Straight Weight Mineral Oil in Lycoming?

[3Dreaming]

Re: Straight Weight Mineral Oil in Lycoming?

Tom,

So you recommend the straight weight mineral oil for Chris?

Marty,

It has been 20+ years, I don't remember what I ran in it. I would have to look at the records to make the decision on what oil to use.

[M Towsley]

Re: Straight Weight Mineral Oil in Lycoming?

Tom,

So you recommend the straight weight mineral oil for Chris?

[3Dreaming]

Re: Straight Weight Mineral Oil in Lycoming?

The engine is a 0-145 Lycoming. It has about 200 hours since major overhaul in the early 1990's. The Cylinders are cast iron and part of the crankcase. The recommendation for the straight weight mineral oil came from the engine type certificate holder.

[Mark Bowden]

Re: Straight Weight Mineral Oil in Lycoming?

I put the following in the ref section. Always go to Continental's site for the current version to maintain compliance. It defines engine lubricants.

SIL99-2C is Continentals Service Information Letter on

SUBJECT: SEALANTS, LUBRICANTS, AND ADHESIVES AUTHORIZED BY CMI

PURPOSE: Provide current application of sealants, threading, lubricants, and adhesives.

COMPLIANCE: During engine installation, maintenance, overhaul or component repair or replacement.

MODELS AFFECTED: All CMI engine models operating with AVGAS (gasoline based) fuel.

I'm sure there is a Lycoming equivalent but I don't have it. Maybe someone else has access to it or Lycoming's support site.

It is nice because it identifies all approved materials for lubes, gaskets, sealants, etc...


Hope it helps, Mark

[Mark Bowden]

Re: Straight Weight Mineral Oil in Lycoming?

First question to ask is how far from SMOH or cylinder replacement? Why? The manufacturer or overhaul shop may have requirements so you do not void their warranty.

The quoted individual is in error. Aviation oils do NOT contain detergents. Detergents have metallics in them, do not use them.

Sludge is NOT acceptable in an engine.

Aviation oils are from mineral oil base stock. Mineral oils do NOT have “abrasives” in it. Straight weight oils do not contain AD’s (ashless dispersants), they are not multi viscosity oils.

AD, mutli-viscosity, oils come from the same base stock as straight weight oils. The AD additive package is there to collect and suspend dirt and combustion products to prevent those contaminants from collecting in the engine causing sludge build ups. The additive package transports them to the paper filter for removal or removal when you change your oil.

That’s why it is so dirty. If you wait too long between changes the additive package is all used up and then it behaves like the straight weight mineral oil. It cannot suspend the additional combustion contaminants that keep coming from continued use. The multi viscosity still works.

Think of the additive package like Velcro for carbon and dirt. It grabs ahold of it and hangs on. However their only so much available and then it is “full” and can’t grab any more.

Full synthetic oils come from different base stock and they are not recommend in air-cooled aircraft engines. Automotive use only.

AD oils are not “more slippery” straight weight oil, break-in can be accomplished on either oil type. However, follow the OEM manual or the overhaul shops requirements to preserve your warranty.

How you run you engine is most important for proper break-in than oil type. The requirement for straight mineral oil is an old one that has been codified in the OEM manuals regardless of changes in technology or evidence to the contrary. Lycoming documents require both straight and multi-viscosity, AD oils depending on engine model for break-in hours.

If all you have is a screen in the oil system and not a paper filter, AD, mulit-viscosity is going to be hard to beat. In addition to retaining viscosity and film strength at high temperatures.

Biggest impact on oil and engine health, run it properly then change it often, sooner more so than after 25 hrs.

[M Towsley]

I am posting this question for Chris Kappler who recently bought the Baker's Lycoming-powered pre-war. He is still having difficulties getting onto the forum. See the question below.

Hackenburg said I should run straight weight mineral oil in that engine. Something about the Lycoming having seven sludge tubes and I didn't need the detergents in the modern oils and mineral oil was better. It was hard to follow what he was saying but, in the end, it almost seemed like he was saying I didn't "need" the modern, fancy detergents but other than that, it didn't matter what I ran as long as it was straight-weight. I don't want to run anything wrong in there but I'm afraid mineral oil has abrasives in it that might not be good long-term. I'd like some opinions if possible. Thank you.