What kind of gas wont hurt my 70cc engine and works best?

[Steve]

Drew,

I was told the "W" in TCW is an abbreviation for water cooled, and that oil is designed to run in water cooled engine which run significantly cooler than our air cooled engines. I was told that by another engineer.

DrewD,

that's some really good info, thanks

my lead substitute question (a runover from my V-8 gearhead days) is stoopid i guess? these engines won't benefit from the "lubricating/coating/cushioning" effect?

TCW oils: This is an industry developed specification used for outboard marine engines and was specced for "low revving" engines that run cooler temps than air-cooled non-marine engines.

The correct oil to use for a 2 stroke air cooled oil is: API-TC but this specification has not been changed since 1993 and this oil is very hard to find though required by certain 2 stroke engine makers such as bombardier. In fact, Bombardier and Rotax are the only ones who make a 2 stroke oil that is API-TC certified. Many other 2 stroke oils may meet this standard and TCW standard too but they aren't certified that they do and don't display it on their label. Certification to an API standard can easily run into 6 figures for a company.

Now with that said, today's marine engines rev much higher than yesterday's engine and generate more HP then previous verions. Also, many engine makers recommend TCW oils for all of their 2 strokes regardless if they are water cooled or air cooled. Given that TCW has been changed

Here is why I believe we are ok using TCW in our 2 strokes:
1. We are running at a 20-32:1 mixture ratio.
2. If our engines were very high tech and high revving than TCW oil wouldn't be the best thing for it. However, I doubt our 70/80cc engines ever see 10k rpm under load. Let's face it, these chinese 2 strokes don't generator a lot of power for their size. They are restricted by intake, exhaust, stroke and port timing to be very mild.
3. Due to emission reasons, many makers have to recommend a 50-100:1 oil ratio for their engines. A higher quality oil is needed but a lower quality oil at greater ratios should suffice.

With that said, the actual best oil standard is from Europe: It is ISO-L-EGB which tests an oil at a 150:1 ratio in an engine for 3 hours run and then measures various criteria. TCWIII and API-TC oils are tested under a 1 hour interval.

If these chinese engines were a big investment, then go for it and use the better quality oil but for 99.9% of us, TCWIII at such high ratios is sufficent.

I'll let you know how my 3rd bike holds up. I'm milling the head to up the compression ratio and running a mixture that is 80% gasoline (50:1 fuelil ratio) with remainder being 25% methanol mix that contains 20% nitromethane and 18% blend of castor oil and synthetic 2 stroke oil. I live at high altitude and my carb is too rich on regular gasoline. This blend of fuels has been used for past year on my two other bikes with no ill effects and the power is much better at altitude than stock-it doesn't run as rich as before and actually rev's where it should.
If I don't get desired performance with this mix, I'm going to get the grinder out and see if I can alter the port timing which I suspect is very conservative.

Oh, forgot to mention. Way back when, many 2 stroke lawnmower engines (similar low tech stuff in our engines) could be run on either #1 diesel (similar to kerosene) or gasoline. The reason is that the engines, like ours, have a ridiculously low compression ratio and using a low octane fuel such as kerosene didn't cause detonation.

You could probably get away with using kerosene if you had too as long as it wasn't too hot outside.

well! i just refueled last night, went with the cheap stuff.

today, it's starting even better than before & idles way down very nicely.

...and maybe it's just me but it sure feels like it has bit more "scoot" to it, thanks DrewD 8)

[Steve]

Not really cheap stuff, but low grade anyway, we use Coleman Camper fuel in our radio control helicopter two stroke gasoline engines (a copy of a small weedeater engine 23 cc), and they run just fine. Camper fuel is sometimes called white gas, is rated somewhere around 55 octane, and the reason we use it is it burns super clean and has no strong gasoline odor. You can open one of these engine after having run many gallons of the camper fuel and there will be absolutely zero carbon. The fact it has no odor allows us to transport them in vehicles and store them in the house with no foul gasoline smell. The bad news....it costs about $4 a gallon.

[sherryc8641]

Thanks for all of the good info

[mrsaxman99]

Originally Posted by Steve

Not really cheap stuff, but low grade anyway, we use Coleman Camper fuel in our radio control helicopter two stroke gasoline engines (a copy of a small weedeater engine 23 cc), and they run just fine. Camper fuel is sometimes called white gas, is rated somewhere around 55 octane, and the reason we use it is it burns super clean and has no strong gasoline odor. You can open one of these engine after having run many gallons of the camper fuel and there will be absolutely zero carbon. The fact it has no odor allows us to transport them in vehicles and store them in the house with no foul gasoline smell. The bad news....it costs about $4 a gallon.

do you worry about the superfast burn cycle casuing any detonation?

[Steve]

Originally Posted by mrsaxman99

do you worry about the superfast burn cycle casuing any detonation?

No, it has caused no problems and there are lots of people running it in lots of engines.

[jaker]

i remember reading about this when i rode dirtbikes all the time seems there was even an article in a dirtbike magazine i had stating how in mexico the gas is low octane but its actually better for a 2 stroke than the good stuff..

consider this, the average car has a 9 to one compression ratio were using like 6 to one so low octane is our friend