fuel

[justin606]

i have always went with 32:1 but was just wanderin what is the best ratio to go with.

[05450r]

I personally used 32:1 in the past, and tried 40.1 more recently.

[Piney0]

IMO, the best ratio is the one recommended on the bottle.  Too many types of oil / blends to have a perfect ratio for all of them.  I run 32:1 with maxima 927.

[fearlessfred]

32 to 1 seems to be best for a 250 motor what think is really interesting is that you can make more power wih more oil and not less.I guess I should add that you could go to far with that .jerry hall was recently commenting on that on another post

[justin606]

.... 32:1 it is then . i was asking because i saw were a lot of people run 40:1 and other ratios so i just wanted to get an opinion from someone else thanks

[bnau267]

I've seen posts of people running 50:1 with Amsoil.  Seems crazy to run a bike on the same ratio as my Stihl.  I've been running 32:1 for the past twenty years.  Btw - Caster 927 smells great.

[Jerry Hall]

As one gains experience I think you will find that the amount of oil that is needed in the fuel depends upon the RPM and the throttle position.  Many years of observation of related lubrication related failures seems to fit the same science that guides the engine manufactures that use oil injection on their two strokes.  High RPM and wide open throttle needs more oil in the fuel than low RPM and partial throttle.  Mix you oil and fuel for the worst case situation that you may subject your engine to experience.

[rablack21]

32 to 1 seems to be best for a 250 motor what think is really interesting is that you can make more power wih more oil and not less.I guess I should add that you could go to far with that .jerry hall was recently commenting on that on another post

I agree and disagree with this. I don't disagree that a more concentrated ratio might make more power than a higher ratio. I disagree with that "32:1 seems to be the best for a 250r" motor. If the oils only job is to make the most power, then that might be true. However, 3 purposes should be factored into an oil: protection, cleanliness, power (in that order, with power being the least important). The quality of the oil will also factor into this equation. The poorer the quality of the oil, the more will need to be used to achieve adequate protection.

I've seen posts of people running 50:1 with Amsoil.  Seems crazy to run a bike on the same mix ratio as my Stihl.  I've been running 32:1 for the past twenty years.  I even ran my bike mix in the old Lawnboy.  I miss those two stroke mowers...stupid EPA.   Btw - Caster 927 smells great.

I race my engine with Amsoil Dominator @ 50:1 with zero issues. Will it make the most power at 50:1, maybe not. But that's not the most important. It is the best combination of the oil's purposes that is important. An oil's first job is to protect. Yes, a poorer quality oil may need to be mixed at a lower ratio to compensate for poor protection characteristics. The next job of an oil is to burn clean enough to not hinder the engine with build up. Carbon build up will lead to a variety of problems including premature failure. The oil mixture providing more power is the least important characteristic to most riders.

Now with that said, if you are a drag racer or someone who tears down their engine after every use, then power would be the most important. And in this case the oil's purposes would shift in order. I do also agree with the guy that said, run what the ratio on the bottle says. This is a good rule of thumb.

[udontknowme]

ive always used alot of oil in my mix. benol to be exact. but recently i was reading into what the fastest gp bikes were using and its around 20:1. that was proof enough for me what a high revving engine should need

[05450r]

If you ask the old school guys,thicker/more oil boosts/holds compression

[fearlessfred]

I really wouldn't argue with what you have said,Im sure amsoil has done enough testing to know what ratio there oil needs to be . I have allways ran yamalube and at 32 to 1  the rings don't get all gunked up and sticking and the motor will have a long life at that ratio. a motor that comes apart often could use more oil for more power In the past when all I rode was an r I would put an easy 100 hour on a piston before changing

[Jerry Hall]

If you ask the old school guys,thicker/more oil boosts/holds compression

The primary reason that I recommend using a lot of oil is to improve the heat transfer from the heat sources to the heat sinks. Very good oil at 60:1 may lubricate much better than the worst oil at 15:1, but the engine using the 15:1 ratio will dissipate heat from the piston and bearings better than the engine using the 60:1 ratio.  When more oil is put in the fuel, the oil film thickness on all of the surfaces inside of the engine crankcase increases in thickness regardless of the brand of oil.

On a dry cylinder wall, the piston will conduct heat to the cylinder wall only where the piston and rings make contact with the cylinder wall.  If we look at the surface of the piston and the cylinder wall under a microscope, we will see contact is made only where the peaks of the tool marks on the piston and the peaks of the crosshatch on the cylinder wall are touching each other.  

If we wet the machined surface with a very thin layer of oil, the oil partially fills the voids between the tool marks and the peaks of the crosshatch.  Now heat is conducted at the peak-to-peak contact of the two metals as well as anywhere the oil film touches the two metals simultaneously.  The conductive heat path is always increased when the oil film thickness is increased.   The same principle also applies to ball and roller bearings in a two-stroke engine.


Two stoke engines will usually make a little more power with certain oils because the low oil ratios increase the film thickness and helps improve the seal between the piston skirts and the cylinder wall as well as the seal between the piston ring and ring gland in the piston and the ring and cylinder wall.  My experience has shown that many of the full synthetics will not make good power at ratios in the range of 15:1 to 30:1

[fearlessfred]

thanks jerry,I learn a little bit each time you and arlan post

[wilkin250r]

Jerry, great posts, but give a suggestion man!  While people love information and obviously respect your opinion, they're also looking for ANSWERS from those they admire.  Even if it's four different suggestions in one, give the people what they want!

Personally, I run 40:1, but don't follow my lead blindly because you respect my opinion until you read my ridiculous reasons for choosing that particular ratio.

1) It's within manufacturer's specifications, and they do more testing than I do.

2) I'm lazy.  My gas cans are 5 gallon, and oil is available in 16oz containers.  Perfect 40:1.  I hate those messy measurement cups.

My personal suggestion for others would be at least 32:1, unless your revving piss out of your motor all the time, then maybe a little richer on the oil.

[Brett]

I run Amsoil Dominator at 30:1 on my 310. No excessive build up for me and I could probably run a leaner mix but I'm paranoid.

-Brett-