I don't understand why the exhaust on my 350is continues to be black and sooty. Was like that when I uncrated it and hasn't improved after 10 hours of operation.

Views: 290

Reply to This

Replies to This Discussion


Break in period of an engine is complete when the rings seat. You can tell when the rings seat by when the engine stops using oil. On a UL that should be around 10 hours. Until then you will be blowing oil past the rings and out the exhaust. Use the recommended oil and watch your oil level. Your rate of consumption will slow and then drop to an ounce every couple of hours. 

Enjoy flying!



I had the same problem with my 260i until I took a trip to high desert Oregon for the full solar eclipse.  After the engine was run hard and hot the black went away and my oil consumption went to almost 0.  Don't be too easy breaking in your engine or the rings will never seat properly.  My A/I is in total agreement with this, run it hard and hot.     Cheers,,,,,,,,,,,,, Lynn N984LD

OK,  thanks guys. Will be running it hard now that it's flying and looking for improvement. 

You might check out a blog myULpower.com.  The article is ‘ Fix the mix’. I’m planning on doing the mod.

Thanks Greg.  Yet another mod to put on my to do list.


New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Golden Eagle Aviation

Pianosa Flying Farm

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2021   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service