Is there engine (motorcycle?) oil w/ a GL4 or 5 rating?

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I'm looking for an engine oil, that carries a GL4 or 5 rating? If such a thing exists? It's for the engine in my airplane that shares oil with the reduction drive (gearbox).

I emailed AMSOIL and asked if any of their motorcycle oil met that GL rating, and after several emails the rep never would answer the question whether they did, or didn't. All he wanted to know was the application. When I told him it was for an experimental aircraft he told me he wouldn't talk to or help me any further and never responded again. I'm familiar with people getting uneasy when you throw out the aircraft term, but it is experimental and is in a whole different category from certified aircraft. Oh well.

Anyway.. I've done some research and so far I have not been able to find any engine oil with more than a GL1 rating. Rotax worked with Shell to develop a semi-synthetic oil for this application, and it's a good oil, but a high end (group 4 or 5) full synthetic would be better. Apparently full synthetic oil doesn't work well with leaded avgas because it doesn't trap the lead properly. Or at least that is the story. But when I'm not traveling or going to fly-ins with the plane and just out landing on hills and playing (majority of the time) I would like to run a synthetic because I use pump gas most of the time.

The gearbox does get hammered, especially since I installed larger cylinders and 11:1 forged pistons and built he headers, muffler, ram-air etc. to get some more power out of it. I'd really like to find the best quality oil for the application. Rotax actually put out some literature at one point that called for an engine oil with a GL 4 or 5 rating, but I have never been able to find any. I've always felt that Motul and Redline make good oil, along with plenty of other manufactures, but I have no idea on their oils either as far as this goes?

I really do appreciate any help!
 
Why a "motorcycle" oil? You have no wet clutch...and plenty of autos have gears driving oil pumps, camshafts etc. lubed by the crack case oil.

I can't think any crancase oil is going to have a GL rating....and no Gear Lube is going to be good for engine use. I say stick with the Rotax oil.
 
Originally Posted by GravityKnight
Rotax worked with Shell to develop a semi-synthetic oil for this application, and it's a good oil, but a high end (group 4 or 5) full synthetic would be better


OK, so I know a guy with a Rotax 912 from the 1990's - it has about 1800 hours on it, and it's run Napa 10W-40 oil it's whole entire life.

Don't worry about it. Run any good oil - all will be fine.
 
Use motul Ferrari engine oil
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OK, first I'm an A&P and EAA member #1165026. (I need to qualify here that I don't have Rotax experience. My aviation recip experience ranges from P&W R-4360's and IO-360 Continentals. Everything else is jets). Second, since I see this is your first post, Welcome.
welcome2.gif


That's a good looking S-6S you got there Gravity Knight. I'm guessing that a 914 wasn't doable since you're running those mods?? Now for your question. First I don't think that pump gas will provide enough octane for 11:1. I'm real concerned you'll get detonation. How many hours on it since you did the mods? Have you inquired about that from Rotax? That said, I still don't think that even with a FADEC, pump gas has enough octane which leaves you with either racing fuel or 100LL, which actually has a lot of lead and it's fouling issues. As far as oil goes, no GL-4 or 5 oil that I know of will provide the engine protection you need. My recomendation would be Aeroshell Sport +4. It's approved by Rotax. Here's a link: Aeroshell Sport Plus 4 That should be sufficent to address the gearbox issues. But again, I would really see if you could get some idea from Rotax. Hopefully they won't hang up on you when they find out you are running such serious mods. Good Luck!
 
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I would recommend you contact Blackstone Labs because they do a lot of UOAs for aviation applications and would both know about many choices, and be able to tell you if any trends exist for your application.
 
I'm not sure if they still do, but Harley used to state you could use their Syn III motor oil in your Harley's transmission. So did Amsoil and Mobil 1, for their motorcycle oils. I believe they claimed it was equal to having a GL-1 rating. I never used in in my trans, instead I used Gl-5 gear oil because there's no brass in a Harley's trans. Pretty much every metric bike made uses the shared sump concept, and it seems to work for them considering the amount of sport bikes that get hammered on. Unless you have a separate oil fill for your particular trans, I wouldn't be too concerned about it.,,,
 
Originally Posted by ammolab
Why a "motorcycle" oil? You have no wet clutch...and plenty of autos have gears driving oil pumps, camshafts etc. lubed by the crack case oil.

I can't think any crancase oil is going to have a GL rating....and no Gear Lube is going to be good for engine use. I say stick with the Rotax oil.


Lot's of engine oils have a GL-1 rating. Rotax specifically states the engine oil needs a GL 4 or 5 rating. Weird I know, that's why I came here to ask, because I've never seen it before. The gear reduction box driving my 75" propeller gets hammered worse than the gears driving an oil pump or camshaft. Obviously, in most cases, if the oil was seperate, you would want some viscosity of gear lube on those gears, but similar to a motorcycle that shares the engine oil with the transmission, they wanted an oil up to the task of doing both. Now... is regular "non-motorcycle" oil unable to provide protection in these instances, I would guess there are plenty of quality oils that could, but I'm not here making that speculation. I was looking to see if I was nuts when I came to the conclusion that there are no engine oil's that carry a GL 4 or 5 rating.


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What about Honda ATV oil, believe its rated GL 4.

Before shell came out with the sport + 4 oil, I know a lot of folks used to run Honda GN4 oil. I think it was actually on Rotax's recommended oil list before they created their own oil. I never could find any GL rating... do you recall where you got the info about it possibly being GL4? just curious.


Originally Posted by jetmech1
OK, first I'm an A&P and EAA member #1165026. (I need to qualify here that I don't have Rotax experience. My aviation recip experience ranges from P&W R-4360's and IO-360 Continentals. Everything else is jets). Second, since I see this is your first post, Welcome.
welcome2.gif


That's a good looking S-6S you got there Gravity Knight. I'm guessing that a 914 wasn't doable since you're running those mods?? Now for your question. First I don't think that pump gas will provide enough octane for 11:1. I'm real concerned you'll get detonation. How many hours on it since you did the mods? Have you inquired about that from Rotax? That said, I still don't think that even with a FADEC, pump gas has enough octane which leaves you with either racing fuel or 100LL, which actually has a lot of lead and it's fouling issues. As far as oil goes, no GL-4 or 5 oil that I know of will provide the engine protection you need. My recomendation would be Aeroshell Sport +4. It's approved by Rotax. Here's a link: Aeroshell Sport Plus 4 That should be sufficent to address the gearbox issues. But again, I would really see if you could get some idea from Rotax. Hopefully they won't hang up on you when they find out you are running such serious mods. Good Luck!


Thanks for the warm welcome, and all the info. Appreciated! You worked on radials I see.... that's neat!!. Nothing sounds quite like a radial!! I have done a lot of work to my plane over the last 3.5 years, and it has taken me on countless adventures doing things at times so amazing it is hard to put into words! What a great experience it has been!

I started with a 100hp 912, so the best path ($$$) was to work from there. I'd love a 914, but not in this 6 as it's nose heavy to begin with. The upgrades I did with the billet cylinders and forged pistons actually shed 3lbs off the engine. I live at 6600ft, so the 11:1 compression is no problem on pump gas, anytime I travel to somewhere lower, I'm having to run 100LL anyway so that takes care of that. If I was at or near sea level, I would also be quite worried about the compression, although it has been done by others interestingly (terrifyingly?) enough. I have about 940 hours on the engine total - about 440 of those on the high compression top end.

The sport + 4 is definitely good oil. Typically I preheat the engine in the cold times of the year, but from time to time, it has to be started in less than ideal conditions. It would be nice to have a full synthetic oil (proper oil to meet the requirements of the gearbox). I know a couple different guys running Mobil 1 4T 10w40 all the time in theirs, even on leaded avgas!! So far no issues, but a) I'm convinced there are better oils out there than that, and b) from the research I've done, lead and synthetic isn't a good idea. I guess I'm a bit of an oil nerd and am always searching for something 'better' ... which could be an absolute waste of time!!!!

Yea, I have a feeling Rotax wouldn't want to talk to me since I have modified their engine that much. I haven't tried to contact them, but I know a few Rotax certified mechanics and they basically said rotax washes their hands of anything out of the norm. I get that. But flying up to 16k and needing to keep it light and simple for bush flying I did what I had to do to make it perform. There is a company called Edge Performance that builds 155hp+ injected/turbocharged 912's and they have sold a ton of them. So far they are holding up with no issues. Highest motor to date has 1500 or so hours, but they have probably another 25-30 in the 400-500hr range. Neat stuff, I came from the car world and built and tuned many turbo setups - I love the technology. My next plane with have something along these lines. On this one I wanted to keep it simple, light, and affordable, and work up from there. Easing into it so to speak being that it's aviation after all. I like landing in random places... that I choose!!! The next one will be a little more extreme... and of course, sadly, more costly.


I appreciate the replies.
 
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I was looking to see if I was nuts when I came to the conclusion that there are no engine oil's that carry a GL 4 or 5 rating.


A GL-4 or 5 rating is a protection rating for machines with gearing and bearings that need Extreme Pressure (EP) additives.

EP additives contain high levels of sulfur-phosphorus or phosphorus chemistry that has no place in engines with high combustion temperatures. The reason? Those chemistries turn acidic at combustion temperatures and corrode bearings, rings, and camshafts surfaces.

Stick with a 40 grade HD or motorcycle oil engine oil with ZDDP levels showing ~ 1200 ppm of phos and zinc..
 
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