RV Recommended Oil Weigh

Realizing just how important engine oil is can help prevent the occurrence of problems now and while you are on the road.

Engine oil has numerous functions. It helps to cool, clean, seal lubricate and protect against corrosion and rust in engines.

Just a little bit of oil can ensure that spinning parts are kept separate from the stationary parts in a bit to prevent friction caused by metal to metal contact.

This type of contact can cause surfaces to wear away. This article aims to highlight the functions of oil and to also help you discover what the recommended oil weight for your RV is

The function of oil in an RV

Oil helps to cool the engine down by absorbing the heat created by moving parts. It then transfers this heat into the oil cooler located in the radiator where it gets diffused thanks to the air around it.

Additionally, oil is splashed onto the bottom part of a piston in a bid to aid heat transfer. If this heat transfer does not take place, the pistons could expand while inside the cylinders causing untold damage.

Oil can also be used to get rid of any grit particles that might enter the engine via the air cleaner. These bits of dirt, metal, and unknown particles are collected and then deposited into the oil filter to ensure that damage does not occur.

When an engine is properly lubricated, fuel economy increases, friction is reduced and that engine’s lifespan is extended given that oil cushions the moving parts correctly.

Oil can also help seal up the cylinder walls and piston rings to ensure that compression is maintained. It also prevents air from touching the engine’s steel parts which could cause rust or oxidation.

What to look for when purchasing engine oil for your RV

When purchasing oil for your RV, you will notice that the bottle or tin has some numbers and markings. Some of these markings which are usually at the top of the bottle have to do with the API or American Petroleum Institute service ratings.

These ratings are ranked from the lowest oil quality SA to the most innovative synthetic oils SJ suitable for engines that have turbochargers.

When it comes to purchasing oil for your RV, it is always best to have a look at your owner’s manual. This is because using the recommended oil rating has the best chance of maintaining your engine’s warranty.

Nevertheless, this is not set in stone. It is possible to use a better oil rating for your RV, but you should never use one with a lower rating.

Performance properties and service ratings

These are typically expressed by two letters, with the first letter highlighting the kind of engine that oil is suited for.

Engines powered by gasoline are indicated using S as the first letter. Diesel engines start with C. The second letter is used to indicate the oil’s performance rating with the letter A to M used.

Weight and Viscosity

The oil weight or viscosity refers to the measure of an oil’s fluidity. When an engine oil has a higher number it means that it is heavy oil.

When the oil is given a lower number such as SAE 10 or 5, it means that it flows quite seamlessly, especially in cold weather. The abbreviation SAE stands for Society of Automotive Engineers.

As stated earlier, it is best to follow your RV manufacturer’s recommendation for oil viscosity and weight. Using an incorrect oil weight could result in a reduction in power or woeful fuel economy. 

Typically, all-season or multi-grade oil like 15W-40 is used. This oil has the 15 weight when the RV is started up in cold conditions, whilst offering the protective properties associated with 40 weight oil in higher temperatures.

To break it down in layman terms, the closer the first number to 1, the more viscous or fluid the oil is during low temperatures. With a higher number, it means that the oil can better perform at high temperatures.

Why do you need an oil that has these properties?

During cold weather oil tends to thicken, causing it to resist flowing. This can cause your RV’s engine to become hard to turn on. It could also cause inadequate lubrication until the engine is warmed up.

When the weather is hot, the oil becomes thin, making it unable to provide the necessary lubrication requires. This can result in damages to the moving parts. It is for these two reasons that all-season oils are preferred.

It can act as an easy flowing, thin oil when the temperature is cold, but as the engine becomes warmer act as a heavier oil to offer protection to the engine’s moving parts.

While it is always advisable to use your RV manufacturer’s engine oil weight, there are certain older engines with higher mileages that can benefit from using a heaving weight oil.

The oil can be used to lubricate and seal parts that may have visible signs of wear. Using a heavier oil in this scenario can help to stop oil from passing through worn-out piston rings when deceleration occurs. 

Mineral or Synthetic based?

During low temperatures, synthetic oils come into their own as they flow better and are wax-free. Synthetics also contain additives that can help reverse chemical changes or breakdowns that cause sludge to form.

Sludge can block the galleries (or tiny passages located in the engine head and block) which oil uses to lubricate moving parts. This can help stop oxidation, the creation of air bubbles, and gumming resulting from oxidation.

Air does not help keep the moving parts from one another. Synthetic oils can enable the differential and engine to run a lot cooler, causing the miles between oil changes to get longer.

Numerous new vehicles rolling off the factory floor tend to have synthetic oil in their rear differential and oil pan. Magnesium and calcium detergents found in the oil can help clean the engine. Dispersants in synthetics can also keep dirt and sludge away from the moving parts till collected in the oil filter.

While the costs associated with synthetic oils are higher than those of mineral-based oils, the majority of RV owners state that it is an expense that provides them with performance gains and long term savings.

The greatest advantage of synthetic oil is that there can be more miles before the oil needs to be changed. Nevertheless, this can be taken for granted and has caused some criticism, as some drivers might neglect their routine oil change simply because they are using synthetics.

As an RVer, you must maintain your routine oil change so you do not negate the advantages of using a synthetic provides.


Irrespective of the oil you select for your RV, routinely changing it can be the most inexpensive and easiest method of preventative maintenance your RV can get.

If you choose to change the oil yourself or have it done by a professional in an auto shop, ensure that you can effectively track the changes. If it helps, place a maintenance log in your RV, so you can always be aware when your next oil change should be.

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