[ST] Petro Rating

["Masiak, Richard" <Richard_Masiak@xxxxxxxxxxxxxxxx>]

You raise an interesting point when you said "Premium Unleaded fuel (95 RON I think)"

My RS manual says a minimum of 92 RON.  The way fuel is rated in the US is "octane" which is R+M/2  or RON + MON/2.

Pump gas and most race gasoline is rated in the (R+M)/2 fashion, which refers to an average of two ways that octane is measured: Research and Motor octane number. Research octane uses an industry-standard, single-cylinder test engine run at 600 rpm with an inlet-air temperature of 100 degrees Fahrenheit. Motor octane numbers are generated with this same test engine operating at 900 rpm with inlet air at 300 degrees F. Typically, Research octane numbers are 8 to 10 numbers higher than Motor octane numbers, since higher inlet air temperatures will increase an engine's tendency to detonate. There is an almost infinite number of ways to create the (R+M)/2 octane rating. According to Wusz, higher Research numbers will reduce part-throttle detonation, while higher Motor numbers are better for detonation resistance at wide-open throttle.

So how do we really know what the RON of a fuel?  I called several manufacturers like Texaco, Mobil, and Shell.  I could not get an answer from any of them.  My Triumph tech said that 89 octane usually should have a RON of 92, but it's not guaranteed.  I'm sure the numbers vary from batch to batch.

The best suggestion I got was to just try various manufacturer's 89 octane gas and watch for knocking.  As long as the engine doesn't knock you're fine.

So why do our wonderful engineers at Triumph spec. a Research Octane Number when the majority of fuels are rated using the average of the Research & Motor Octane numbers?

Rich

- -----Original Message-----
From: owner-st@xxxxxxxxxx [mailto:owner-st@xxxxxxxxxx]On Behalf Of
triumph1@xxxxxxxxxxxxx
Sent: Sunday, October 31, 2004 1:01 AM
To: ST@xxxxxxxxxxxxxx; CAPT Howard S. Serlick USNR
Subject: [ST] Re: TriumphSTDigest Mileage

>> 
I always use Premium Unleaded fuel (95 RON I think) and rarely do the speed limit ;)  On my previous Sprints with the standard gearing I was getting 18.5 - 19 kpl (covered about 70,000 km on those).

Mick in Aus
>>

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