Oil mixture 16 to 1 or?

Newer to karting. We have a kt100 engine racing in a jr super can division.

We’ve always mixed 16oz of caster or synthetic oil with 1 gallon of gas. This is equal to 2 bottles for every 4 gallons.

Another team mentioned that they run 2 bottles for every 5 gallons. Obviously less oil.

Is it recommended to run less oil in the gas? From what I read 16 to 1 seems to be the standard mix. Is there an advantage with less oil or would I be dancing with the devil and could damage the motor?

Also, if anyone knows these KT100 motor what octane is best?

Thanks for any replies.

Due to series regulations, we’ve only run VP C12 or MS98.
Either 2 or 2.5 16-ounce bottles of oil per 5 gallons of fuel works. I prefer 8 ounces of oil per gallon of gas.

Whoa, Whoa, Whoa, a 16 to 1 ratio is 8 oz of oil per gallon of gas. For a Yamaha KT100 that is the ratio that I would recommend.
16 to 1 is NOT 16 oz per gallon.


That’s 8:1 by volume, closer to 7:1 by weight. Did you know that spark plugs last more than one session for the rest of the field?

Since I have to take my cylinder off to look at the piston, I get to examine my engine’s internals a lot. Based on what I’ve seen, Phillips66 Injex oil mixed 6 ounces to the gallon (21:1) shows no scuffing on the piston or discoloration on the bearings of my TM.

I said 16 to 1. I meant 16oz of oil to 1 gallon of gas. That’s what I’ve been using. Just to clarify

Yes - that’s not a bad way to say it, it’s just the opposite of the way most people do - they either say “x ounces per gallon” or “x cc of gasoline to 1 cc of oil”.

Either way, 16 oz per gallon is a lot and you can save some money on oil and sparkplugs by using less.

Thanks. So not a performance issue. Just saves money and plugs.

You’ve got twice as much oil as you should though. I’d definitely go to 8oz/gal. Having the 16oz/gal will also put jetting/carburation out of ballpark making tuning recommendations that you may get as being irrelevant because the oil displaces they fuel. Essentially causing it to run leaner that it ordinarily would with the same settings.

James, I’m glad you brought up the jetting changes that can be attributed to oil ratio. It seems that most don’t think about that aspect of it. To me it’s more distinct in a fixed jet carburetor but it’s always a factor.
For those that are struggling with the 16-1 ratio, think about it this way, take the number of ounces in a gallon (128) and divide by the number of ounces of oil per gallon (8) and the answer is 16.

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KT100 I believe most run 8-10 ounces of oil per gallon of fuel with at least 110 octane race gas.

110 is often used, but it’s well above what they need. It makes tech easier and the lead is kind to bearings but they’ll run faster on a lower octane.

I think @DavinRS might have spent a few races scratching his head only to find out he had too much oil?

Popoff and oil ratio are two things I watch for when comparing carb settings. They are two very big variables.

You can certainly get away with lower octane gas, but you might be playing with fire detonation wise on a well built engine. Not to mention higher head temps with the quicker burn.

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A few years ago, I had that problem, but then I started running with a race team who gave me the guidance on oil mixtures. :slight_smile:

I’ve always looked at it this way: Fast burn is optimal when you have a tiny bore and fast RPM. There’s a limit of course, especially with air cooled.

Formula A 100cc engines ran lower octane fuels for this reason. As did JICA piston ports too. At a guess they laid down 20% more power vs a piped KT on around 98RON.

But no doubt, 110 leaded is very safe and kind to the internals. But I wouldn’t be unduly concerned with something like MS98.

I think the final decision comes down to availability

But anyway, I think we agree 16oz/gal is on the high side.