Frequently asked questions  

Get answers with our Mobil Delvac™ and Mobil Delvac 1™ frequently asked questions. You can filter questions by topic or product.

Product FAQs - Engine oils

The Automotive Petroleum Institute (API) has established two diesel engine oil specifications – one with backward compatibility for older engine technology ("CK-4") and one for use with newer engine technology ("FA-4"). For more information, see our PC-11 FAQs.

Mobil Delvac 1™ ESP engine oils meet or exceed the requirements of the API CK-4 specification and are backward compatible. These oils also meet or exceed original equipment manufacturer (OEM) requirements for Caterpillar, Cummins, Detroit, Mack and others.

Mobil Delvac 1™ Advanced Fuel Economy engine oil meets or exceeds the requirements of the API FA-4 specification and is not backward compatible. This oil meets or exceeds OEM requirements for Cummins, Detroit and more. Mobil Delvac 1 Advanced Fuel Economy engine oil can only be used in engines approved by the original equipment manufacturer (OEM) for API FA-4 lubricants.


Yes, ExxonMobil stands behind its products. Whether it’s our Mobil Delvac 1 advanced full synthetic engine oils, Mobil Delvac engine oils or ancillary products, we demonstrate our commitment to quality by offering limited warranties. See the warranties.


The latest claims and approvals are available on our product data sheets (PDS).

For quick access, you can scan the QR Code on the product’s label, which will take you directly to the PDS. QR Codes are currently only available on Mobil Delvac 1™ ESP 5W-40 engine oil, but we are planning to expand this convenience to other products in the near future.


For information on where you can purchase Mobil Delvac or Mobil Delvac 1 products, visit our “Where to buy” page. You can find an authorized distributor or truck services near you.


Mobil Delvac 1 synthetic engine oils are fully compatible with their mineral oil counterparts. Mobil Delvac 1 products are recommended for year-round use and can provide improved efficiency and cost benefits.

Please consult your original equipment manufacturer (OEM) application and oil drain interval requirements to confirm you are selecting the correct Mobil Delvac 1 synthetic oil for your equipment.


Mobil Delvac 1™ Advanced Fuel Economy is our most advanced heavy-duty diesel engine oil. This oil meets or exceeds the API FA-4 specification and is designed for latest-generation trucks with friction-modified engine technology.

Mobil Delvac 1 Advanced Fuel Economy engine oil can only be used in engines approved by the original equipment manufacturer (OEM) for API FA-4 lubricants.

To find out if your company’s equipment is a good fit for this product and the potential fuel economy benefits it offers, please provide your information to the ExxonMobil Technical Help Desk by clicking the “Contact us” button on this page (select “Fleets” from the “Topic*” drop-down menu) and a sales representative will contact you.



MD1 chart

*Results may vary based on vehicle/engine condition, driving and environmental conditions. Consult OEM or ExxonMobil before implementing extended ODIs.
Compared to an SAE 15W-40 engine oil. Actual savings are dependent on vehicle/engine type, outside temperature, driving conditions and your current engine oil viscosity.
Relative to conventional 15W-40 engine oil, and within Mobil Delvac 1™ product range. Actual fuel economy improvement dependent on vehicle/engine type, outside temperature, driving conditions and the viscosity of current engine oil.
§As compared to a mineral 15W-40 engine oil. Fuel economy improvements are dependent on vehicle/equipment type, outside temperature, driving conditions and your current fluid viscosities.


We have upgraded the formulations of all our Mobil Delvac 1 engine oils to meet or exceed the API CK-4 and FA-4 specifications, thereby offering outstanding all-around performance.
MD1 chart

*Results may vary based on vehicle/engine condition, driving and environmental conditions. Consult OEM or ExxonMobil before implementing extended ODIs.
Compared to an SAE 15W-40 engine oil. Actual savings are dependent on vehicle/engine type, outside temperature, driving conditions and your current engine oil viscosity.
Relative to conventional 15W-40 engine oil, and within Mobil Delvac 1™ product range. Actual fuel economy improvement dependent on vehicle/engine type, outside temperature, driving conditions and the viscosity of current engine oil.
§As compared to a mineral 15W-40 engine oil. Fuel economy improvements are dependent on vehicle/equipment type, outside temperature, driving conditions and your current fluid viscosities.


Click the “Contact us” button on this page (select “Fleets” from the “Topic*” drop-down menu) and a sales representative will contact you.


Mobil Delvac 1™ Advanced Fuel Economy engine oil can only be used in engines approved by the original equipment manufacturer (OEM) for API FA-4 lubricants.

To find out if your company’s equipment is a good fit for this product and the potential fuel economy benefits it offers, please provide your information to the ExxonMobil Technical Help Desk by clicking the “Contact us” button on this page (select “Fleets” from the “Topic*” drop-down menu) and a sales representative will contact you.

ExxonMobil is proud to showcase our technology leadership by offering a full range of API FA-4 engine oils. We look forward to supporting your advanced lubrication needs.

While an oil’s viscosity is an important characteristic, it actually does not say anything about an oil’s quality; neither does the oil’s color. To be sure you’re buying a quality oil, look at the bottle and ask yourself a few questions: Is the product a reputable brand such as Mobil Delvac™? Do the industry and original equipment manufacturer specifications listed meet the needs of my equipment? Am I buying the oil from a reputable store or distributor? Is there a way to make sure I am buying an authentic product? If you can answer yes to all of these questions, you know you are buying a quality product.



Some people equate cheap oil with the inexpensive cost of operation. But this is a myth. The minute a piece of equipment is filled with an oil, the oil leaves its legacy behind. When comparing a premium product like Mobil Delvac™ to a cheap oil, the cheap oil could lead to higher wear rates and increased formation of deposit, varnish and sludge – all leading to high maintenance costs and reduced equipment life. So, while the cheap oil may cost less to buy, Mobil Delvac oil can cost less to own.

Mobil Delvac engine oils can help to extend the life of your engine. However, the actual life of an engine prior to overhaul depends on many variables: choice of oil, oil drain interval, maintenance practices, terrain traveled, driving habits, fuel quality, load carried and ambient temperature (to name just a few). But using Mobil Delvac oils will certainly help keep the engine life odds in your favor. ExxonMobil stands behind its products; see our Mobil Delvac limited warranties.



While choosing a high-performing product like Mobil Delvac is a great step toward long equipment life, there are other key considerations. To begin with, you need a proper viscosity grade. A full synthetic 0W-20 product may provide significant fuel economy improvement, but it would most likely not run so well in a heavy-duty diesel engine. For that, a 5W-30 synthetic product is needed to provide protection against wear and maintain oil pressure. On the other hand, use of a 25W-60 in a modern, low emissions engine could also lead to premature engine failure since it may be too thick to properly lubricate all components, even at normal operating temperature. A proper preventive maintenance program is also critical to ensuring extended equipment life; this not only means that appropriate inspections, check-ups and work are done but also that they are done at the right interval.
Proper choice of oil, both in the engine and driveline, can have a impact on fuel economy. Two things to consider: A multigrade product tends to provide better fuel economy than a monograde (e.g., a 15W-40 is better than a 40 grade) and lower viscosity products tend to provide better fuel economy than higher viscosity products (e.g., a 5W-30 provides better fuel economy than both a 10W-30 and a 15W-40). As equipment ages, deposits and wear accumulate, resulting in a decrease in equipment efficiency. Mobil Delvac™ lubricants are able to protect the engine against deposit formation and wear, and resist soot-induced and oxidative viscosity thickening, allowing the equipment to maintain fuel economy throughout its life.

Mobil Delvac™ engine oils meet API and ACEA requirements for both gasoline as well as light-duty diesel engines, on top of its heavy-duty credentials. Mobil Delvac oils are formulated to protect a wide range of heavy diesel off-highway vehicles and equipment, including Class-8 big rigs, pickup trucks, diggers, excavators, dozers, graders, tractors, dump trucks and more.

Get all of the information you need by searching the SDS database or the PDS database. Safety Data Sheets (SDS), formerly known as Material Safety Data Sheets (MSDS), and Product Data Sheets (PDS) are important resources for manufacturers, fleets, fleet managers and owner/operators.
Mobil Delvac™ lubricants are formulated with a balanced additive system to provide outstanding performance for equipment. We invest millions of dollars testing our formulations to ensure this performance. Use of an aftermarket additive can easily throw this balance off, potentially causing severe problems. Additionally, many equipment builders now state in their service manuals that they specifically recommend against the use of these aftermarket additives. When you make a decision to purchase Mobil Delvac products, you can rest assured that they are formulated to provide optimal lubricating performance without any need for additional additives.
Regardless of whether you’re moving supplies in the frost of the Arctic, hauling trailers up and over mountains, or traveling in the heat of the desert, synthetic lubricants provide optimal protection in some of the harshest of driving conditions. Synthetic lubricants resist degradation at high temperatures better than conventional oils, leading to long oil life and reduced deposits, sludge, and varnish formation. At low temperatures, synthetic lubricants flow better than conventional oils, allowing them to reach components faster in order to provide quicker and better protection against wear. Because synthetic lubricants impart lower friction properties under load, they can help equipment operate more efficiently than conventional oils. This increased operational efficiency can be seen in improved fuel economy and lower operating temperatures, particularly in axle and transmission applications. In addition, many equipment builders endorse extended oil drain intervals when properly approved synthetic oils are used. In fact, many of world’s transmission and axle builders provide an extended warranty for those using approved synthetic lubricants in their equipment.
Mobil Delvac 1™ synthetic lubricants are fully compatible with their mineral oil counterparts, and it is practical to switch. The outstanding performance improvements of Mobil Delvac 1 synthetic products over mineral oils can be realized at all kinds of ambient temperatures. To realize these benefits, including improved efficiency and cost benefits, Mobil Delvac 1 products are recommended to use all year round.

Product FAQs - Transmission fluid

Get all of the information you need by searching the SDS database or the PDS database. Safety Data Sheets (SDS), formerly known as Material Safety Data Sheets (MSDS), and Product Data Sheets (PDS) are important resources for manufacturers, fleets, fleet managers and owner/operators.

Product FAQs - Grease

For most applications, Mobil Delvac™ Xtreme Grease is recommended. It is a National Lubricating Grease Institute (NLGI) #2 lithium complex grease, designed specifically for use in severe on-road, heavy-duty trucking. It is particularly effective in rust protection. It also has sealing and tacky consistency in dry conditions, and its water-resistant capabilities help reduce lubricant consumption and increase bearing protection in wet environments. Most importantly, it offers very good rust and corrosion protection to help provide long life to bearings and chassis lube points.

Get all of the information you need by searching the SDS database or the PDS database. Safety Data Sheets (SDS), formerly known as Material Safety Data Sheets (MSDS), and Product Data Sheets (PDS) are important resources for manufacturers, fleets, fleet managers and owner/operators.

Fifth wheel trailer mechanisms are subjected to a great deal of sliding and shock loading. Typically, fifth wheel surfaces should be coated with NLGI #2 grease before connecting the trailer. Since the existing grease on the surface has probably already collected dirt and other contamination, it should be cleaned before applying new grease.

Some fifth wheel mechanisms also contain a rack and pinion gear for positioning the trailer. These components often require special greases containing solids such as molybdenum disulfide or graphite so that the contact surfaces continue to be lubricated when the grease is squeezed out. For most applications, we recommend Mobil Delvac™ Xtreme Grease. It is a NLGI #2 lithium complex grease, designed specifically for use in severe on-road, heavy-duty trucking. It is particularly effective in rust protection. It also has sealing and tacky consistency in dry conditions, and its water-resistant capabilities help reduce lubricant consumption and increase bearing protection in wet environments. Most importantly, it offers very good rust and corrosion protection to help provide long life to bearings and chassis lube points.



Weather FAQs - Engine oils

Changing oil performance standards are directly related to continuously evolving emissions and fuel economy regulations. In an effort to obtain cleaner air, the trucking industry must abide by these governmental regulations. That means they are constantly making design changes to their equipment, generally resulting in a harsher environment for the oil: higher temperatures, higher soot loads or even the need to be compatible with after-treatment systems. Bottom line? Low emission engines need higher performing products. Therefore, when emissions regulations change, so do oil specifications. Even if you have an older engine that does not meet the latest emissions standards, it still benefits from oils that are formulated to the latest standards.
Regardless of whether you’re moving supplies in the frost of the Arctic, hauling trailers up and over mountains, or traveling in the heat of the desert, synthetic lubricants provide optimal protection in some of the harshest of driving conditions. Synthetic lubricants resist degradation at high temperatures better than conventional oils, leading to long oil life and reduced deposits, sludge, and varnish formation. At low temperatures, synthetic lubricants flow better than conventional oils, allowing them to reach components faster in order to provide quicker and better protection against wear. Because synthetic lubricants impart lower friction properties under load, they can help equipment operate more efficiently than conventional oils. This increased operational efficiency can be seen in improved fuel economy and lower operating temperatures, particularly in axle and transmission applications. In addition, many equipment builders endorse extended oil drain intervals when properly approved synthetic oils are used. In fact, many of world’s transmission and axle builders provide an extended warranty for those using approved synthetic lubricants in their equipment.
During the winter, all vehicle lubricants – whether engine oil, transmission oil, differential oil, hydraulic oil or grease – should be considered. Before starting equipment in extremely cold temperatures, an operator should make sure the oils in the engine, transmission and hydraulic system are fluid enough to flow. Check the engine oils using the dipstick where applicable; other fluids should also be checked by their appropriate methods.

While most 15W-40 viscosity grades will satisfy the cold-weather startup temperature requirements in the U.S., engine oil specifications should be referenced to ensure that properties such as pour point, cold cranking viscosity and cold-temperature pumping viscosity meet an engine's coldest operating temperature requirements. Advanced full synthetic Mobil Delvac 1™ engine oils are formulated to provide increased cold-weather startup protection even in severe weather conditions. Additional options that fleets or owner-operators should consider are synthetic blends like our Mobil Delvac™ Extreme engine oils.

Engines will experience the highest wear during cold startup, as lubrication to bearings and the upper-engine hardware is limited during startup and initial warmup. The engine oil's viscosity at starting temperature is an important factor in determining whether or not an engine will start.

Using too heavy a viscosity during cold temperatures can result in inadequate lubrication during startup.

If the chosen lubricant has a viscosity that is too high, the oil filter bypass valve – assuming the truck has one – will open and allow unfiltered oil to bypass the oil filter (the bypass valve maintains the lubricating oil flow to the engine and prevents an oil filter collapse). The bypass valve will close as the engine oil warms up and thins out. It is equally important to adequately warm up an engine before loading it. The best practice is to idle for a short period and warm up the engine by operating at a low rpm and load condition.



Many truck engines idle for very prolonged periods during cold winter temperature conditions to allow for warm-up and to keep the cab warm. Prolonged idling will reduce engine life and also waste fuel. Engines operate cooler while idling, and during long idle periods in winter's cold temperatures, moisture in the intake air can condense in the engine crankcase and produce corrosive sulfuric acid, which can attack soft bearing alloys. Long idling also contributes to increased soot and combustion contaminants, which will shorten the engine oil's life prematurely and can lead to excessive piston deposits, sludge formation and detrimental viscosity effects.

Weather FAQs - Transmission fluid

As temperatures drop, the same cold temperature viscosity phenomenon occurs with drivetrain lubricants as it does with engine oils. Following the engine warmup procedures mentioned above will also allow for sufficient oil circulation to your drivetrain components. For general-service transmissions used in on-highway Class 8 vehicles where ambient temperatures of -15 degrees Fahrenheit or below exist, a heat exchanger is recommended to make warm-up times faster. Fully synthetic SAE 50 transmission and SAE 75W-90 gear oil lubricants, such as Mobil Delvac 1™ Transmission Fluid 50 and Mobil Delvac 1™ Gear Oil 75W-90, will provide better low-temperature fluidity than conventional oils, as well as help reduce wear, leading to longer equipment life and allowing for easier gear shifting while operating cold.









Weather FAQs - Grease

Overgreasing the fifth wheel latch mechanism will tend to cause the latching mechanism to operate improperly (latching correctly). This can prevent the latch from locking properly on the trailer king pin and could result in the trailer accidentally dropping. Overgreasing also makes the fifth wheel latch difficult to operate during cold temperatures, which drivers often complain about.

A truck's greased components are subjected to more adverse conditions during winter weather conditions. Adequate grease is critical to ensure long component life and to keep out contaminants. Since grease is harder to pump and flow under cold temperature conditions, it is important that truck shops ensure their grease equipment is maintained and adjusted properly to ensure good pumping pressure and grease flow through the entire grease-dispensing system to the grease gun nozzle. Any leaking lines, hoses or grease guns should be repaired or replaced. Air pressure to the grease pump must be adjusted to ensure good grease flow and pressure to the vehicle’s greased components. Technicians should also visually ensure clean grease is purged through all outlets of the components, such as all trunnions on a u-joint.

Truck or trailer units utilizing on-board automatic grease-dispensing systems should ensure the proper grease product is being used to ensure good flow under cold temperature conditions and the lubricator is adjusted to provide adequate pumping under cold temperature conditions as the grease will be harder to pump as temperatures decrease. Inadequate flow will lead to early component failure. If the current grease product is not performing under cold temperature exposure, consider dropping to a lower NLGI grade and consult your lubricant supplier.

During winter weather conditions, vehicle suspension components can be subjected to more adverse conditions, such as increased water and contamination from road salting. Careful attention is needed to ensure that the suspension components are greased at a regular interval and the proper amount of grease is applied to help minimize the entry of road contaminants, and to replace grease that has been washed out due to excessive water exposure. It is also important not to overgrease components as this can rupture seals and lead to reduced component life. A ruptured seal can lead to loss of grease and lack of lubrication as well as intrusion of road contaminants, water, dirt, etc.

Differentials and wheel hubs can be exposed to increased water intrusion during winter months from wet road conditions, high water at curbs, road flooding, etc. The lubricant condition should be inspected for water contamination when levels are checked. A visual inspection that shows a hazy or cloudy appearance or visible water droplets can indicate an excessively wet lubricant. Any indication of water intrusion should be investigated for the cause and the lubricant changed.

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