Which Oil To Use With One New Cylinder

[rockydoc]

I've been using Phillips 20W-50W oil in my bird.

Recently, changed one cylinder for a new one.

The mechanic put in 100W.

What is the best oil for me to use now with only one new cylinder?

[aaronk25]

Whatever oil you use dump it after 3-5 hours as the rings let a lot of blowby past and pollute the oil and the blowby partials are highly pro-wear and you have other things that don't need "breaking in" specifically the cam and lifters.

This is straight from Ed at cam guard......

Leave the filter on, you don't have to change it....just dump the oil.

[Guest]

You should be following Lycoming SI 1427C for cylinder break in procedures and SI 1014M for correct oil.

Clarence

[rockydoc]

This is straight from Ed at cam guard......

Leave the filter on, you don't have to change it....just dump the oil.

Thanks.  Which oil should I use?

[aaronk25]

So as M20doc pointed out the service instruction from Lycoming says non-turbo birds should use Mineral oil and turbo should use a anti-dispersant oil (regular aviation oil).

It's really up to you....and I don't think you would go wrong either way. I can't remember if your running a turbo or not.

Assuming you don't have a turbo, the problem with mineral oil is it doesn't disperse the blow by wear partials as it's designed to let the engine "break in", but your cam and lifters, which are under extreme pressure and operate close to the design tolerances, as evident by how many failures we see, don't need "wearing in", again.

Id say keep running the oil you have but run at 75% for the first few hours (assuming it's a basic steel cylinder you are putting on) and pay special attention to keep temps under 380 so as not to damage the rings.

If the mechanic fills the engine with mineral oil go fly it for a hour or 2 and when you get back to your hanger pull the quick drain, dump the oil and refill with your regular oil.

Ed at Camguard and me had a long discussion about why so many planes that get a new cylinder(s) have cam/lifter failure after just a few hundred hours. He is convinced that the hot gasses blowing by unseated rings on new cylinders bathe the cam and lifter with pro wear particles combined with not changing oil soon enough during break in is responsible for the early demise.

Just my thoughts, from actual experience....

[rockydoc]

So as M20doc pointed out the service instruction from Lycoming says non-turbo birds should use Mineral oil and turbo should use a anti-dispersant oil (regular aviation oil).

It's really up to you....and I don't think you would go wrong either way. I can't remember if your running a turbo or not.

Assuming you don't have a turbo, the problem with mineral oil is it doesn't disperse the blow by wear partials as it's designed to let the engine "break in", but your cam and lifters, which are under extreme pressure and operate close to the design tolerances, as evident by how many failures we see, don't need "wearing in", again.

Id say keep running the oil you have but run at 75% for the first few hours (assuming it's a basic steel cylinder you are putting on) and pay special attention to keep temps under 380 so as not to damage the rings.

If the mechanic fills the engine with mineral oil go fly it for a hour or 2 and when you get back to your hanger pull the quick drain, dump the oil and refill with your regular oil.

Ed at Camguard and me had a long discussion about why so many planes that get a new cylinder(s) have cam/lifter failure after just a few hundred hours. He is convinced that the hot gasses blowing by unseated rings on new cylinders bathe the cam and lifter with pro wear particles combined with not changing oil soon enough during break in is responsible for the early demise.

Just my thoughts, from actual experience....

thanks for going into so much detail.  That gives me the exact information I needed.  So, I'll drain the mineral oil after 3-5 hours and continue using Phillips 20W-50 as before the cylinder replacement.

Happy flying,

Rocky

[jetdriven]

Lycoming says mineral oil but many overhaulers say that Philips 20w50 is ok too.