RAA MEMBER AND SUBSCRIBER NEWSLETTER 2 July 2026

[facthunter]

Comparing spark Plug brand to a special oil has limited value.  Almost no relevance at all. The problem with the oil is you are asking it to perform often Opposing things because of the way the engine is designed. The friction required in  a clutch is inconsistent with  reducing it elsewhere and Lubing hot gears.  Any Power loss in a gear train results in Heat as does the (required) clutch friction. and there's long periods of no Let-up.  1 or 2 percent would be a two bar radiator output and that's way under what is Probably happening.. Nev

[Blueadventures]

On 03/07/2026 at 5:22 PM, T510 said:

I'm with Skip on this one. I don't think it is appropriate behavior from RAAus.

 

 Regarding oil standards, they are well established and have been around for over 100 years.

 

Rotax originally specified a high-quality 4-stroke motorcycle or aviation oil with an API classification of "SG" or higher because the engine features an integrated gearbox. They also stated gear additives are required, but no friction modifiers should be used. Plenty of Rotax's are around that have been running oil that meets that requirement without destroying themselves.

 

While SG is now obsolete, any modern API SP, SN, SM, SL, or SJ motor oil is a direct equivalent to the obsolete API SG rating. Current API classifications are fully backwards compatible with earlier classifications.

 

That was likely back at the period when the blend of the Sport Plus 4 was altered by shell, black bottles to the red bottle.  At the time it was strange that the sport plus 4 blend was changes and the branding retained.  Then the high quality motorcycle oils became inappropriate.

[BurnieM]

Sorry I went off at a tangent.

 

The point was that complying with  everything an aviation manufacturer says 100% may in some cirumstances be required but to do it blindly can also get you killed.

[skippydiesel]

2 hours ago, Blueadventures said:

That was likely back at the period when the blend of the Sport Plus 4 was altered by shell, black bottles to the red bottle.  At the time it was strange that the sport plus 4 blend was changes and the branding retained.  Then the high quality motorcycle oils became inappropriate.

I didn't want this Thread to be about oil, but if you cant beat the divergents, you might as well join in.

 

 

"......blend of Sport Plus 4 was altered by shell, black bottles to the red bottle."

 

Do you know for a fact ,that the Sport Plus 4 Black Bottle oil, was chemically any diffrent to what was in the Red bottle?

 

FYI: When talking oils its usual to use the term  formulation, blending is what they do with wine, whiskey, cake mixes etc.

 

What is "...inappropriate..." about using an oil, which meets/exceeds the specifications set by the manufacturer (Rotax)???? 

 

Many of the early Rotax 912's, that used an appropriate oil, are still going today & still using  the same oil, that meets the above specifications.

 

😈

[Blueadventures]

26 minutes ago, skippydiesel said:

I didn't want this Thread to be about oil, but if you cant beat the divergents, you might as well join in.

 

 

"......blend of Sport Plus 4 was altered by shell, black bottles to the red bottle."

 

Do you know for a fact ,that the Sport Plus 4 Black Bottle oil, was chemically any diffrent to what was in the Red bottle?

 

FYI: When talking oils its usual to use the term  formulation, blending is what they do with wine, whiskey, cake mixes etc.

 

What is "...inappropriate..." about using an oil, which meets/exceeds the specifications set by the manufacturer (Rotax)???? 

 

Many of the early Rotax 912's, that used an appropriate oil, are still going today & still using  the same oil, that meets the above specifications.

 

😈

You prove me wrong.

[skippydiesel]

Dear Blue - You made the claim (s). The ball remains in your court, never to leave it, until you demonstrate the truth (?) in your words.😈

Edited yesterday at 09:36 AM by skippydiesel

[walrus]

The manufacturers lubrication recommendation may have nothing to do with "performance" in the power or reliability sense of the word, in fact it may even be sub optimal from a performance viewpoint.

 

For example, it is already acknowledged  in certain automotive circles that low viscosity oils are often specified to help meet cold start emissions requirements when in fact something heavier may be better for longevity. However there are conditions that we know nothing about that my make oil choice less obvious, for example foaming, behaviour of oil drainage systems or dry sump systems or pump cavitation, etc. We have to trust the manufacturer or do research ourselves.

[Blueadventures]

1 hour ago, walrus said:

The manufacturers lubrication recommendation may have nothing to do with "performance" in the power or reliability sense of the word, in fact it may even be sub optimal from a performance viewpoint.

 

For example, it is already acknowledged  in certain automotive circles that low viscosity oils are often specified to help meet cold start emissions requirements when in fact something heavier may be better for longevity. However there are conditions that we know nothing about that my make oil choice less obvious, for example foaming, behaviour of oil drainage systems or dry sump systems or pump cavitation, etc. We have to trust the manufacturer or do research ourselves.

I suspect the reason Shell changed the Sportplus4 blend 12 or so years ago was due to the effect on the gearbox performance, at the time I thought it was a bit poor that they did not change the brand name (reckon they should at least called it Sportplus4 extra or something to distinguish it from the earlier blend that was in a black bottle and no longer suitable.  This then saw the automotive similar grades now being not suitable anymore.

Edited yesterday at 11:30 AM by Blueadventures

[Thruster88]

Aeroshell 100 also changed from black to red bottles in 2014, same formulation. 

[skippydiesel]

11 hours ago, Blueadventures said:

I suspect the reason Shell changed the Sportplus4 blend 12 or so years ago was due to the effect on the gearbox performance, at the time I thought it was a bit poor that they did not change the brand name (reckon they should at least called it Sportplus4 extra or something to distinguish it from the earlier blend that was in a black bottle and no longer suitable.  This then saw the automotive similar grades now being not suitable anymore.

Your doing its again - Is making unsupported (& unlikly) observations a habit?😈

[facthunter]

Another Important subject that is going nowhere. Here. Mostly just opinions.  The 80 hp Rotax is nothing like as stressed as the later ones. It WAS about Rotax's oil recommendation and to suggest using their oil recommendation is not the safest is somewhat ridiculous. Oil makers often change their formulations and it even varies in different countries at times. You can easily get into "NO Man's Land" when you recommend alternatives today.

[T510]

12 hours ago, Blueadventures said:

I suspect the reason Shell changed the Sportplus4 blend 12 or so years ago was due to the effect on the gearbox performance, at the time I thought it was a bit poor that they did not change the brand name (reckon they should at least called it Sportplus4 extra or something to distinguish it from the earlier blend that was in a black bottle and no longer suitable.  This then saw the automotive similar grades now being not suitable anymore.

How does an oil become "not suitable anymore" when it was suitable from 1989 when the 912 series was released.

 

Obviously different 912 models and derivatives may require different oil grades but if you have been using brand "x" oil for 20 years with no issues it begs the question how it becomes no longer suitable and why is a change required.

 

A change in the SportPlus4 formula (if there was one, I don't know) doesn't make previously suitable oils no longer perform at the level required.

Edited 18 hours ago by T510

[facthunter]

To stop catalytic  converter deterioration a lot of oil formulations had to be changed and some friction Modifiers discontinued. It's one of the reasons roller camshaft followers became more common. Nev

[BurnieM]

Pretty much ALL of the (4 stroke) motorcycle oils will still work in Rotax aviation engines as they are designed for combined engine/gearbox/clutch use with no friction modifiers. Just pick the right temperature range.

 

Mineral oils may break down earlier in some of the hotter Rotaxs.

Semi synthetic probably work in most.

Full synthetic would be good for higher temp engines. Most (all?) of the mc oils would not suspend lead in 100LL properly as mc never use it.

Full syn should work fine with long engine life if you only use mogas.

 

Yes, I am not an expert but a mate is a lab tech for Shell (previously Castrol) and I believe this is an informed opinion.

 

Edited 17 hours ago by BurnieM

[facthunter]

None of what you say is very scientific. Camshaft lobes are a critical Lube point and the Rotax doesn't have roller followers so would REQUIRE some anti-scuffing additives. Should , may and probably don't go far in court. OIL for Gears and a clutch at the same time is a compromise.ie Not optimum for either situation. .. Nev

[BurnieM]

You are right, I have not broken it down by requirement and additive used as I lack the expertise.

This does not take away from the fact that motorcycle oils have been perform high quality, multi function lubrication at high revs and temperatures over a very long time period.

There is nothing special in Rotax aviation engines and Rotax have been making motorcycle and snowmobile engines for a significant time.

 

Yes I am not talking about legal requirements. I am concerned about safety and engine failure modes and dying.

 

[facthunter]

You can easily look this up. Ask Why do the Later Rotax9xx Motors Need fancy/special oil? Mostly things I have been  saying, and very easy to understand.. What are you saying about dying.?? Surely ignoring a Rotax recommendation INCREASES that Possibility?  If you want common engine failure Modes/ causes, I'm sure that is mentioned in Plenty of places also. The Aero orientated 9xx motors are a very small % of Rotax's total engine output.. Nev

[FlyBoy1960]

The history of AeroShell Sport Plus 4

The story really begins with the unique design of the Rotax 912 series.

Unlike traditional aircraft engines from Lycoming Engines or Continental Aerospace Technologies, the Rotax engine is much closer to a motorcycle engine than a conventional aircraft engine.

It has:

• liquid-cooled cylinder heads
• air-cooled cylinders
• an integrated reduction gearbox
• an overload clutch
• shared engine/gearbox oil
• relatively high RPM (up to 5,800 rpm)

That immediately created a problem.

 

Traditional aviation oils were designed for slow-turning direct-drive aircraft engines.

Motorcycle oils were designed for gearboxes but weren't designed for aviation fuel contamination.

Neither was ideal.

---

Before Sport Plus 4

During the 1990s and early 2000s Rotax recommended a range of motorcycle oils depending on fuel type.

Many operators used:

• Mobil 1 Racing 4T
• Castrol Power 1
• Motul motorcycle oils
• various semi-synthetic motorcycle lubricants

These generally worked well when operating exclusively on unleaded mogas.

The problem came when using 100LL Avgas.

Leaded aviation fuel creates lead salts during combustion.

Those deposits have to remain suspended in the oil until the next oil change.

Many fully synthetic motorcycle oils were poor at handling this contamination, allowing lead sludge to build inside the engine and oil tank.

---

Shell and Rotax begin working together

Around 2004, Shell and Rotax began collaborating to develop an oil specifically for Rotax aircraft engines. Rather than adapting an existing automotive or motorcycle lubricant, they worked toward an aviation-specific formulation that addressed the engine, gearbox, overload clutch, and fuel-related issues together.

This development programme lasted roughly three years of testing.

---

2015 – AeroShell Sport Plus 4 is released

In March 2015, Shell introduced AeroShell Sport Plus 4.

It wasn't simply a rebranded motorcycle oil.

It became the first aviation oil:

• designed specifically for Rotax engines
• tested jointly with Rotax
• approved to the new Rotax oil specification RON 424

At that point Rotax revised its service information to make Sport Plus 4 its recommended oil.

---

Why Rotax wanted its own oil specification

Rotax realised its engines had requirements unlike almost every other piston aircraft engine.

The oil has to simultaneously:

✓ lubricate crankshaft bearings

✓ lubricate the gearbox

✓ protect the overload clutch

✓ resist gearbox shear forces

✓ suspend lead from Avgas

✓ prevent clutch slip

✓ resist foaming

✓ flow well in cold weather

✓ maintain viscosity at high temperatures

That combination simply wasn't covered by existing aviation oil standards.

So Rotax created RON 424.

Only oils passing extensive testing against this specification are officially approved.

---

What exactly is Sport Plus 4?

It is not a full synthetic.

It is best described as a semi-synthetic (synthetic technology) multigrade aviation lubricant.

SAE viscosity:

10W-40

Typical properties include:

• Pour point: -39°C
• Flash point: 228°C
• Excellent cold start flow
• Strong anti-foam package
• High shear stability
• Zinc/phosphorus anti-wear additives (ZDDP chemistry)

---

Why not use ordinary aviation oil?

Traditional aviation oils such as:

• AeroShell W100
• AeroShell W80
• Phillips XC

are "ashless dispersant" oils.

They work brilliantly in:

• Lycoming
• Continental

They should not be used in Rotax 912-series engines because they are not formulated for the integrated gearbox and wet clutch system.

---

Why not use ordinary motorcycle oil?

Motorcycle oils are actually much closer to what the Rotax needs because they also lubricate:

• gearbox
• clutch
• engine

However there are drawbacks.

Some motorcycle oils:

• don't suspend lead effectively
• aren't tested for aviation duty cycles
• may not provide optimum corrosion protection for aircraft use
• aren't approved to RON 424

If you exclusively use premium unleaded mogas, many owners have historically had good results with quality motorcycle oils. If you regularly use Avgas 100LL, the dedicated aviation formulation of Sport Plus 4 offers clear advantages in handling lead contamination.

---

Lead handling

One of the biggest engineering achievements of Sport Plus 4 is its ability to suspend lead.

Remember:

100LL contains tetraethyl lead.

That produces:

Lead bromide

Lead oxide

Lead salts

If these settle out they can block:

• oil passages
• oil tank
• gearbox
• hydraulic tappets
• oil jets

Sport Plus 4 uses detergents and dispersants specifically selected to keep these contaminants suspended until the oil is drained.

---

Gearbox protection

This is probably the most overlooked feature.

The Rotax gearbox creates extremely high shear loads.

Ordinary automotive oils can shear down rapidly.

Sport Plus 4 was formulated specifically to:

• maintain viscosity
• protect gearbox gears
• protect the overload clutch
• reduce gear wear
• minimise foaming

This is one reason Shell emphasises its high shear stability.

---

Engines approved

Originally it covered:

• Rotax 912
• Rotax 914

Today it is also approved for later four-stroke Rotax families, including the Rotax 915 iS where specified by Rotax documentation.

---

Oil change intervals

The oil itself doesn't determine the interval.

Fuel does.

Typical Rotax guidance has long been approximately:

• 100LL Avgas: around 50 hours
• Premium unleaded mogas: up to 100 hours (subject to the engine model and current Rotax maintenance schedule)

The shorter interval with Avgas is driven by lead contamination rather than lubricant degradation.

---

Why many mechanics like it

Most Rotax maintenance organisations appreciate that Sport Plus 4:

• produces clean engines
• has low sludge formation
• provides excellent gearbox protection
• gives reliable cold starts
• has consistent quality worldwide
• is backed by Rotax testing and approval

---

Criticisms

No product is without criticism.

The main complaints are:

Price

It is usually more expensive than motorcycle oils.

Availability

Some regional suppliers don't always have stock.

Exclusive recommendation

Some owners believe Rotax's recommendation reflects a commercial partnership with Shell, while others point to the technical testing behind the RON 424 approval. Regardless of those opinions, Sport Plus 4 is the oil that Rotax specifically tested and approved to its current specification.

---

My view after many years of Rotax operation

For aircraft that:

• occasionally use 100LL,
• have expensive gearboxes,
• or are operated commercially,

AeroShell Sport Plus 4 is difficult to fault. It was engineered specifically for the unique combination of engine, gearbox, clutch and mixed-fuel operation that defines the Rotax 912 family.

For aircraft operated only on premium unleaded mogas, quality motorcycle oils have historically given satisfactory service for many owners, but they lack the formal RON 424 approval and the dedicated aviation validation that Sport Plus 4 has received.

Given the cost of a Rotax engine overhaul, the price difference between Sport Plus 4 and a less expensive alternative is relatively small over the life of the engine, which is one reason many Rotax specialists continue to recommend it.

 

MIKE DROP !!!

[skippydiesel]

FlyBoy 1960

 

WOW!!

 

 Other than the undue emphasis on AvGas use (Rotax 9's are designed for ULP, with grudging allowance to use part of whole AvGas) the above should dispel ALL the weird left of field commentary😈

Edited 15 hours ago by skippydiesel

[Blueadventures]

Sportplus 4 oil new formulation.pdf

 

Sportplus 4 oil new formulation.pdf

 

My reference is to pre  March 2015, Shell introduced AeroShell Sport Plus 4, the earlier AeroShell Sport Plus4 oil.

Edited 14 hours ago by Blueadventures

[T510]

4 minutes ago, Blueadventures said:

 

Sportplus 4 oil new formulation.pdf 678.73 kB · 1 download

Interesting to see they give a JASO standard alongside the Rotax RON 424 standard

 

"JASO MA is a Japanese standard for four-stroke motorcycle oils. It certifies that the oil has the correct frictional properties to prevent clutch slippage in bikes with shared engine, gearbox, and "wet" clutch systems, and contains minimal friction modifiers"

 

Does that mean other JASO MA standard oils are compatible?

[Blueadventures]

1 minute ago, T510 said:

Interesting to see they give a JASO standard alongside the Rotax RON 424 standard

 

"JASO MA is a Japanese standard for four-stroke motorcycle oils. It certifies that the oil has the correct frictional properties to prevent clutch slippage in bikes with shared engine, gearbox, and "wet" clutch systems, and contains minimal friction modifiers"

 

Does that mean other JASO MA standard oils are compatible?

Seems they came in line and improved the existing Sport Plus 4 oil blend in 2015 to the market.

[skippydiesel]

52 minutes ago, Blueadventures said:

Sportplus 4 oil new formulation.pdf 678.73 kB · 3 downloads

 

Sportplus 4 oil new formulation.pdf 678.73 kB · 3 downloads

 

My reference is to pre  March 2015, Shell introduced AeroShell Sport Plus 4, the earlier AeroShell Sport Plus4 oil.

Its  a  very old marketing ploy, to claim you are releasing new & improved product onto the market, when all you are doing is repackaging (black- red) - normally just words.

 

Where does it state that the formulation (blend to you) has actually changed ie documented change of standards and or specification sheet (one for the black bottle & one for the red).

 

😈

 

[FlyBoy1960]

perhaps they have a different standard in Japan because they don't have the sport plus oil available in that market ?

[facthunter]

You never give up, do you Skip.?  The big problem with 100LL was that the  Valve seats built up a deposit as the valve seats didn't get Hot enough to make the tetra-ethyl lead Melt and work as a flux/lubricant and it showed up AS poor compression readings. The Bromide was an additive to the fuel to clear out the Lead deposits and produced the telltale white exhaust pipes  of the time. Bronze  heads couldn't accept lead as the seats in the Head deteriorated due to the Metal picking up on the valve itself.  Its only later when Nickel iron seats were able to be inserted in the Bronze heads, and reliably remain there that 100LL could be used on those motors. 100LL is Low Lead compared to other Leaded fuels of the 60'swhich were a lot higher octane. 130/145 was most used. 130 being the Octane of a lean mixture. The Octanes don't correlate with SAE ones which perform  WORSE for the same number , If you are really into Oils research what Low Ash oils are for. All Aero oils are Low ash to stop Metallic (zinc and phosphorus) additives Accumulating in the combustion chambers and lube oil. These can also short out spark Plugs. Oils can contain up to 45% additives .Early aero oils specified Pennsylvanian crude as a requirement.  It's recognised as the Best. Nev

Edited 12 hours ago by facthunter