Vortex ROK Senior oil mix and fuel

What is the recommended fuel and oil mix for the Vortex Rok Senior engine, and what octane petrol should be used?
And does the engine need to run castor oil, or is it OK to run fully-synthetic two-stroke oil?

Thanks in advance😃

According to the ROK Cup Rules:

It says ROK GP runs 4% oil to fuel. That is equal to a 25:1 ratio or 5.12 oz of Oil per Gallon of Fuel. Also states to use a “High Quality Synthetic OIl” and a minimum Gasoline Octane rating of 95. Unleaded, Leaded or Race Fuel is okay. If you end up using Pump Gas, Make sure it is Ethanol Free and meets the minimum octane rating. Ethanol will play havoc on the jetting and eat up the seals in the carb. Underrated Octane fuel will detonate too soon and cause ignition timing issues, hot running conditions and possible engine failure from what I understand. Race fuel is best for consistency of quality and octane, but comes with a higher price tag.

@alvinnunley could probably weigh in more on the effects of fuel octane and timing.

If you plan on racing, always check the rules of your event as many club, regional and national events may have a spec fuel to run.

Hmm. It doesn’t specify the octane method they are referencing with 95. That’s a shame.

Unless you’re looking for last few hundreths, keep the timing at 3mm BTDC as recommended.

1 Like

Good evening, excuse me for bring this old topic back, but it’s a simular question.

When we say 4% oil ratio when mixing with fuel.

Do we mean 40ml of oil every 1liter of fuel.

So in 4 liters of fuel I should put 160ml of good castor oil?

I’m working on an vortex ex rok senior engine.

Good night mates.

Yes that’s how it’s made

1 Like

One of the manuals for the gp says research octane 95 which equates in America (r+m/2) to 90.7 octane (Google the conversion). Now most gas you’ll find in America will be e15 so if you want to avoid ethanol (I don’t see any reason NOT to avoid It besides price and convenience/ local availability) then you’ll need to find some ethanol free. If you’re lucky enough to live near Wawa they usually have ethanol free and if you’re worried about detonation (if your octane, timing, squish, and jetting are reasonable and within manual spec then you shouldn’t be worried about that) then dump in some leaded octanium octane booster from vp fuels.