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 good rule of thumb for changing piston engine oil is to change it every four months. Of course for every rule, there are at least two exceptions.

Exception #1: If you're able to fly frequently with proper oil temperature, you should adjust the four-month rule accordingly.  Change out your oil after 50 hours if you've flown the hours in less than four months.  If your engine doesn’t have an oil filter, change it after 25 hours. Always remember: the four-month rule is the most critical.

Exception #2: In recent years, the annual flight hours of many private planes have decreased.

And where there’s an idle plane, there’s rust.  When an airplane engine sits too long (especially in humid climates or if there is excess moisture in the oil because the oil temperature is too low), rust will form on many of the parts such as cams, lifters and cylinders. Then, once the plane has been started, the iron oxide will run through the entire engine oil system. 

While some of the larger pieces will filter out, many of the smaller pieces will remain in the oil and can act as grit on critical wear surfaces. If you don't plan on flying your aircraft for four months or more, be sure to use a storage or preservative oil to protect your engine.

D A M anti-seize works on the principle of very small particles of inert dry lubricants imbedding themselves into the open pores of the stainless steel. The dry lubricants lowers friction and prevent corrosive adhesion of the two stainless steel surfaces. The dry lubricants prevent combustion by products from actually gripping the stainless steel. Other products rely on powdered metal such as copper or nickel in a mix of greases and graphite. The powdered metals themselves are often corrosive to the stainless steel at high temperatures and actually create adhesion by microscopic corrosive residue. The old failed theory is that the metal powder flakes will separate from each other and allow disassembly. This does not work at high temperatures and with stainless steel.  Any graphite in the compound (graphite is required for MIL SPEC anti-seize compounds) sets up a severe galvanic corrosion action with the stainless steel and the powdered metals that produces corrosive by products that swell and lock the joint while attacking the grain structure of the stainless steel. This corrosive action is accelerated at high temperatures and contact with combustion by products.    

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.

Baffles and seals are critical to keeping an engine cool, yet they’re often overlooked.  When you’re flying, air enters the cowling and creates static pressure above the engine. This pressure then forces cool air down through your cylinders and oil cooler to the lower pressure areas below and behind the engine. From there, the air travels out through the flaps or other flaring openings. 

What’s important to consider is that there is only a given amount of air coming in through the cowling at any given time. If your baffles are broken or misshaped, the amount of air going past a particular cylinder or area will increase. And if you increase airflow in one area, then airflow past other cylinders and the oil cooler will decrease, leading to higher temperatures in some parts of the engine than others.

Seals can create similar problems. If your seals aren’t in good condition or aren’t properly adjusted, they’ll allow air to bleed out.  Which can reduce static pressure and cooling. So what can you do? Whenever you install a new engine, always have the baffles checked. Also, as part of your periodic inspections, check all the seals for fit and condition. 

If the seals aren’t soft and pliable, replace them. Do this if your oil or cylinder temperatures seem abnormally high as well. Also check how the seals fit against the cowling. If there are noticeable gaps, adjust the seals to reduce air leakage. Be sure to inspect the holes at the rear of the cowling for excessive leakage. If your cylinder heads still run hot, it may be necessary for you or your mechanic to check the static air pressure above the engine during flight. The spec should be available from your airframe manufacturer.

D A M’s light petroleum carrier uses capillary action to penetrate the joint and carry the small particles of dry lubricant into the joint.  By mixing D A M and other solvents such as acetone, MEK or other solvents the viscosity is lowered more yet and the mixture will penetrate small spaces more effectively to loosen corrosion and combustion by products while lubricating the joint.

The polymers and carnauba wax in D A M window cleaner lubricate and encapsulate the abrasive dust and dirt particles so they slide on the plastic surface until they are absorbed deep into the wipe-off towel. The dust and dirt particles are still there, but they cannot get a damaging grip on the plastic surface. After the D A M cleaner is polished off it leaves a protective film that also helps prevent abrasion penetration of dust and dirt particles.

Never wipe a plastic surface when it is dry (or extensively while wet with just water) as some of the abrasive particles will be gouged into the surface, causing scratches.

Placing a permanent reference mark at 180°F on the green band of your oil gauge is a good way to get accurate readings.  To do this, simply place your sending unit and an accurate, referenced thermometer in a steel container filled with oil, and slowly heat it to 180°F with a hot plate. You may not be able to hold 180°F constant, so first mark your gauge with a pencil as the oil temperature passes 180°F. Then let the oil cool back to 180°F. Repeat the process to ensure accuracy. 

And be extra careful with the hot oil. In a naturally aspirated aircraft engine, a cruise oil temperature significantly below 170°-180°F will not ensure that the moisture in the oil is boiled off, especially during short flights. As oil goes through the engine, the highest instantaneous temperature will be about 50°F higher than the oil sump temperature. 

So, if you have an oil temperature of only 150°-160°F, the oil will not get above the 212°F necessary to boil off the water that can accumulate from condensation. The result is increased moisture and acid buildup in the crankcase, which will probably lead to rust and corrosion. 

Knowing this is especially critical if your aircraft is not flown regularly and sits in a humid climate for weeks at a time. If your oil runs well below the 180°F mark, have your mechanic check your oil cooler system and vernatherm. Also, ask about a winterization kit. 

Conversely, the concern with the typical turbocharged piston engine is excessive heat. In many of these engines, instantaneous oil temperature can increase 70°F or more at its hottest point versus sump temperature.  These high temperatures can cause deposit buildup and increased wear due to improperly cooled components or low oil viscosity. (All oils, especially single grade oils, thin out as the temperature

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

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.

No. The pilot or mechanic should always review the manual for proper procedures. For example, on most engines an inspection of the oil pan's suction screen is recommended at each oil change. Although one may rarely find anything during a maintenance check, it's not worth taking the risk.

No, D A M does not have any ammonia or other strong chemicals that could attack or shorten the life of any plastic. D A M has a very small amount of alcohol (less than .3%) in a water based solution. The quantity is so small that it has no effect on plastic or other surfaces. D A M is safe on all surfaces.

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.

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 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.

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 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.

The D A M high temperature anti-seize formula is based on inert high temperature dry lubricants suspended in a naptha carrier with a few other low viscosity additives. The thick grease base in other anti-seize products on the market burn and char at exhaust temperatures leaving sticky hard deposits that actually contribute to the lock-up of exhaust joints. The D A M product carrier evaporates leaving only a film of dry lubricants in the joints that penetrates the pores of the stainless steel.