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.

Normally, I'd be quite critical of someone hauling an old thread out of the archives and reviving it but your post does fit into the spirit in which this thread began. Ask an Ingersoll dealer and they will tell you about the customer loyalty they enjoy thanks to the durability that is built into every one of these garden tractors. I am not being critical when I say that there is nothing all that unique about your 19 years of experience with your GT. When John (Jack) Ingersoll bought the Outdoor Power Equipment Division belonging to J. I. Case and put his name on it, the slogans used in their advertising went as follows: - Quality in the American tradition - Be in a class by yourself - Ingersoll...Invest in the best - The tractor of a lifetime I would have to say that your experience proves that the above slogans were not an exaggeration in any way. I don't know of another tractor today that uses hydraulic drive, offers a large line of hydraulically powered attachments or still builds their garden tractors without compromise. You invested in the best and it paid off in spades because after 19 years of hard use, you still own a tractor that has value to others. If you amortize what you paid for your tractor over the 19 year period and include the cost of replacement parts, the annual cost of ownership of this fine quality machine is very low. The other bonus is the absence of the aggravation factor that comes with owing an Ingersoll. When other people are having to take the time needed to send their low quality machine in for repair and then pick it up, your Ingersoll was at home and ready to do some more work for you. A "generation" occurs every 20 years and to some, that is a lifetime. Your tractor is still far from being dead even after 19 years so Jack Ingersoll wasn't lying when he said his products were "the tractor of a lifetime". Thanks for providing your first-hand report about a marque that few people have heard of but still "makes them like they used to", only better.

Fixed it - yippeeeeeeeeeeeee Not sure which bit was not playing ball but this afternoon I've: -Adjusted the valve clearances (they weren't out by much but are now spot on) -Cleaned completely the petrol pump and blown through with an airgun. -Added a new in-line petrol filter -Re-cleaned the carb - took everything apart - washed and cleaned in neat petrol, used an airgun and blow dried everything and pushed fishing line wire into every hole I could find. I've completed a test cut of 40cm high grass in one of my paddocks (way higher than I usually cut with this tractor) and power was definately back to as it should have been and managed to wade through the grass cutting as we went without the engine dying on me. Yesterday it would have struggled to cut 10cm high grass and would have probably died several times in the process. Many thanks to all for your help and advice and the links to the papers (all printed out and in the file) and hope this post is useful to someone else later on. Off to fix the 4x4 now....

Hello Marco, I hope your project is coming along well. I have had two Wheel Horse tractors with Sundstrand transaxels. The first was 14 years old when I got it. My Current tractor is a Wheel Horse Charger made in 1969. Both are 100% reliable. These tractors use a single forward/reverse lever control located just to the right of the steering wheel. No "cruise control" is required as the lever will stay where you put it. The tractor can be stopped by returning the lever to the middle position. There is a foot pedal that can do this. I find this very handy. The foot pedal on these tractors is on the left, Familar to me since I grew up driving a WH suburban manual with the combined clutch/brake on the left. But probably this should be on the right for optimal ergonomics. I agree with others who say that hydro is the way to go 100%. When mowing not only is it good when you need to back up or manuver, it is also very good for when you hit a thick patch of grass or have to slow down to negotiate a slope. I also use a dozer balde/snow plow and having the ability to go from forward to reverse to forward is really nice. The only real disadvantages I am aware of is the fact that hydros use more gas, and cost more. So, if you can improve the efficiency that would be good. Or maybe reduce complexity or weight. The other thing I like with the Sundstrand is they have ports for other hydraulic attachements. I wish the were brought out to some sort of common fitting (or quick fit) so that adding accessories would be a matter of modular connections versus having to remove plugs, add shimes, etc to use this feature.