Motorhome Oil Basics

Do you know what type of motor oil to add to your motorhome engine? Here’s an overview of the basics you should know about the types of oil to use in your motorhome.

Synthetic Motor Oil
Few drivers are concerned about the science behind the formulation of motor oils, but most want to know how the lubricants will benefit them. Synthetic lubricants, when compared to conventional motor oils, offer critical performance benefits, including:
–    superior protection in low temperatures, enabling easier and faster start-ups in cold weather (as low as -40 degrees F);
–    enhanced high-temperature durability, reducing oxidation and wear on critical engine parts (up to 400°F);
–    reduced oil consumption under high-speed conditions;
–    superior performance under heavy engine loads/stresses, such as hauling and towing; and
–    increased stability and better control of deposits that can impede flow and lead to higher wear.

A common misunderstanding is that synthetics should be used only in new vehicles and not older engines. Another myth is that synthetics can destroy seals. Yet another misconception is that new engines require a break-in period with conventional oil, and only then can you switch to a synthetic. Some people also believe that a special oil filter is required. Although a high-quality filter is recommended, you can use the same type of filter that you would with conventional oil.

Oil Labels
Here’s how to decipher diesel-engine oil labels. Take a motor oil labeled CI-4 oil, for example. This is an American Petroleum Institute quality and service designation.
–    The “C” is a service category for Compression-ignition (diesel) engines.
–    The “I” is a quality designation and is the most current for low-emission engines.
–    The “4” relates to four-stroke engines. Be sure to use an oil grade recommended by your engine’s manufacturer.

CJ-4 Oil
All diesel engines used in motorhomes that require ultra low sulfur diesel (ULSD) fuel must use API classification CJ-4 motor oil. This oil is specially formulated with low sulfur for use in these engines, yet it also can be used in earlier diesel engines.

Oil Filter
Change the oil filter every time you change the oil, using a high-quality filter. Fill the new oil filter almost to the top before putting it on after an oil change (and before the engine is started). This keeps the engine from running without oil pressure while the oil pump fills up the new filter.


  1. I have first hand knowledge that synthetic oil is not suitable for older engines. I have rebuilt several Porsche 911 engines from the 70’s using OEM gaskets and seals. The people that switched to synthetic oils after the rebuild ended up with several oil leaks mostly from oil seals. As if the 911 engine didn’t have enough places for oil to leak from. The main seal seemed to be the hardest hit. I had to pull several engines and transmissions to replace these seals. There are now updated seal kits that are Ok to use with synthetics. Do your homework. I have read lots of articles on oils for older engines. The consensus is that shell rotella 10w-40 fits the bill for older engines and has specific additives that aid in lubricating the flat tappet valve trains of these engines. I know its typically used in diesel engines but i use this in my 1965 Mercury Comet with good results.
    Thanks Tom


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