Fuel Cap Minimum Octane Placard Question - Going Down the Rabbit Hole

[Dad's RV-10]

The Aerosport data plate on my IO-375 indicates the minimum octane rating is 91/96. 91/96 is an aviation fuel produced by Hjelmco Oil.

This article about UL91 says in part, "As an aside, remember that aviation fuels are usually denoted by their lean MON octane rating (MON = Motor Octane Number). Thus, 100LL = 100 MON and UL91 = 91 MON. Hjelmco still uses the lean/rich MON numbers to denote their fuel, thus Helmco’s 91/96UL would be the same as a 91 MON aviation fuel. To add to the confusion, most countries denote octane ratings for highway vehicles according to their RON (RON = Research Octane Number), except the US, which uses the Anti-Knock Index, AKI (AKI = (RON+MON)/2 )..."

It seems that 91/96 is the same as 91 aviation fuel but not the same as 91 auto fuel.

So what should a fuel tank placard indicate for this engine? Simply "Min Octane 91/96"?

If it were to say "Min Octane 91," one might assume 91 auto fuel is acceptable.

This is likely minutia but I'm curious to hear some thoughts.

Thanks.

 

[David Z]

Fuel cap placard could say something similar to "gasoline grades as approved by aircraft flight manual"

Says "gasoline", so warns against mis-fuelling with Jet A. Then refers to the flight manual that can be easily amended as different grades of gasoline are developed and assessed for suitability.

 

[Mel]

Fuel cap placard could say something similar to "gasoline grades as approved by aircraft flight manual"

Says "gasoline", so warns against mis-fuelling with Jet A. Then refers to the flight manual that can be easily amended as different grades of gasoline are developed and assessed for suitability.

Fuel cap placard must indicate minimum octane and tank quantity.

This information is primarily for the "line boy" so that he/she knows how to fuel your aircraft. He/she does not have access to the flight manual.

 

[Auburntsts]

IAW Lycoming Service Instruction No. 1070AB mine are engraved with 91 MIN OCT. Below that is second line that says 30 US GAL.

 

[BobTurner]

Many years ago I had an STC for car gas in a low compression 182. They sent a placard that said “Av Gas 80 or Auto gas 87”

 

[rmarshall234]

I'm into minutia as well and just went through the same exercise. Why not just add the words Aviation Fuel or Av Gas to what you've decided already? That should eliminate the concern of someone adding car gas. I went a step further... IAW Lyc SI 1070AB (mentioned already) I labeled mine: UL91. In anticipation of the switch-over to unleaded aviation fuel which is coming _soon_.

 

[MacCool]

My gas caps currently say "100LL - 36 gallons". If and when G100UL is on the fuel truck, I'll get new ones and engrave them "AVGAS 91 OCT MIN - 36 GALLONS"

 

[PilotjohnS]

????

My gas caps currently say "100LL - 36 gallons". If and when G100UL is on the fuel truck, I'll get new ones and engrave them "AVGAS 91 OCT MIN - 36 GALLONS"

36 gallons each wing in the RV9A??
My stock RV9A has 18 gallons per tank; so my stickers say 18 gallons. Min oct 91.

 

[Dad's RV-10]

..."AVGAS 91 OCT MIN - 36 GALLONS"

That'll probably fit on an engraved cap without too much difficulty. I like it!

Thanks for the feedback.

 

[Mel]

That'll probably fit on an engraved cap without too much difficulty. I like it!
Thanks for the feedback.

For many, many years, I've been preaching that lead content is not required on the placards.

When 100LL goes away, I'll be going into the fuel cap engraving business!

 

[Auburntsts]

That'll probably fit on an engraved cap without too much difficulty. I like it!

Thanks for the feedback.

I recommend leaving off “AVGAS” and just put the Min Oct (plus the gals).That way affords you the most flexibility.

 

[MacCool]

36 gallons each wing in the RV9A??
My stock RV9A has 18 gallons per tank; so my stickers say 18 gallons. Min oct 91.

Yeah. 18 gallons per tank. I'll get it right by the time I have to order the new caps. Plenty of time, I'm guessing. Local FBO in in denial, I think, even though they contract with AvFuel.

 

[swjohnsey]

Mine just say 100 LL. Am I in trouble?

 

[Dad's RV-10]

I recommend leaving off “AVGAS” and just put the Min Oct (plus the gals).That way affords you the most flexibility.

Maybe some Déjà vu for you?

 

[Mel]

Mine just say 100 LL. Am I in trouble?

The requirement is for minimum octane and tank capacity.

 

[Taltruda]

The requirement is for minimum octane and tank capacity.

Where is this “requirement” written? I totally agree that we SHOULD have it placarded, but I can’t find the reg.

 

[Larco]

Would love to see the regulation as well. Have had respected FAA inspectors and/or DAR's with opposing opinions on this regarding EAB. Even had one tell us the caps had to be painted red to get signed off. Red they are on that RV.

On our current RV they are marked so no gripe here, no disrespect intended but wish there was more agreement between FAA reps and/or DAR's regarding EAB regulations?
.

 

[BobTurner]

As discussed ad nauseum, having ‘octane’ on the placard, when these days there are alternative fuels, is borderline useless. It should say ‘motor octane’ or if appropriate ‘auto octane (aki)’, etc.

 

[RV6_flyer]

Where is this “requirement” written? I totally agree that we SHOULD have it placarded, but I can’t find the reg.

The DAR and inspectors must follow the ORDERS issued by the FAA. The latest version of FAA Order 8130.2J Section 17-3 c. (9) requires fuel tank placard, manual(s), and all documents identify the same fuel requirements.

I retired being a DAR 10-years ago and use to point people to a different paragraph in an earlier version of that document when asked about where the requirement came from.

FAR 91.9 (b) (2) is the catch all requirement for a placard that may be messing some inspectors up.

 

[Taltruda]

The DAR and inspectors must follow the ORDERS issued by the FAA. The latest version of FAA Order 8130.2J Section 17-3 c. (9) requires fuel tank placard, manual(s), and all documents identify the same fuel requirements.

I retired being a DAR 10-years ago and use to point people to a different paragraph in an earlier version of that document when asked about where the requirement came from.

FAR 91.9 (b) (2) is the catch all requirement for a placard that may be messing some inspectors up.

Thank you for this reference. I absolutely agree that experimentals should placard their tanks IAW FAR 23.1557 (which doesn’t apply to EAB) I’m still not convinced or should I say not clear on the required markings.
For reference, that FAA order above states:
(9) Consistency Among Documents. Verify that data contained in the documentation (such as the maintenance manuals, AOI, placards, and other manuals incorporated by reference) is consistent. For example, the AOI, maintenance manual(s), and aircraft’s fuel tank placard all identify the same fuel requirements (with conversion noted).

Since EAB isn’t required to have a flight manual, or maintenance manual.. I guess I’m hoping to find a clearly stated requirement on what the fuel filler needs to state. Once again, I’m an advocate for placarding type of fuel and tank capacity, I just wanted the reference that backs it up.

 

[gasman]

The DAR and inspectors must follow the ORDERS issued by the FAA. The latest version of FAA Order 8130.2J Section 17-3 c. (9) requires fuel tank placard, manual(s), and all documents identify the same fuel requirements.

I retired being a DAR 10-years ago and use to point people to a different paragraph in an earlier version of that document when asked about where the requirement came from.

FAR 91.9 (b) (2) is the catch all requirement for a placard that may be messing some inspectors up.

Not to add confusion, but it looks like this section applies to LSA certification.

 

[Scott Hersha]

Mine - 100LL / 19 gal. - on a clear label maker placard. When something changes (likely), I’ll peel it off and make another one.

 

[Webb]

The requirement is for minimum octane and tank capacity.

What does Mel recommend engraving on the gas cap for type of gas used now and what will be used in the future?

I guess 2 examples are needed. Avgas only and avgas/auto gas.

 

[Mark33]

Is this a “ramp check” issue or a DAR checklist item?

 

[Taltruda]

Fuel cap placard must indicate minimum octane and tank quantity.

Mel, I agree, and my caps are labeled as such, however, I would like to have that reference so I can be more educated when this topic comes up on condition inspections. Thanks!

 

[Desert Rat]

for the OP. If it were me, I'd say "Min Octane 91/96" and the quantity. It matches what's on the data plate and satisfies the requirement.

I'd probably then put a note in the preflight checklist and the systems section of my POH if I had one.

If you start getting down in the weeds with all kinds or exceptions and "yeah but" statements on your fuel caps you're only going to make it harder on yourself.

 

[N82VM]

Here’s what I did. I could/should have left off the “UL 91”

Data used from Table 3 of the Lycoming Service Instruction for the IO-360-M

for the OP. If it were me, I'd say "Min Octane 91/96" and the quantity.

I did not use the word “octane” because the regs refer to it as minimum “grade”. Table 3 has “aviation fuel, automotive fuel”. AVGAS and MOGAS respectively are accepted terms. In addition Table 1 and 2 describe the fuel in Table 3 in terms of “Grades”. Octane may not be the best choice since the Lycoming SB does not use it nor does the FAA reference it that way either.

As far as ethanol is concerned it’s an oxygenate, the Service Instruction allows such a small amount that in practicality it means no ethanol since you’ll be hard pressed to find it with that little in it. It’s E-AB but I’m sticking with the Lycoming instructions.

(1) Fuel filler openings must be marked at or near the filler cover with—
(i) For reciprocating engine-powered airplanes—
(A) The word ‘‘Avgas’’; and
(B) The minimum fuel grade.