Yep with Mobil 1 Racing 2T all you need to do is follow the manufacturer's ratio. I just switched my 2 cycle equipment over to the 2T today and right away I noticed virtually no smoke.

I'm sure you might know which oil I use, but mix it @ 40:1. 32:1 is just not necessary with a fully synthetic like Mobil 2T. If you've run Amsoil @ 50:1 with no issues, 40 will more than cut it for other synthetics. 32:1 will work of course, but you may experience a bit more oil residue and pooling in and around the muffler. LB engines just won't rev or load high enough to burn off all the synthetic esters.

In my Lawn Boys I use Mobil 2T at 32:1 because it is a prediluted oil (contains solvents). Mobil 2T burns very clean at this ratio.
My experience with Amsoil which is not prediluted shows that mixing at anything richer that 50:1 leads to oil pooling in the muffler. Amsoil mixed at 50:1 and higher burns clean.

Sounds like solid proof to me. Do you lighten the ratio for other equipment Mike72 or run 32:1 Mobil 2T in everything?

Two cycle Lawn Boy mowers are the only power equipment I have. I've been running 32:1 Mobil 2T for two seasons now in a 7024 and a 8238. I take off the mufflers at the end of each mowing season to check the exhaust ports and for oil pooling. So far the ports are clean and no oil pooling. I ran a 5269 with 40:1 Amsoil a couple of years ago and posted the results with pictures on another forum. The next time I use Amsoil it will definitely be at 50:1 or higher.

I mix 32 to 1 on everything I run, which includes Lawn-Boys, Shindaiwas, Echos, Mantis (Echo), Stihls, and Sears two cycle equiptment. Most of the trimmers, saws, blowers, and tillers recomend 50 to 1 but they get and seem to like 32 to 1. I like to know that they will not lack for oil as replacements are expensive. I experiance no smoke after warm up and no oil dripping out the exhausts. One very important thing to remember about two-cycle engines is that "Quality of oil is Never a subsitute for Quantity of Oil" and "More Oil means More Power due to better ring seal and also more additives like detergents, anti-scuff agents, anti rust agents etc. Oil is the life blood of your engine, don't short it.

If in doubt I error toward the rich side, after all a little extra oil is cheaper than a new motor. On the other hand too much oil will hinder the fuels ability to cool the motor.Gasoline is cold to the touch and too much oil will lesson the cooling affect.

Stu, can you be more specific on how gasoline can "cool" an engine? Being cold to the touch? Once gasoline has vaporized before combustion in ANY gasoline engine, wether being drawn into the combustion chamber directly, or though a port or intake plenum, it's significantly higher than ambient temperature, so how would gasoline cool and engine? Oil and oil alone is the only cooling besides air flow or a liquid cooling system and engine will get. The only time you may get a slight cooling effect from fuel is before the engine reaches running temp. This is one reason diesel manufacturers went to indirect fuel injection, especially in the marine market. Squirting cool or near ambient fuel on hot piston domes creates more soot, whereas warmed fuel traveling through intakes give the fuel more time to vaporize and burn more efficiently. Gasoline is cool to the touch because of it's chemical composition and the acid bases used to break down the crude oil during blending. There is a retired "oil field" worker here that may be able to help you more with this topic.

It's not that complicated it just does, it's part of gasolines job.In a two stroker if you run a too small main jet you will have a lean condition making your motor heat up and it can seize, not enough fuel for cooling.Gasoline is always cold to the touch no matter what the outside temp. is, it's just always cold.Some higher compression motors require higher octane and are told to run at least 89 to help cool the motor.Now I don't know this but it sounds to me that if you took two thermometers and put one in reg. gas and the other in premium the premium will read colder.

Stu, when you "jet up" on a 2 stroke, it's usually because the engine as been opened up in someway to breathe better via intake upgrades, exhaust or both. When an engine is drawing more air, you need more fuel to support efficient combustion or the engine will run lean and possibly seize. The fuel is making optimum atomization when mixing with larger volumes of air-it's NOT cooling an engine! I've got a gallon of 30% nitomethane fuel 10 feet from me, mixed with 99% pure methanol and is cool in ambient temps but no more than a gallon of premium would be IF it were nearby, but it's not. Have you ever heard of "cold seizing" a 2 stroke? Very real condition that can happen from running a 2 stroke(usually snowmobile) at w.o.t. before the engine has warmed to temp, allowing the piston to expand and a much faster rate than the cylinder. Do you have anyting solid either in experience and or in scientific studies that can prove gasoline actually cools an engine significantly? Just want to know if your claims are personal ideas, or actual scientific fact. What kinds of tuning or racing experience do you have with 2 stroke engines? I'm always up for knowledge!

An example is the DuraForce engine.To lean from the factory caused the surge condition.Opening up the jets, which I learned from this site,cured the problem and at the same time because of the added fuel reduced the motors operating temp.I've never taken the exhaust temp. before I made the jetting change so I cannot say for sure but I bet it lowered the operating temp. of the motor a couple degrees.

That engine was made to run lean for EPA emission standards. 6.5 hp needed more air to make the hp. It also needed more fuel-we agree. The engine was jetted too lean which caused the surge, we agree. Did it over heat because it was not getting enough fuel to support the air volume the engine required to keep from surging or or it needed more fuel to cool the engine to keep it from surging? See the point? The engine surged because lack of fuel/air ratio. It wasn't a "surge" created from high heat in the combustion chamber to which you claim gasoline "cools" an engine, right?

I think stu is refering to the cooling effect of the gasoline as it vaporizes. All liquids absorb heat when they go into the vapor state. Because of this gasoline does cool an engine a certian amount.

Sure mike72, in the utmost scientific realm of physics, but by the time the fuel leaves it's supply(tank), and is vaporized either through carbureation or injection, it has already achieved a temperature higher than ambient surroundings either air or the inside the engine component/combustion chamber. The cooling affect of this would be so minute, that it wouldn't be able to be read or registered as "effective cooling". Cool dense air makes for more power and a smoother running engine usually, as we know. Fuel coolers used in the racing industry keeps alcohol blended fuels from heating too soon and vaporizing where it's needed, in the combustion chamber, not the intake manifold. Has no affect on engine cooling.

There is definitely a cooling effect.I don't know how much but there is.

Gasoline changing from the liquid state into a vapor will absorb a significant amount of heat, just keep in mind the relativly small amount of fuel being fed to an engine. In a 2 stroke the outside air and vaporizing fuel are the only things cooling bearings, the slight amount of oil migrating through the crankcase just lubes but is not enough to provide cooling as in a 4 stroke with oil splashing all over the place. Ask an old pilot about "carburetor icing" and that will give you an idea about the amount of heat vaporizing gasoline will absorb.

Lean fuel/air mixtures in 2-stroke engines do indeed create higher engine temperatures and richer fuel/air ratios create cooler engine temperatures.
Here's how that works. A very crude comparison to something most of us are familiar with....An open flame on an acetylene gas torch is a good example. Turn on the oxygen and acetylene and light. A mal-adjusted torch produces a bright yellow or orange smokey flame that is very cool in welding torch circles and will not accomplish much more than lighting a trash pile. Very inefficient. That scenario represents an overly rich mixture in the Lawn-Boy. Low power, smokey, inefficient. The properly adjusted torch yields a blue flame than is thousands of degrees hotter than the previous yellow torch. Efficient, no smoke, and very, very hot. Engines cannot run at high temperatures like a cutting cutting torch or even close so the engineers jet the carburetors to get the most efficient clean burning mixture without reaching astronomical temperatures. The blue flame torch represents the lean mixture Lawn-Boy. Cleaner, more efficient, and hotter. So that's a round about way of explaining how a lean engine burns hotter and a rich engine burns cooler. Combustion temperature is directly related to fuel/air ratio. A Duraforce was designed to run leaner and has more cooling fins than an "F" engine so it can handle the higher temperatures of the lean fuel/air ratios.

echoman, the laws of physics govern the operation of a carburetor and they are not considered to be in the "utmost scientific realm", they are basic laws. Gasoline absorbs heat when it goes into vapor and also the air that is expanding after passing through the venturi also absorbs some heat. In most engines the carburetor is attached to a manifold where the cooling takes place. On a two stroke Lawn Boy the carburetor is attached directly to the crankcase and the cooling takes place inside the engine. On many engines especially aircraft, this cooling can be so great as to cause ice to form on the throttle plate or inside the intake manifold, it depends on outside air temperature and humidity. These engines are usually equipped with intake air pre-heaters to prevent this.I agree that in a Lawn Boy engine this effect is not great but it is there nonetheless.

There are several people here with facts, but I think nobody has everything exactly right. I hope I can add some clarity.

As for oil, I believe its primary cooling ability would be from reducing friction. Since it doesn't vaporize until actual combustion (at least the best oils do), then it can't cool the engine by absorbing heat in a vaporization process.

Gasoline in liquid form will reach ambient temperature. IOW, like any substance that remains liquid at ambient temps it will reach equilibrium with the outside air. So you can put a thermometer in a gallon of gas but it won't be any cooler than the outside air in which it's been stored. The reason it feels cool on your skin sometimes, I'm sure, is because it is evaporating (probably parts of it, while some components of it get left behind). That's a vaporization process, and just like water that's drying off of you it will cool your skin.

So that brings us to gasoline and vaporization. Yes, gasoline does have a cooling effect as it vaporizes in the carburetor. Since it's not the most complete vaporization in the venturi of the carb, I _think_ it probably keeps vaporizing as it enters the hot crankcase and chamber and keeps absorbing heat until it is really well vaporized. I can't put a number on it, but it is going to correlate to gasoline's specific gravity (and different blends have different SGs, to the point that one way they test racing gas to see if a driver cheater is to test the SG of whatever is in his tank) and the amount of fuel being vaporized. It is significant, and you can see this by looking at the new direct-fuel-injection cars coming out from Audi/VW and soon Cadillac and others. They are suddenly getting away with much higher compression ratios in those cars: 12:1 for a naturally aspirated VW and 10.3:1 for my _turbocharged_ VW, for instance. That is almost entirely due to charge cooling from the injected gasoline's fast vaporization. I find it hard to believe that varying the oil ratio would significantly affect the cooling from vaporization unless we are talking about some ridiculously high ratio of oil (like below 10:1), but I'd be open to data showing otherwise. Likewise, I'd be surprised to see a big decrease in cooling from a reduction of friction unless we are talking about really high oil ratios. And I think at that point you would have real wear to worry about from high friction - i.e., the heat and friction will be taking their toll on the engine together. I'd think the cheaper engines with plain bearings would be more susceptible than good engines with full ball bearings. Again, I'm open to being proven wrong (i.e., learning).

But one thing that isn't true is that carb icing in a plane is mainly due to cooling from gasoline's vaporization. I'm sure it contributes a little, but the main reason for it is the rapid acceleration of intake air through the venturi of the carb. That also causes cooling and concurrantly lowers the air pressure such that humidity in the air condenses. Normally it's no big deal, but if the conditions are cold enough and wet enough that condensation will freeze. This could happen on a car or any carbureted engine, but it's more likely in a plane due to the conditions in which they fly.

As for combustion temps and air:fuel ratios, it is true that leaner is hotter up to a point. If the total exhaust temp goes up as you lean out an engine, then you must be making more power. So up to a point leaning an engine out isn't bad. I _think_ the damage comes from incomplete combustion that creates hot spots with overly lean settings. At that point, only part of the exhaust is hotter, and the total exhaust probably come down but certain parts of the chamber and piston get too hot. This would also correspond to less power output and erratic running (surge, anyone?). Going back to piston aviation engines, most have manual mixture controls that a pilot can adjust in flight. It is routine and spelled out in most operating manuals that for best economy (but not best power) the pilot should actually lean out the mixture 50* lean of peak exhaust temperature. This is considered safe, but if the pilot wants full power (which is only achievable at lower altitudes, btw) then he would need a richer mixture for safety and power.

I think I hit all the highlights, and I hope this is helpful.