87 OCTANE

[Skeeve]

I think that our US pump #'s are RON. That's an average octane rating, if I'm not mistaken. I don't remember what units the owner's manual recommendation specifies. It's no matter, because I typically use Premium (91-93), which is the highest we can get, besides racing fuel. It doesn't surprise me that European fuel is better. Over here, it's quantity versus quality (all you can eat buffet, 4 for $1, etc.).

 

US pumps are PON = [MON + RON]/2

 

Worried about pinging? Go to the hardware store, buy some toluene, add to gas. Toluene's MON is up around 120, iirc. It's not cheap tho', but less expensive than the "special octane booster" stuff which is typically more methanol [bad for fuel lines, etc.]. Xylene is cheaper than toluene, but apparently the meta-, para- & ortho-xylols are terribly hard to separate, so the industrial solvents are a mix, & only the para? has a useful boost to octane rating. It's been a long time since I looked into all this, so don't quote me on the specifics, but the general idea is correct. Too bad the bulk rate xylene can't substitute for the toluene [which is now on the "suspect materials" list since you can make TNT out of it], as the mix of xylenes is about 2/3 the cost of toluene.

[Ryland3210]

US pumps are PON = [MON + RON]/2

 

Worried about pinging? Go to the hardware store, buy some toluene, add to gas. Toluene's MON is up around 120, iirc. It's not cheap tho', but less expensive than the "special octane booster" stuff which is typically more methanol [bad for fuel lines, etc.]. Xylene is cheaper than toluene, but apparently the meta-, para- & ortho-xylols are terribly hard to separate, so the industrial solvents are a mix, & only the para? has a useful boost to octane rating. It's been a long time since I looked into all this, so don't quote me on the specifics, but the general idea is correct. Too bad the bulk rate xylene can't substitute for the toluene [which is now on the "suspect materials" list since you can make TNT out of it], as the mix of xylenes is about 2/3 the cost of toluene.

 

I recall my Ph.D. chemist friend telling me how I could increase octane back when leaded was still on the market, and the first unleadeds were not available in high enough octane for my Barracuda. His recommendation was to fill my tank about 80-90% with unleaded regular, and the rest with leaded regular. It worked great!

 

So my question is, what ratio toluene to gasoline are you suggesting? Is it a simple weighted average of the pump octane number and 120, or is there a synergistic effect?

[Ryland3210]

You've personally inspected all US gas pumps? Amazing!

 

Fuel sales are taxed and regulated by individual states in the US, as are the labeling standards. The pumps around here are labeled with MON and RON figures. It may be different in CA or other states.

 

I think what he means is that the number on the big signs seen from the road is the average, "PON", and that is the uniform method used on those signs. What is on the pump is another issue.

 

If you think about it, since octane is not measured as delivered by the pump, an average of the two methods is a reasonable approximation of what actually goes into your tank. It makes sense.

[Skeeve]

I recall my Ph.D. chemist friend telling me how I could increase octane back when leaded was still on the market, and the first unleadeds were not available in high enough octane for my Barracuda. His recommendation was to fill my tank about 80-90% with unleaded regular, and the rest with leaded regular. It worked great!

 

So my question is, what ratio toluene to gasoline are you suggesting? Is it a simple weighted average of the pump octane number and 120, or is there a synergistic effect?

 

Unfortunately, there's no synergy w/ the straight toluene. The reason the mix you experienced worked so well is that back in the days of tetraethyl lead in gasoline, the amount req'd. to produce regular was x, the amount needed to produce hi-test wasn't x+2 [where the difference in octane rating was "2"], but closer to 2x! So the unleaded regular really responded to the amount of TE lead in the leaded regular, to get you something that was truly synergistic.

 

The only way to get that kind of f/x now is to get some 100LL from an airport [which for some reason they resist putting in a regular gas can, I wonder why that is? ] and spiking your mix. Obviously, nobody w/ a late-model Guzzi w/ catalyst or oxygen sensor in the exhaust plumbing should do this, or you're kissing some very ex$pen$ive components goodbye...

[Skeeve]

You've personally inspected all US gas pumps? Amazing!

 

Nah, I leave that up to the Bureau of Standards...

 

Fuel sales are taxed and regulated by individual states in the US, as are the labeling standards. The pumps around here are labeled with MON and RON figures. It may be different in CA or other states.

 

True, but all the pumps I've seen [yes, I actually read the little inspection stickers on the sides, etc. while standing around waiting for the tank to fill, probably due to my 1st regular job being hose jockey in a gas station] are [M+R]/2, and I kinda suspect the ICC would exert some Federal "suasion" on any state whose own Bureau of Standards allowed something besides the accepted norm. Call me a believer in bureaucracy!