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G100UL and Engine Oil

PilotjohnS

Well Known Member
Now that the G100UL is a reality, what engine oil can we use?

Can we use a Mobil 1 type synthetic?

Will the synthetic oil and fuel play nice when using the G100UL fuel?
 
From General Aviation News:

https://generalaviationnews.com/202...l-approved-for-all-general-aviation-aircraft/

"Other than being lead-free are there other benefits to G100UL? Spark plug maintenance and replacement intervals will improve with the absence of lead, while it is likely that over time oil change intervals will double. Without lead, it is also likely that synthetic oil will become available that will further increase oil change intervals, GAMI officials said."


Good summary of answers to other questions also.
 
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Now that the G100UL is a reality, what engine oil can we use?

Can we use a Mobil 1 type synthetic?

Will the synthetic oil and fuel play nice when using the G100UL fuel?

Does the manufacturer of the $40,000 USD engine recommend it? IF they do not recommend it, are you willing to experiment with a $40,000 engine by using something that is not an approved oil?
 
Wow this is great news. My god it took them a long time to finally approve this, but still a huge victory for the future of GA!
 
Does the manufacturer of the $40,000 USD engine recommend it? IF they do not recommend it, are you willing to experiment with a $40,000 engine by using something that is not an approved oil?

I am sure Lycoming will be as quick to embrace and approve changes in engine operations and maintenance as they have been in the past.

My guess is that if current published procedures do not hurt the engine they will not changed their published procedures.
 
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Now that the G100UL is a reality, what engine oil can we use?

Can we use a Mobil 1 type synthetic?

Will the synthetic oil and fuel play nice when using the G100UL fuel?

While the the lead debris will go away, these engines still have a lot of blowby and therefore still LOTs of carbon debris in the oil. I would NOT move away from AD oil due to the high debris load that our engines see. Drain intervals are, in part, based upon debris load and debris load has more to do with blowby levels than debris type, I do agree that drain intervals can probably be stretched a bit with UL, but not to the level seen in modern autos. Very different blowby profiles.

Carbon is black and lead is grey. The fact that your oil turns very black over time would seem to support the notion that it is carrying far more carbon debris than lead debris. Highly unlikely that Lyc will change the drain interval spec, as it would be a lot of work to determine how the debris load changes between LL vs UL usage. Best bet is to have someone like Blackstone do a material load test for comparison. In aviation, I believe that the intervals are set based upon when the mfr thinks that the debris load will reach the oil's capacity to hold it in suspension in the worst case scenario. Other factors more related to oil break down times don't really apply to us as the oil loads up with debris to the saturation point long before it starts breaking down.

Also, if an engine sees a steady diet of conventional oil for many years, a switch to synthetic is likely to produce numerous small leaks and should be avoided. Blends are ok. Something about the conv oils swelling or conditioning rubber seals. Once this conv oil disappears, the seals shrink and create the leaks. If the engine always gets synthetic, the problem is not seen.
 
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I’m not a full fan of synthetic oils. There’s no better lubricant when present. It’s affinity for sticking to metal doesn’t match conventional oil unless they’ve changed it somewhat recently. For a daily flyer/driver, sure. For an occasion flyer/ driver, I wouldn’t without a pre-oiler especially an OH cam engine. This will probably elicit some contrary remarks probably based on anecdotal experience. Fine, just look at all of the variable before switching to something “better”.
 
in the old days, drain intervals were about detergent content/quality and about shear stability particularly in multi-viscosity oils. Modern catalytic refining and now synthetic oils have a made shear stability a much, much lesser component, but blowby is still a thing in these ancient old engine designs.

Personally, I’m going to choose an oil from the list that Lycoming publishes as recommended and I’m going to meticulously adhere to their drain intervals.
 
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Even if G100UL extends the oil change interval by hours, there’s still the interval by time that I’m not sure is going to change. How many of us are really flying more than 50 hours every 4 months, and thus would benefit from extended hourly change intervals?
 
The attached service letter from Lycoming should answer everyone's questions.

Google will find it on Lycoming's website too
 

Attachments

  • SL270 Extended Maintenance Intervals for Engines Operated on Unleaded Fuels_0.pdf
    67.3 KB · Views: 255
Even if G100UL extends the oil change interval by hours, there’s still the interval by time that I’m not sure is going to change. How many of us are really flying more than 50 hours every 4 months, and thus would benefit from extended hourly change intervals?

I do. However, I change at 25 (as do many others), if it weren’t for the lead I might consider moving to 50 which this fuel may allow on my comfort scale. Lol
 
The attached service letter from Lycoming should answer everyone's questions.

Google will find it on Lycoming's website too

Very illuminating. Thank you for posting this.

I do. However, I change at 25 (as do many others), if it weren’t for the lead I might consider moving to 50 which this fuel may allow on my comfort scale. Lol

Agree completely.
 
Thanks for the link to the Lycoming SB.

I run on unleaded when I can, but unless I want to stay very local, I'm going to need to burn 100LL. It's quite a challenge to find unleaded when traveling. This is probably going to be the case for a few more years under the best scenarios.

It will be great when leaded fuel is a thing of the past, for all the good reasons that the experts, this time including Lycoming (!), have been saying for a while.
 
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