This question is around my riding mower, hopefully it is still relevant here. I recently had my tractor serviced and shortly after it was serviced it would not start. So I called the company back out and his notes stated that the tractor had gas in the oil and he had to drain the oil and replace solenoid /gas filter/oil filter, oil. He then charged me approximately $300, parts 100/labor 200. The tractor worked for a couple of weeks and then would start again. I would crank the engine and it would just grind and spray gas all over the floor. I eventually managed to get it started and started cutting the grass and then after two or three lengths of the yard it then cut out and smoke was billowing out of it. So I called him back out and he said gas was in the oil again and drained the oil again, changed the spark plug, changed the oil filter and charged me $45 in parts and 125 in labor.

I phoned him up to complain and he said all my problems are being caused by the fact that I use 87 gas, he said that this was a major problem this year and that all mower companies are experiencing problems such as this. I have used 87 since I bought the tractor 5 years ago and never had a problem. I would not imagine that using 87 could somehow cause the oil and gas to mix together. Is there anything to what he is saying or is he just ripping me off?

Kevin, July 2009

no matter what octane fuel you are using it won`t cause fuel in the oil !!!!
You either have a bad fuel pump or the needle and seat in your carb is leaking ......either way this condition will burn your engine up or cause a fire ...yep I would say your getting ripped off

bg, August 2009

Er....I think Mickey-G is drinking the gas.....

87 octane fuel is perfect for running a mower on. Most of the world uses 95 to 98 octane fuel, as the liquid cheese that passes for fuel in the States is not available elsewhere.

In addition, a hotter plug will cause pre-ignition due to the reduced anti-knock properties of lower octane fuel (that's what the octane rating means - higher numbers = more knock resistance).

If you really want to use a lower octane fuel, put in another head gasket (meaning fit 2), and run on kerosene (yes, I am serious). You would need to rig a duel-fuel tank, so that you start up and shut down on gas, and run on kero. Some older Briggs engines were built this way.

In answer to your original question, yes you are being ripped off. Assuming the original diagnosis of fuel in the oil is correct, the problem needs to be fixed, not simply masked by replacing the oil and filter umpteen times and charging for labour each time. I think John has it right with point '1' in his answer.

phil_saunders(a)bigfoot.com

Phil Saunders, July 2009

Sir: you most certinally are not being riped off by the repair mechanic: an 87 percent octain gas will eventually cause the rings to burn out and that is what is allowing the gas to get into the oil. you need to replace the rings and go to a lesser octain gas and a hoter spark plug.
this will fix your problem 4 cycle engines are not designed to run on high octain gas. you should go to something like 82 percent octain gas.
Hope this is of help to you.

Mickey-G, July 2009

Hi Kevin
There are two ways that fuel can enter the crankcase, to dilute the engine oil.
1) If your machine has a mechanical fuel pump on the side of the engine, a diaphragm seal failure here will cause this (although I've never come across a ride on with this system)
2) If the carburettor is constantly flooding, say overnight, its just about feasible that fuel could flow down past the inlet valve, bypass the piston and enter the sump.
The quality of the fuel is irrelevant to your problem. I guess you are referring to the octane rating? Over here our minimum octane rating is 95. Either way, your 'mechanic' is talking rubbish. So - dip the oil level after you have used the machine. Dip it again in the morning to see if the level has risen. If there is a petrol tap in the fuel line its a good idea to turn it off when the machine is out of use.

John, July 2009