Yes. AeroShell straight mineral oils meet the SAE J-1966 former MIL-L-6082 specification.  AeroShell Oil W single grade and antiwear, anticorrosion AeroShell Oil W 15W-50 meet the SAE J-1899 former MIL-L-22851 specification. The AeroShell containers are labelled with both the new SAE specifications and the “former” military specifications.

The compatibility question covers two issues: mixing one grade of AeroShell oil with another; and the effects on the engine of changing from one AeroShell grade to the other. If you typically run on AeroShell multigrade, and you find yourself in a place where only AeroShell single grades are available, you can safely add the AeroShell single grade to your engine. They are completely compatible. 

If you run on an AeroShell single grade during the summer, but want to switch over to AeroShell Oil W 15W-50 Multigrade for the winter, you can safely replace the straight weight with the multigrade at your regular drain interval. The idea that you have to stick with the type of oil you started with comes from the days of unusual chemistry when the resulting oils were incompatible. 

All approved SAE J-1899 (former MIL-L-22851) and SAE J-1966 (former MIL-L-6082) AeroShell oils are compatible. For example, if you have a high-time engine run on ashless dispersant oils and need to replace a cylinder, you can switch to a mineral oil for 50 hours or so to break in the new cylinder. The only time Shell recommends against switching is in a high-time engine run exclusively on straight mineral oil. Here, a switch to ashless dispersant oil can loosen deposits left behind by the mineral oil.

Both Lycoming and Continental recommend oils qualified under the following specifications for use in their engines:

• SAE J-1899 former MIL-L-22851 (for ashless dispersant oils)
• SAE J-1966 former MIL-L-6082 (for straight mineral oils, intended primarily for break-in)

Military and SAE specifications are the same except for some additional packaging requirements for the military. In the future, the military specification may be dropped, although oil containers will still probably refer to the former military specification.

AeroShell® straight mineral oils, AeroShell Oil W single grades and AeroShell Oil W multigrade oils all qualify under their respective specifications. The oil requirements for other aircraft engines such as Pratt & Whitney are less defined. All AeroShell and AeroShell Oil W oils are qualified for use in P&W radial piston engines. The oils for engines no longer in production may be listed by military specification or by product name.

For more information, talk to an overhaul or repair shop that specializes in a particular engine, or call the Shell Technical Information Center at 1-800-231-6950.

The selection of a proper grease is clearly defined. For each grease point on a certified aircraft, the military specification or the qualified product is listed. AeroShell® greases are qualified under the following specifications:

• AeroShell GREASE 5 former MIL-G-3545-C
• AeroShell GREASE 6 MIL-G-24139A, former MIL-G-7711A AeroShell GREASE 7 MIL-PRF-23827C, TYPE II
• AeroShell GREASE 14 MIL-G-25537C
• AeroShell GREASE 16 former MIL-G-25760A, BMS-3-24A AeroShell GREASE 17 MIL-G-21164D
• AeroShell GREASE 22 MIL-PRF-81322F, Grade 2 DOD-G-24508A AeroShell GREASE 33 MIL-PRF-23827, TYPE I BMS-3-33A

The oils are similar, but there are some differences. The biggest difference is in cold flow characteristics. AeroShell Oil W 100 is up to 10 times thicker at cold temperatures than AeroShell Oil W 15W-50.  However, at normal operating temperatures (around 200°F), both oils will have the same thickness or viscosity.  Another major difference is that AeroShell Oil W 15W-50 and AeroShell Oil W 100 Plus have an antiwear additive which is not in AeroShell Oil W 100. This additive, along with the semisynthetic base oils, helps reduce friction and improve flow in AeroShell Oil W 15W-50. 

These additives improve lubrication and reduce oil consumption past the oil rings. Conversely, the improved flow can increase oil loss through leaks or loose intake valve guides.  So your oil consumption may go up or down if you switch from AeroShell Oil W 100 to AeroShell Oil W 15W-50. The improved flow and reduced friction characteristics of AeroShell® Oil W 15W-50 will also help reduce oil temperatures as opposed to using AeroShell Oil W 100. 

This is particularly important in engines that run hot, like turbocharged, high performance or aerobatic aircraft engines. Pilots should always remember to monitor oil temps to ensure that they’re not too hot. 

In cold weather, you should also make sure that the engine temperature is high enough to boil off the water that naturally accumulates in the crankcase. Temperatures in the 180° to 200°F range are recommended for most applications. Finally, if you have a marginal or slipping starter clutch, the antiwear additive in AeroShell Oil W 15W-50 may cause it to slip more than AeroShell Oil W 100.  Understanding these differences can help you select the grade of AeroShell that's right for your plane.

No. Due to the additive technology in ashless dispersant lubricants like AeroShell W Oils, the flow characteristics of each grade are roughly equivalent to the next higher grade straight mineral oil. For example, AeroShell Oil W 100 will flow at low temperatures about the same as AeroShell 80.

No. The W is just a model designator to differentiate between AeroShell ashless dispersant oils (Oil W) and straight mineral AeroShell oils which have no letter designator.

All AeroShell oils are compatible and can be mixed with each other. Many single grade customers try AeroShell Oil W 15W-50 during the colder part of the year, then convert to using it year round. Others, however, choose to alternate between single grade and multigrade depending on the time of year. Either system works well because AeroShell oils are entirely compatible and can be interchanged as desired. 

In addition, if you need to replace a cylinder on a mid-time engine, you can switch from AeroShell Oil W single grade or AeroShell Oil W 15W-50 to a straight AeroShell mineral oil for one or two changes to break in the new cylinder. Then you can switch back to the ashless dispersant oil after the rings are properly seated. 

If you have a mid-time engine that has been run exclusively on a straight mineral oil and wish to try an ashless dispersant oil, use caution. The introduction of an ashless dispersant oil into your engine could loosen up some of the carbon deposits. So check your oil screens and filters often to ensure against oil starvation and/or oil screen collapse.

The old adage that one should never change oil types was based on problems with some oils with very “unusual” technology that were in the marketplace over 50 years ago. Present oils are compatible. So many pilots use AeroShell Oil W 15W-50 multigrade in the winter months and then switch to AeroShell Oil W 100 or AeroShell Oil W 100 PLUS single grade in the summer months. You may see small changes in oil temperature or oil consumption with this change, but it will not hurt your engine.

A number of pilots have asked this question. The answer is a definite no. When Shell first started evaluating multigrade aviation piston-engine oils over 25 years ago, testing proved that multigrades formulated only with mineral base oils did not have adequate base oil viscosity (thickness) to properly lubricate all high load points in the engine. Then we tested and flight evaluated a formulation made with all-synthetic base oils.

This formulation had excellent antiwear characteristics in all tests run. However, in the flight evaluations, some engines would reach 600 to 900 hours, then lose oil consumption control and/or compression. When the engines were disassembled, we found that the piston rings were covered with a gray tacky substance that was primarily made up of the lead by-products of combustion (from the use of leaded aviation gasoline).

Although synthetics are excellent lubricants with good high temperature stability and very good low temperature flow characteristics, they are relatively poor solvents.

In an aircraft engine, the lead by-products of combustion must be dissolved by the base oil so they can be carried away from the ring belt area and removed from the engine when the oil is changed. Anticorrosion, antiwear AeroShell Oil W 15W-50 is formulated with 50% synthetic base oils to give it the excellent low temperature flow needed for quick lubrication during cold starting. 

The synthetic base oils, along with the unique antiwear additive system, give it antiwear protection unequaled by any other product on the market. In addition, its mineral base oils provide lead absorbency to guard against ring sticking and excessive sludge. The bottom line: The synthetic component of AeroShell Oil W 15W-50 will not harm your engine. Instead, it gives you the best of both oils.

Over the years, a number of oils have come and gone. Most new products perform great in one bench test or another, or even in a short-term engine test. But loboratory conditions may not duplicate real world conditions. The best way to judge an oil is to see how it performs in actual service, under real world conditions. 

Some of these conditions may include sitting for weeks at a time, starting in less than ideal conditions, and flying on days that your mother would have told you to stay home. Oils with a proven track record, like AeroShell oils, can be counted on to deliver top performance year after year.

Yes, low oil temperature can lead to excessive rusting and corrosion of critical engine parts. When an aircraft sits on the ramp or in a hangar, the engine heats up during the day and cools again at night. While the engine is cooling, some of the moisture in the air condenses on the engine walls and drops into the oil. 

This can form rust on internal engine components. The moisture can also react with by-products of combustion in the oil,forming acids which can lead to corrosion. The best way to remove this water is for the engine to boil it off during flight. Studies have shown that the temperature of your engine oil increases about 50°F as it circulates through the engine.

Therefore, unless the oil temperature reaches 170°F to 180°F during flight, the engine will not boil off the water that has accumulated in the crankcase. The result: rust and corrosion.

Note that an excessively high oil temperature will also cause problems. Here are some tips to help avoid oil temperature problems:

Check your oil temperature gauge for accuracy. It should read about 212°F when the sensor is placed in boiling water.

Monitor the oil temperature during flight. It should be about 180°F even in winter. If it is lower, you may need a winterization kit. Otherwise, check with your mechanic to see what is causing the excessively low oil temperature.

The unique additive feature in anticorrosion/antiwear AeroShell® Oil W 15W-50 can also help control problems caused by rust and corrosion.

Preheating your engine makes a world of difference. This procedure heats the oil so it’s thin enough to flow through the engine and properly lubricate all critical wear surfaces.  Preheating also heats the metal parts in the engine. That’s important because aluminum crankcases have a higher coefficient of thermal expansion than iron crankshafts. 

This means as your engine cools down, the clearance is reduced.  And as a result, you may not have sufficient oil film thickness for proper hydrodynamic lubrication at very cold temperatures. In other words, the wear rate is going up. 

One final note of caution on heaters: Do not plug in a heater and leave it on for extended periods of time. If you have moisture in your oil, the heater will increase vaporization, which will condense on the cool, nonheated engine parts and increase rusting.

Airplane air/oil separators are also worthy of discussion. Separators are designed to remove the oil from the blow-by gas and return it to the crankcase. This reduces oil consumption and keeps the belly of the airplane clean. Properly installed, separators work well. 

However, if the system is installed with parts in a cool area under the engine cowling, it can condense all of the water evaporated from the oil and return it to the crankcase. 

If you have a separator, make sure it’s properly installed with the exit tube in a low pressure area which will evacuate the water vapor and not force it back into the crankcase. While preheating and the proper air/oil separator are essential to long engine life, they are no more essential than the oil you use. AeroShell® Oil W 15W-50 offers unsurpassed anticorrosion and antiwear protection for all kinds.