What Kind of Oil Do Semi Trucks Use? | AMSOIL Synthetic Oils

What kind of oil do semi trucks use is the subject for this blog post. There are two types of choices truckers have. They will either choose to run conventional oils or for the discerning truck who’s interesting in using the best possible lubricants, synthetic oils. There are many competent commercial lubricants on the market, but only a few can claim to offer top-of-the-line quality and performance. Before we get into the differences between conventional and synthetic lubricants, let’s take a brief look at what exactly is a semi truck.

What Exactly is a Semi Truck?

It is a combination of a tractor unit with one or more semi trailers attached to it to carry some sort of freight. The semi trailer is connected to the tractor by means of a fifth wheel coupling, also known as a hitch. There are different types of semi trucks and go by the following names: mid-roof sleeper, flat rook sleeper, day cap, and raised roof sleeper.

A semi truck is a truck or the tractor that has an engine. These semi trucks typically run with or without the semi trailer attached. When they talk about eighteen wheelers, they’re referring to the semi truck and the semi trailer attached to each other. At that point, the total number of wheels combined with both the tractor and trailer unit totals eighteen wheels.

There is a multitude of trailers that can be attached or hauled by semi tractors or trucks. The following is a list of the most typical trailers that are utilized today: reefer trailer, low boy, flatbed, step deck, dry van, power only, Conestoga, stretch double drop, extendable double drop, stretch single drop deck, stretch removable gooseneck, removable gooseneck, multi-car, side kit, and specialty trailers.

Semi trucks are an integral part of our economy and they are crucial in keeping things moving forward. To keep semi trucks running reliably without any downtime and minimizing maintenance and repair costs, it is important for the semi truck fleet operation to carefully consider their lubrication progam. Let’s discuss what kind of oil do semi trucks use and whether there are ways to improve your maintenance program by switching to a superior oil.

Between synthetic oil vs conventional/mineral-based oils, conventional lubricants are derived from crude oil. First, crude oil is extracted from the ground, then sent to refinery plants whereby the crude oil is put through a series of complex refining processes. Obviously, the first and most critical aspect for oil companies is to turn crude oil into diesel fuel or gasoline. After all the diesel fuel and gasoline has been fully processed, they then look to refine the leftover oils to be used as lubricants.

Base stock oils go through rigorous refining to extract and remove as many contaminating elements as possible. Contaminating elements such as nitrogen, oxygen, and sulfur, and metal components like vanadium and nickel are inherently found in oil and the goal is to remove as much of these unwanted contaminants as possible. Unfortunately, at the end of the day, some of these unwanted contaminants are left in the oil and simply cannot be refined out.

This same oil refining process leaves molecules that are similar in weight but dissimilar in structure. These different sized molecules have difficulty flowing over each other and when utilized in a semi truck engine, they tend to flow with an undue amount of fluid friction. Friction generates heat, and over a long period of time, this heat starts to degrade the oil. Not only are contaminants naturally found in conventional oils, but they also contain wax.

When temperatures drop and become cold, the wax in lubricating oils starts to thicken the lubricant. It has been noted by OEM manufacturers that 80% of engine wear occurs during initial cold dry starts. The reason for this excessive wear in engines during cold dry starts is due to the fact that conventional or regular oils do not flow quickly enough to critical parts to protect them from friction and wear. As stated before, the wax found in conventional lubricants causes the oil to thicken and flow too slowly during cold dry starts.

Another aspect to understand about conventional oil is their viscosity index. Viscosity index is a number that specifies how the oil changes its viscosity when exposed to differing temperatures. The higher the number, the less the oil viscosity changes. In other words, a lower viscosity oil will thicken more during cold temperatures and will thin out more during hot temperatures. The higher this viscosity index number, the less the oil changes, or maintains its viscosity grade.

The other type of oils that semi truck operators can choose to utilize are synthetic lubricants. Synthetic lubricants are totally different animals. These high-tech oils are engineered and manufactured in the laboratory. Their chemistry is custom-tailored to eliminate any negative aspects that are naturally inherent to mineral-based or conventional lubricants. They are pure and completely devoid of any contaminants. They are wax-free and are specifically engineered to have a uniform molecular structure. By uniform, we mean that each molecule is exactly the same size. The result is that these same-sized molecules flow easily and efficiently without friction over each other.

A 100% pure synthetic oil offers amazing cold weather flowability. When switching from conventional oils to synthetics, excessive cold dry startup wear is vastly improved due to the fact that this oil instantly travels to critical components.

The question of what kind of oil do semi trucks use depends on whether the goal is to reduce downtime, extend equipment life, improve fuel economy, and lower maintenance and repair costs. If those are goals that you’re interested in, then the type of oil you choose needs to be a high-performance lubricant.

There are a few specialty lubricant manufacturers that are competent in manufacturing lubricants for semi trucks. One particular manufacturer stands out from the rest, and that is AMSOIL. Over 48 years ago, AMSOIL became the first lubricant manufacturer to come out with synthetic motor oil that met the American Petroleum Institute (API) service requirements.

At the time, not other manufacturer was offering such an oil. This was the result of many years of research in aerospace technology. Many independent tests showed it outperformed conventional oils in all categories. They were trendsetters then and now 48 years later they still continue to set the standard in synthetic oil manufacturing. AMSOIL is literally The First in Synthetics®.

AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 15W-40

This 100% pure synthetic oil was specifically designed to outperform all other diesel oils on the market and can help extend the life of semi truck engines.

  • Offers 60% better turbo cleanliness
  • Delivers 2 times better rust and corrosion protection
  • Reduces friction and wear, keeping cylinder linings looking new
  • Provides 6 times more wear protection
  • Delivers 76% less oil consumption
  • Guards against oxidation
  • Maintains viscosity after exposure to high temperatures
  • Superior cold weather flowability
AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 15W-40.
AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 15W-40

AMSOIL Diesel Injector Clean + Cetane Boost

  • Enhances cetane by up to 8 points
  • Fuel economy gains by up to 8%
  • Restores horsepower and efficiency
  • Effective injector cleaning
  • Reduces wear in pumps and injectors
  • Longer fuel filter life
  • Guards against fuel system corrosion
  • Formulated to be alcohol-free
  • Engineered to be safe to use in all diesel fuels, including biodiesel
AMSOIL Diesel Injector Clean + Cetane Boost.
AMSOIL Diesel Injector Clean + Cetane Boost

AMSOIL 80W-140 Long Life Synthetic Gear Oil

  • Engineered for 500,000-mile service life in semi trucks
  • Protects against extreme pressure
  • Guards against rust and corrosion
  • Superior cold-weather shifting
  • Enhanced efficiency
  • Extended seal life
  • Maintains cleanliness
AMSOIL 80W-140 Long Life Synthetic Gear Lube.
AMSOIL 80W-140 Long Life Synthetic Gear Lube

AMSOIL SAE 50 Long Life Synthetic Transmission Oil

  • Custom-blended for manual transmissions that are utilized in high toque, heavy-duty line-haul trucks
  • Resists friction and wear
  • Reduces foaming
  • Reduces heat and temperatures
  • Superior all-weather performance
  • Easier shifting
  • Enhanced fuel economy
  • Longer seal, oil, and equipment life
  • Extended drain intervals up to 500,000 miles
AMSOIL SAE 50 Long-Life Synthetic Transmission Oil.
AMSOIL SAE 50 Long-Life Synthetic Transmission Oil

AMSOIL Synthetic Polymeric Truck, Chassis, and Equipment Grease, NLGI #2

  • Resistant to impact and shock loads
  • Reduces grease consumption
  • Extends greasing intervals
  • Outstanding corrosion and rust protection
  • Superior protection from shock loads and extreme pressure impacts
  • Seals out dirt, water, and contaminants
AMSOIL Synthetic Polymeric Truck, Chassis and Equipment Grease, NLGI #2.
AMSOIL Synthetic Polymeric Truck, Chassis and Equipment Grease, NLGI #2

With the facts presented in this blog post, it is now easier to understand what kind of oil do semi trucks use. Creating a preventative maintenance program that demands the use of superior, high-performance lubricants is a maintenance program that will deliver real benefits. By adding AMSOIL Synthetic Oils to your maintenance program, your semi trucks will operate more efficiently, more reliably, and more importantly, downtime, repair, and maintenance costs will be reduced.

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