Premix?


8 replies to this topic
  • ttr250dude

Posted January 27, 2011 - 02:03 PM

#1

I'm sure this is a stupid question.. I've heard a few people here say that lead in gas can help cushion the valve seats. So, would running a premix of maybe 100:1 accomplish the same thing with out the expense of race gas? Would the extra minimal amount of lube benefit the rings or valves in any way?

  • grayracer513

Posted January 27, 2011 - 02:25 PM

#2

You're talking about what's called an upper cylinder lubricant, or simply. "top oil". That's a very, very old trick, but for the most part, it's no longer required. Using a top oil at 100-150:1 or so is still useful when you run a "dry" fuel in an engine, like straight alcohol, or some of the race gasolines on the market. Remember that the compression rings, valve seats, and guides are primarily lubricated only by the fuel in a four stroke, at least, one that has good oil rings and valve guide seals. But most modern gasolines fill this requirement well enough.

The old story about leaded gas "cushioning" the valves isn't everything it looks like it should be. Modern engines are built to run without it. Some manufacturers will even state that lead build up on the valve faces will damage the valves prematurely. In the long run, if you use any pump premium, you don't have to give the idea any thought.

Then again, if you add just a teaspoon of racing castor oil to your gas tank, all kinds of people will ask what kind of gas you're running. :thumbsup:

  • OldMechanik

Posted January 27, 2011 - 02:25 PM

#3

Valve seats are hardened...no need for lead.

  • ttr250dude

Posted January 27, 2011 - 03:53 PM

#4

So if I premix it will only help a minimal amount? I care more about longer top end service intervals than performance, but I'm guessing that since its such a little amount of oil I probably won't notice any difference. Right?

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  • grayracer513

Posted January 27, 2011 - 07:39 PM

#5

So if I premix it will only help a minimal amount? I care more about longer top end service intervals than performance, but I'm guessing that since its such a little amount of oil I probably won't notice any difference. Right?

Versus pump gas with no top oil? No difference at all that you will ever notice.

  • ttr250dude

Posted January 27, 2011 - 11:43 PM

#6

k. I'll just forget it. Would it be beneficial at all to run 100:1 during the initial break in of a fresh top end since the clearances r so tight?(pistons and rings)

  • grayracer513

Posted January 28, 2011 - 07:58 AM

#7

No, and it might even be counterproductive.

  • ttr250dude

Posted January 28, 2011 - 04:05 PM

#8

No, and it might even be counterproductive.


Interesting. How so? Would the extra oil not allow enough friction for the rings to seat properly?

  • grayracer513

Posted January 28, 2011 - 06:13 PM

#9

Possibly.





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