When to change oil

When to change oil, how often should i change my oil, what type of oil should i use. These questions can be simply answered after you read this information and know the truth about this synthetic oil.

Synthetic oils mean fewer oil changes, long-term savings and convenience.

Deciding when to change oil can save you money and time, with less wear on parts.

Despite growing evidence that even conventional motor oils perform past 3,000 miles, and that synthetic motor oils have an even greater service life, many oil companies still recommend the 3,000-mile oil change as a way to protect their bottom line. AMSOIL always has formulated its synthetic motor oils to the highest possible standard and recommends the oil change intervals because nearly 40 years of experience has shown AMSOIL extended-drain synthetic motor oils are effective for extended oil change intervals in normal service.

Many AMSOIL users find the extended-service capabilities of AMSOIL products very attractive and have used AMSOIL products accordingly for many years. Their vehicles and equipment run great and last a long time. In fact, the AMSOIL archives contain records of passenger car engines with extremely high mileage – up to 930,599 miles in which AMSOIL products and extended service intervals were the rule.

Q & A: Synthetic Oil Basics and Switching From Petroleum to Synthetic

What is the difference between synthetic and conventional oil?

What roles do additives play in motor oil performance?

Can synthetic oil be used in new engines?

What is the difference between synthetic and conventional oil?

Oil, whether synthetic or petroleum-based, consists of molecular chains of hydrogen and carbon atoms, referred to as hydrocarbons. Petroleum crude oil is a thick, highly flammable dark-brown or greenish liquid with high energy densities. Many contaminating elements exist in this complex mixture of hydrocarbons, including sulfur, nitrogen, oxygen and metal components such as nickel or vanadium. Petroleum crude oil is the raw material used for a wide variety of petrochemicals, including solvents, fertilizers, plastics and lubricants.

The oil refining process separates the various types of molecules in the oil by weight, resulting in a concentrated batch suitable for today’s uses such as gasoline, LPG, kerosene or base oils for lubricants. The chemical composition of conventional motor oil can vary substantially and depends on the raw crude oil refining process.

While petroleum base oils are refined, synthetic base oils are manufactured and can achieve a higher performance level. Synthetic oil is chemically engineered for a certain molecular composition with a tailored and uniform structure. Such fine-tuned control over the final molecular composition of synthetic oils is the key to the superior performance properties of these fluids. Designing molecular structures in a planned and orderly fashion results in molecules, and end-products, that are far more stable than their refined petroleum counterparts.

Base Oil Groups

The entire range of base oils, including conventional petroleum products, are divided into five groups based on the level of saturates (saturated molecules), sulfur and viscosity index. In general, the chemical composition and performance properties of the base oil categories improve with advancing group number. For instance, Group I has a lower concentration of saturates than Group II, while Group II has a lower concentration of saturates than Group III base oils. Today, Group III, Group IV and Group V base oils are considered synthetic.



Saturated molecules contain a higher percentage of carbon-hydrogen (CH) bonds, which limits the available sites to which other, harmful molecules can attach. When other molecules, such as oxygen, attach to oil molecules, they break down the molecular composition of the oil and weaken its performance. Saturated molecules are beneficial in lubricating fluids because they remain stable longer, resulting in a more durable lubricant. Unsaturated molecules have fewer single carbon-hydrogen bonds and are therefore less stable.



Sulfur is a naturally occurring, inorganic element that readily reacts with oxygen molecules and is detrimental to oil performance. Synthetic base oils have less sulfur than conventional base oils.
Viscosity index refers to the temperature-viscosity relationship of lubricating fluids. Oils with a high viscosity index (VI) are less affected by temperature; those with low VI are affected more. Oils with a VI less than 120 (Groups I & II) are more susceptible to viscosity variance because of temperature. The viscosity index of synthetic base oils is higher than that of conventional petroleum base oils.

Viscosity index refers to the temperature-viscosity relationship of lubricating fluids. Oils with a high viscosity index (VI) are less affected by temperature; those with low VI are affected more. Oils with a VI less than 120 (Groups I & II) are more susceptible to viscosity variance because of temperature. The viscosity index of synthetic base oils is higher than that of conventional petroleum base oils.

Pure, Uniform Molecules Form Strong, Stable Lubricants

Petroleum oils have molecular structures that are randomly organized and, consequently, have limited performance abilities. Their varied and inconsistent molecular structure results in less film strength and lubricity. Their paraffinic wax content also makes them more susceptible to viscosity variance and cold-temperature flow problems.

On the other hand, synthetic base oil molecules are chemically controlled, which provides increased film strength and lubricity over petroleum oils.

The performance qualities of base oils have a marked impact on the performance qualities of the finished product. Synthetic base oils provide key features and customer benefits including better wear protection, more horsepower, increased engine cleanliness, improved fuel economy, easier cold starts and longer oil life.

What roles do additives play in motor oil performance?

Most lubricating oils have other chemicals added to improve the overall performance of the fluid. Chemical additives are used to enhance the beneficial properties of the base oil or to make up for oil deficiencies. For passenger car motor oils, base oil makes up 70 percent to 80 percent of the final product; the other 20 percent to 30 percent is comprised of additive chemistry.

Additives help lubricants stand up to extreme operating environments. Even the best base oil would not be able to protect as well against the effects of heat, shearing forces, chemical and water dilution, corrosion and wear particles. In short, additives make good base oils even better. They give good base oils the performance benefits consumers have come to expect, such as multi-grade performance, extended drain intervals and extreme-pressure performance.

Anti-wear Agents chemically react to form a film barrier that prevents metal-to-metal contact and wear.

Antioxidants reduce the tendency for oil to react with oxygen and reduce sludge buildup.

Dispersants help to suspend and disperse contaminants in the oil to keep engine surfaces free of sludge and deposits. They fight the build-up of corrosive acids and are most efficient at controlling low-temperature deposits.


Detergents help to suspend and disperse contaminants in the oil to keep engine surfaces free of sludge and deposits. They are most efficient at controlling high-temperature deposits.

Extreme-Pressure Additives coat metal surfaces to prevent close-contact components from seizing under extreme pressure. They are activated by high temperatures and high loads to react with the metal’s surface to form a sacrificial wear layer on components.

Foam Inhibitors reduce the surface tension of air bubbles and causes them to collapse.


Friction Modifiers can be used to give oil more ‘slippery’ characteristics. In engine oils, friction modifiers are used to increase the oil’s lubricity for the purpose of reducing friction and improving fuel economy.

Pour Point Depressants give high-viscosity oils good low-temperature properties. Pour point depressant polymers inhibit the formation of crystals to minimize low-temperature viscosity increase.

Rust & Corrosion Inhibitors form a protective barrier over component surfaces to seal out water and contaminants. While most rust and corrosion inhibitors work by forming a physical barrier, some rust inhibitors function by neutralizing acids.

Viscosity Index Improvers are long-chain polymers that help control the viscosity of multi-grade engine oils. They expand and contract as temperatures vary. High temperatures cause VI improvers to expand and reduce oil thinning; low temperatures cause the VI improvers to contract and have little impact on oil viscosity.

Use this link to get the recommendations for YOUR car, truck or SUV. Just add the recommended products to the shopping cart and have then shipped to your home in 2 days. CLICK HERE

3 Levels of High Performance Motor Oils - 25k, 10k & OEM

AMSOIL Signature Series Line (25 k mile/1 yr drain interval)

AMSOIL 0W-20 (ASM), 5W-30 (ASL) and 10W-30 (ATM) Synthetic Motor Oils join AMSOIL Signature Series 0W-30 to round out the Signature Series line. Signature Series 0W-30 is now identified by product code AZO.

In addition to being reformulated to meet the latest API SN Resource Conserving and ILSAC GF-5 industry specifications, the new Signature Series line features all-new packaging and represents the very best motor oils AMSOIL has to offer, allowing motorists to take advantage of maximum extended drain intervals. In the interest of consistency and clarity within the Signature Series line, all four motor oils are recommended for drain intervals of up to 25,000 miles/one year, whichever comes first (15,000 miles/one year in severe service conditions).  Click to see 25 k mile oil page.

Use this link to get the recommendations for YOUR car, truck or SUV. Just add the recommended products to the shopping cart and have then shipped to your home in 2 days. CLICK HERE

AMSOIL XL Synthetic Motor Oil may be used for up to 10,000-mile/six-month (whichever comes first) oil change in normal service, or longer when recommended in owners’ manuals or indicated by electronic oil life monitoring systems.

Use this link to get the recommendations for YOUR car, truck or SUV. Just add the recommended products to the shopping cart and have then shipped to your home in 2 days. CLICK HERE

AMSOIL OE Synthetic Motor Oil may be used for the drain interval given in vehicle ownersmanuals.

Use this link to get the recommendations for YOUR car, truck or SUV. Just add the recommended products to the shopping cart and have then shipped to your home in 2 days. CLICK HERE

AMSOIL Ea Oil Filters designated with product  code EaO may be used for 25,000 miles or one year, whichever comes first, while those designated with product code Ea15K may be used for 15,000 miles or one year, whichever comes first.

Use this link to get the recommendations for YOUR car, truck or SUV. Just add the recommended products to the shopping cart and have then shipped to your home in 2 days. CLICK HERE

AMSOIL EaAir Filters should be cleaned every 25,000 miles or one year (whichever comes first) up to 100,000 miles or four years.

Use this link to get the recommendations for YOUR car, truck or SUV. Just add the recommended products to the shopping cart and have then shipped to your home in 2 days. CLICK HERE

When to change your oil can save you money, time and wear.

Conventional motor oil companies recommend 3,000-mile drain intervals Conventional 5W-30 Motor Oil* (40 quarts needed for 25,000 miles) @ 3.75/qt. x 40 = $150.00 8 Standard Oil Filters @ 6.00 per filter x 8 = $48.00

TOTAL $198.00

AMSOIL recommends 25,000-mile/one-year drain intervals using AMSOIL Signature Series 5W-30 Synthetic Motor Oil * (5 quarts needed for 25,000 miles) @ 10.15/qt. x 5 = $50.75 1 AMSOIL EaO Filter $18.30

TOTAL $69.05

* Comparison based on 25,000 miles driven per year and 5-quart oil capacity.

You save $128.95 per year using AMSOIL Signature Series Synthetic Motor Oil and on Ea Oil Filter.

Even if you drive only 12,000 miles per year, the cost for AMSOIL is less than you pay for petroleum oil now. All of these benefits add up to an engine that potentially will last longer and need fewer repairs. Change your oil and filter today and in 12 months change the oil and filter again. That’s it! What could be more convenient and good for your vehicle, too? In addition, $10.15 per quart of AMSOIL Signature Series 5W-30 Synthetic Motor Oil is the suggested retail price. AMSOIL Dealers and Preferred Customers pay wholesale, only $7.44 per quart.

Extended oil changes do not void warranties. A warranty remains in force for a period designated by time or mileage, period. If a warranty claim is made during that period, a member of the dealership service staff or a representative of the manufacturer will examine the affected part and make a determination as to the cause of malfunction or failure. If the malfunction or failure cannot be directly attributed to the practice of extended oil drain intervals, then the practice of extending drain intervals cannot be found responsible for the warranty claim and has no bearing on the claim. To date, the use of AMSOIL products in extended service use as recommended by AMSOIL has not been an issue. The point is, AMSOIL products are made to last and the quality engineering that goes into these products proves beneficial whether they are used for conventional or extended drain intervals. All you need to do is be educated about the safety of extended drain intervals with AMSOIL products.

AMSOIL has a documented history of innovation and leadership. In 1972, AMSOIL introduced the first American Petroleum Institute rated 100% synthetic motor oil for automotive applications. AMS OIL was the first to introduce a concept of "extended drain intervals" with a recommended 25,000-mile / 12-month drain interval.

 AMSOIL lubricant technology has been field tested over the last 35 years in the most severe driving conditions. Including family fleets, over the road big rigs, towing, hauling and of course racing. Best Synthetic Motor Oil, Filter, Grease, Diesel Oil. Amsoil Synthetic Motor Oil vs Mobil 1 One Shell Havoline Castrol Pennzoil Valvoline Kendall. Compare 

The lookup guide links below will return the recommended AMSOIL products (oils, filters and plugs) for your specific application.

Simply add the products to the shopping cart from the recommended products list for your vehicle.

Auto and Light Truck lookup Guide

PowerSports Lookup -ATV'S Motorcycles Watercraft and more.

AMSOIL Recommended Oils For Harley Davidson

AMSOIL products (oils, filters and plugs) for your small engine application.

Amsoil By Pass Oil Filter System Application Guide

Heavy Duty Truck, Bus, and Industrial Filter Lookup Guide

****Product recommendations and Drain IntervalsChartPDF

DISCLAIMER & TECHNICAL CONCERNS

Specifications contained on this website are based on manufacturers' information and were believed accurate at the time of publication. Our recommendations apply to AMSOIL products only, as we cannot be responsible for products from other manufacturers. Always compare fluids and lubricants that were installed in the vehicle with those replacing them during service. Never install more fluid or lubricant than what is considered adequate according to gradients on dipstick or level of filler hole. Fill and drain locations are for reference only. Failure to perform adequate inspections or obtain proper resolution will limit or negate any liability toward AMSOIL, Inc.
Models introduced midyear may not have the same specifications as those produced earlier.

If any discrepancies are noted, they can be simply reported to AMSOIL by clicking on the "Report Discrepancies" button found on the top of each application page. All discrepancies are reviewed and if you would like a response, please indicate so by placing your email address in the box provided on the form.

click button

Watch the Amsoil Founder A.J Amatuzio Video

 Watch the 3 Part Amsoil Company/Product Video

 Listen to "Bobby Unser", Race car legend, speak about using Amsoil