown, as shown in this video, so don’t assume all brown-looking fluid is oil. If you’re unsure, suck some up with a turkey baster and bring it to a mechanic for a professional opinion.

 How to Change the Power Steering oil and Filter (Video)

Motorhome Windshield Washer Fluid

The easiest and least expensive DIY motorhome fluid refill is going to be the windshield washer fluid.

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The reservoir is typically a transparent white so you can visually see the level of liquid inside. The wide cap is easy to remove for filling.

Look for the windshield washing fluid tank near the front or sides of the engine compartment where it’s easily accessible.


  • Visually look at the markings on the side of the tank
  • Open cap and add fluid if the level is low
  • Never add fluid past the “max fill” line


Miles on the road with the expansive windshield found on motorhomes means your windshield will get covered in bugs and dirt, so a watery, cheap fluid isn’t going to work.

Look for Prestone AS658 All Season as a top choice for refilling your reservoir. The deicing agents can clear away snow and ice during cold-weather camping trips, while the bug wash detergents can break up sticky residues that can smear across the glass in all seasons.

A quality window washing fluid can make a huge difference in eye strain while driving, so don’t skimp on this motorhome necessity. Check the level every few times you fill up on gas to ensure it stays full.

Motorhome Leveling Jacks (and Slides) Hydraulic Fluid

Checking and adding hydraulic fluid to your RV is a straightforward DIY chore.

I suggest letting an RV service technician handle the complete replacement of fluid.


Your hydraulic fluid reservoir location inside your engine compartment will vary depending on the class of your motorcoach and the manufacturer.

A quick check of the manual should lead you to the right area. Be prepared with a funnel with a long hose in case the tank is hard to reach.

Many hydraulic-fluid reservoirs will be a black tank that holds around a gallon of fluid.

The cap will unscrew and have a dipstick attached. The markings on the dipstick will allow you to determine if you need more fluid.


  • Pull out dipstick
  • Clean off with a paper towel or rag
  • Reinsert dipstick
  • Pull out again and check level
  • Add fluid if level is below “full”


Before buying any brand and type of hydraulic fluid for your camper, check your owner’s manual for recommendations.

Most experts and manufacturers say to use an ATF with low-viscosity for motorhome hydraulic jacks. Dextron III or Mercon are names to look for on a label.

The name “Mercon” on a recommended ATF fluid comes from Ford patents and means the manufacturer wants a specific level of quality that will support the jack’s function and lifespan.


Don’t ever switch to a synthetic brand if your motorhome came with and recommends a conventional fluid and vice versa. Mixing fluid types can cause it to gum up.

Never add fluid to the reservoir unless all RV jacks and slides are retracted. If you fill the tank with them out, the fluid has nowhere to go when they retract but out the cap or by blowing a line.

Flush and replace your motorhome hydraulic fluid reservoir every three years.

Final Thoughts

Motorhomes provide so much camping enjoyment they’re worth the extra work to keep them running strong.

Use the guide above along with the information in your owner’s manual to create an engine maintenance fluids and filters checklist.

A list with all the brands and quantities of supplies you need each RV season will help you never miss a critical engine maintenance task!

"Man cannot discover new oceans unless he has the courage to lose sight of the shore."
-- Andre Gide

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