[mfshook62]

I have a few general questions about aviation oil:

1. My engine was rebuilt in 1996 at Lycoming and now has about 1400 hours. I have been wondering for some time about the 50 hours between oil changes that Lycoming recommends. Is there any data that says you must change the oil and filter at 50 hours or your engine will seize up, or is it just a Lycoming-Aeroshell agreement to be very conservative and increase profits by selling all of us $36 of oil every 50 hours, when they probably know that we could go longer than that between changes. My last oil analysis from Blackstone showed everything normal and nothing out of range. Is there any recorded correlation between oil age and engine damage? Usually at 50 hours I have already added about 3+ quarts, so the majority of the oil only has about 10-25 hours of use. Does this mean that I can go a few more hours? I know that its not a large expense in the realm of aircraft costs, but is it really necessary? What is the consensus about time between changes?

2. My petroleum vendor has many varieties of aircraft oil ranging from $40-75 per case. I use the expensive oil, Aeroshell 15W-50, which is a multi-grade semi-synthetic oil. The less expensive oil was single grade and non-synthetic. I live in a warm climate, do I need multi-grade or synthetic oil? Who is using the $40 a case oil and have you ever had problems using it?

 

[RV6_flyer]

Talking about oil is very similar to talking about primer. There are many opinions.

We use 100 LL fuel in our aircraft engines. The LOW LEAD is not low lead but is lower than it use to be years ago. Lead does build up in the oil as a sludge and thus the oil change is needed.

Fact: None of us NEED multi-weight oil.
Fact: Multi-Weight oil is THICKER because of the additive package at elevated temperatures than is a single weight oil.


I have a constant speed prop. Using the multi-weight oil, I am ready for takeoff at 70 F oil temp. If I use a straight weight oil, I need to wait till I have 100 F oil temp. Lycoming says that you can take off when you can advance the throttle and the engine RPM increases normally. The constant speed prop cycles smoothly is something that I added. I prefer and use the multi-weight oil because of this.

I have used AeroShell 15-50 most of my engine life. I use Phillips 20-50M for break-in an then use Phillips X/C 20-50 for the next 100 hours or so. The only reason that I am going back to AeroShell 15-50 is because it contains the Lycoming LW 16702 antiwear additive that protects the engine better. It is NOT REQUIRED on in my engine but it is required in some of the Lycoming engines. If I purchase the less expensive Phillips X/C 20-50 and add the LW 16702 additive to the oil, I end up spending the same amount of money. It would be an extra step to purchase the LW 16702 additive and add it at every oil change.

I flew my airplane over 2,200 hours before doing a top replacement. The bores of the old cylinders still had the hone cross-hatch and measured out at NEW spec including the tapper. The valve guides were wore out.

At the present time, I will be down one quart of oil at 45 hours after oil change. I do not add a quart but just change the oil instead of waiting 5 hours and then doing the change.

Hope this helps. You will be getting a lot of other opinions.

 

[AK4x4]

Oil change

Lycoming recomends that you change your oil every 50 hrs ... or 4 months which ever occures first assuming you have a filter. Its 25 hrs for engines with screens. The reason for this has nothing to do with the oil "wearing out" the oil is fine. Dirt is the problem. Carbon (soot), lead byproducts, acidic combustion byproducts, ect (dirt) all build up in your oil and form a fluid abrasive which is circulated around the engine with the oil. This is removed when you change the oil. With better filtration the change interval is extened hence the 25 and 50 hour numbers. In theory if you installed a remote high efficancy filtration system similar to Amsoil's system you could increase the time between changes due to superior dirt removal. HOWEVER, the other issue is anti corrision additives. Acid is a cumbustion byproduct. Their are anti corrision additives in your oil both to netralize the combustion byproducts and to retard corrosion (rust) when your engine is not running. These additives get used up with time, hence the "or 4 months". The time of highest acid exposure is when the engine is cold. When the oil is hot the acid is boiled off and goes out the breather/exhaust as a vapor. Hence engines that fly all day long (135 operators) live a long time and engines that dont (mine and probably yours) have shorter lives.....and a greater need to have the oil changed. As far as what oil to use, W100 and 15W50 are the same thickness at normal operating temp the differance is at cold temps the 15W50 will flow nicely but the W100 will not. So if you operate under varing temps like we do in Alaska I recomend 15W50 however if you hangar your aircraft or operate were it is above 50 degrees save your money and run W100plus. What is W100 plus? simple it is W100 with the Lycoming antiwear additive. Good Luck, Russ