Gearbox wear: Mobile 1 vs Aeroshell

[NinerBikes]

Originally Posted by bobg56

Would the Mobil 1 be the type for motorcycles? This would be for the slip clutch that's for prop strikes?

Mobil 1 Racing 4T 10w-40 . Formulated with gearbox additive.

[Cammie Patch]

I just finished another 100 hour inspection on our RV12 (SLSA). We are putting about 70 hours a month on it.

About a month ago I ordered a new gear set and dog gear for the gearbox. If you remember, I couldn't idle much below 2500 rpm cold, due to vibration and gearbox chatter. I rebuilt the carbs, balanced them many times etc. But it didn't cure the problem. Aircraft only had about 120 real hours on it when we got it.

So, yesterday I cracked it open. I have to say that Sensenich is a bit barbaric in their prop/hub/bulkhead assembly on the -12. It's at least a two person job.
But, once I got it opened, I did see a lot of where on the dogs. Way too much wear for such a low time engine (about 400 hours now).

I wasn't happy to realize that CPS hadn't sent me the dog hub yet, just the gear set half. Since it's in a flight school, I had to put in what I had, and go with that for now.

But what a difference!! Now it runs smooth all the way down to 1600 RPM, with no chatter above 1800 rpm.

I'll open it up again when I get the other side of the dog gear and put that in.

The previous owner was very meticulous on how he operated it. He took Rotax and LSRI classes, and kept an incredibly well detailed report on each annual. He used AeroShell Sport 4 oil, and almost always used 91 octane fuel.

I have switched over to Mobile 1 4T oil. I have no other smoking gun than oil to blame for the early wear. I understand that Rotax has an obligation to promote the AeroShell oil, but I just don't think it's as good for the gearbox. I run about 95% mogas in the -12.

Another reference source: I just did an annual on a Tecnam SLSA, which has also been running the Aeroshell. It ran rough as well, with excess chatter.

http://www.glasscockpitaviation.com/...crc=4291031688

[pilotyoung]

That picture looks exactly like mine did after 450 hours. My engine has had Aeroshell Sport 4 Plus used in it since it was new.

[Cammie Patch]

I bought another SLSA RV12, and have seen the same wear in the gearbox, but the magnetic plug is pretty clean. I shimmed it up and switched oil. Still has some vibration, so I may crack it open again and replace the Bellville washers.

[NinerBikes]

Tach time on the new to you S-LSA ? And new pics if you open it up inside. Good data base being formed.

[rv3flier]

I suspect I may have the same problem. 235 hrs TT but it was completed in 2009 and I'm the third owner. Upon a cold start the engine seems smooth but when it starts to warm up I get a growling sound and more vibration. I was thinking it was the prop, but both blades were replaced early on by Sensennich due to a S/B and I just recently replaced the hub clamp due to the most recent S/B, had the carbs inspected, float height adjusted and the carbs sync'd. Anyone have a good idea of the cost to send the gearbox in for inspection/repair?

[Piper J3]

I now have enough runtime to share my experience with Aeroshell Oil Sport Plus 4 Vs. Mobil 1 Racing 4T 10W-40.

I bought my plane from original builder four years ago with 48TT. Engine had synthetic Mobil 1 Racing 4T 10W-40 in it from new. I changed oil at 50TT using Mobil 4T. I ran Mobil 4T for two oil changes and then switched to Aeroshell Oil Sport Plus 4 based on Rotax recommendations. After three oil changes with Sport Plus I have changed back to Mobil 4T. I use 93E10 Mogas exclusively and change oil at 75 hours.

My experience with engine oils is as follows? First two oil changes with Mobil required very little replenishment oil during 75 hours run. The three subsequent oil changes with Sport Plus each required one liter replenishment during 75 hours run. Now this latest oil change back to Mobil has again shown very little oil replenishment (2-3 oz) during 75 hours run. My plan is to stay with Mobil 4T.

Mobil 4T is full synthetic and formulated for 4-cycle engines with integral gearbox where engine/transmission share common lubrication system.

[NinerBikes]

Originally Posted by Piper J3

I now have enough runtime to share my experience with Aeroshell Oil Sport Plus 4 Vs. Mobil 1 Racing 4T 10W-40.

I bought my plane from original builder four years ago with 48TT. Engine had synthetic Mobil 1 Racing 4T 10W-40 in it from new. I changed oil at 50TT using Mobil 4T. I ran Mobil 4T for two oil changes and then switched to Aeroshell Oil Sport Plus 4 based on Rotax recommendations. After three oil changes with Sport Plus I have changed back to Mobil 4T. I use 93E10 Mogas exclusively and change oil at 75 hours.

My experience with engine oils is as follows… First two oil changes with Mobil required very little replenishment oil during 75 hours run. The three subsequent oil changes with Sport Plus each required one liter replenishment during 75 hours run. Now this latest oil change back to Mobil has again shown very little oil replenishment (2-3 oz) during 75 hours run. My plan is to stay with Mobil 4T.

Mobil 4T is full synthetic and formulated for 4-cycle engines with integral gearbox where engine/transmission share common lubrication system.

On a related note... I've owned a lot of various VW turbo diesel motors, and I've run Shell Rotella T6 5w-40 in all of them and Mobil 1 Turbo Diesel Truck 5w-40 in all of them. 10,000 miles between oil changes on all of them. The Rotella T6 oil changes all required make up oil of .75 to 1 qt between oil changes, and the Mobil 1 TDT required none. This was in 5 different model VW TDI's.

My friends RV-12 had 183 hrs on it when having it's 4th oil change, usually every 40-45 hrs with Shell. It goes through 3/8 through 5/8 of a liter of oil between oil changes, summer time has the higher oil consumption levels. It's my opinion that something is evaporating or burning off out of the Shell AeroSport 10w-40 motor oil, due to heat.

Owner likes to run 100LL, thinks it will make the carb floats last longer than E-10 mogas. Mogas and replacment Bing Carb floats are cheap compared to a gearbox overhaul and needing parts from Rotax to R&R.

I am not at all surprised by your findings. The only thing I am wondering is if the Mobil 1 T40 will increase longevity of the gearbox parts on the Rotax. If it does better in that area, it's a win, win.

I will be following Cammie Patch and their posts to see how that plays out. 70 hours a month flying time is a good bench mark to measure wear. 7 months is about 500 hours of run time.

The only limitation of the Mobil 1 T40 synthetic is no 100LL should be run with this motor oil. It doesn't handle lead in suspension.

[rvbuilder2002]

In making an oil usage choice, it is important to keep in mind that fully synthetic oil should not be used if leaded fuel (100LL) is being used very often.
Fully synthetic oil does not hold lead in suspension.

Sport Plus4 is semisynthetic. I think Mobil 4T is fully synthetic.

[NinerBikes]

Any updates on wear from the fleet from Cammie patch?