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Synthetic Diesel Motor Oil FAQs

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I was taught to change my oil every 3,000 miles, and most people I know still follow this rule. If it’s possible to drive farther between oil changes, why do so many people still adhere to the 3,000-mile rule?

When oil filters were introduced in the early 1920s, many vehicle manufacturers began recommending changing the motor oil every 3,000 miles. Naturally, repair facilities and oil-change shops adhered to this recommendation for the customers they served. As engine and lubrication technology advanced through the later part of the century, vehicle manufacturers began recommending increasingly longer oil-change intervals. Quick lubes and other oil-change facilities, however, continued recommending 3,000-mile drain intervals, perpetuating what is now known as the "3,000-mile myth."

Most vehicle manufacturers today recommend much longer between oil changes, and many feature an on-board oil life monitor that uses driving habits to determine when the vehicle’s oil should be changed. Whether you follow the recommendation in your owner’s manual or choose an AMSOIL synthetic motor oil that lasts even longer, you’re sure to drive more than 3,000 miles between oil changes, and you’re sure to do so without damaging your vehicle’s engine.

Can I use AMSOIL synthetic diesel oil without voiding my vehicle’s warranty?

Yes. Using AMSOIL synthetic diesel oil has no effect on vehicle warranties. A federal law called the Magnuson-Moss Act (1975) prevents original equipment manufacturers from putting conditions on vehicle warranties attached to any product or service identified by brand, trade or corporate name, unless the manufacturer provides that product or service free of charge. This means consumers have the freedom to use aftermarket products of their choice without fear of losing the original limited or implied vehicle warranty. For additional information, visit www.amsoil.com/warrantysecure, or contact the AMSOIL Technical Department at (715) 399-TECH (8324) or tech@amsoil.com.

Will extending oil drain intervals void my vehicle’s warranty?

No. Extending oil change intervals will not void new vehicle warranties. To affect the vehicle warranty, it must be determined that the lubricant was directly responsible for the failure; if the oil didn’t cause the problem, the warranty cannot be voided, regardless of brand or length of time in use. For additional information, visit www.amsoil.com/warrantysecure, or contact the AMSOIL Technical Department at (715) 399-TECH (8324) or tech@amsoil.com.

Does AMSOIL offer diesel oils for equipment calling for the API CJ-4 specification?

Yes. AMSOIL Premium 5W-40 Synthetic Diesel Oil, Premium 15W-40 Synthetic Diesel Oil, OE 15W-40 Synthetic Diesel Oil and OE 10W-30 Synthetic Diesel Oil are recommended for diesel applications calling for the API CJ-4 specification.

Are the AMSOIL CJ-4 diesel oils OK to use in older diesel engines?

Yes. AMSOIL Premium 5W-40 Synthetic Diesel Oil, Premium 15W-40 Synthetic Diesel Oil, OE 15W-40 Synthetic Diesel Oil and OE 10W-30 Synthetic Diesel Oil are formulated with lower sulfur content to be compatible with 2007 and later high-speed, four-stroke diesel engines with exhaust after-treatment systems, and they also exceed previous diesel oil specifications. They are suitable for use in older diesel engines calling for API CI-4 Plus, CI-4, CH-4, CG-4 and CF-4 oils.

What are "normal" and "severe" driving conditions?

Each vehicle manufacturer defines "normal" and "severe" driving conditions for its equipment; AMSOIL recommends owners check these definitions in their owner’s manual to determine the service condition in which they typically drive.

AMSOIL defines normal service as personal vehicles frequently traveling greater than 10 miles (16 km) at a time and not operating under severe service.

AMSOIL defines severe service for gasoline engines as turbo/supercharged engines, commercial or fleet vehicles, excessive idling, first-time use of AMSOIL synthetic motor oil in vehicles with over 100,000 miles without prior continuous use of AMSOIL synthetic motor oil, daily short-trip driving less than 10 miles (16 km), frequent towing, plowing, hauling or dusty-condition driving.

AMSOIL defines severe service for diesel engines as extensive engine idling, daily short-trip driving less than 10 miles (16km) or frequent dusty-condition driving.

See the AMSOIL Product Recommendation and Drain Interval Chart for additional information.

Do I have to use an AMSOIL Ea Oil Filter with AMSOIL synthetic motor oil?

No, you can use whichever brand of filter you choose and AMSOIL synthetic motor oils will still be guaranteed to protect your vehicle for the advertised period. However, you will need to change your oil filter according to the filter manufacturer’s recommendations and top off the oil.

I understand AMSOIL synthetic motor oil resists boiling off in high temperatures. Do I still need to check the oil level in my car between oil changes?

Yes, it is normal for vehicles to use some motor oil. AMSOIL recommends checking your oil level every time you fill your fuel tank.

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