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#482328 - 09/27/03 11:40 PM 2 cycle pre-mix oil
Blue99 Offline


Registered: 09/27/03
Posts: 2233
Loc: Wisconsin
The 2 cycle pre-mix ratios for air cooled engines changed in the 70s 80s from 32:1 to 40:1 ratios. Now days, the standard is probably 50:1 (if Amsoil products are excluded).

What were the technological advances in either base stocks or additives that enabled the smaller volume of pre-mix to be added to a gallon of gas?

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#482329 - 09/28/03 12:47 AM Re: 2 cycle pre-mix oil
blano Offline


Registered: 12/24/02
Posts: 687
Loc: Canada
Mixture ratios for two cycle engines is largely driven by the epa and the fear they cause the mfgs. Two cycle oil tech has changed alot since the seventies mostly in the area of cleanliness and lack of smoke although this excludes the oem oil standard oils IE stihl, mac, tanaka, etc) as they are still formulated to circa 70 api tc specs.
While I do not know for sure amsoil 100:1 I bet they use a really high temp basestock and a hearty dose of mettalic adds to make a 100:1 ratio work ok. Porblem with thi strategy is the fact that both high temp base oil and mettalic adds lead to deposit problems.

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#482330 - 09/28/03 01:36 AM Re: 2 cycle pre-mix oil
labman Offline


Registered: 03/14/03
Posts: 8711
Loc: Nothern USA
So what happens when I put a modern oil in my old 16:1 Poulon? I have heard it is very important to use the right mixture.

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#482331 - 09/28/03 02:49 AM Re: 2 cycle pre-mix oil
Blue99 Offline


Registered: 09/27/03
Posts: 2233
Loc: Wisconsin
Labman Im a newbie to this site, but I can respond to your question. My Remington SL9 chainsaw is early 70s and lists a 16:1 pre-mix ratio. On the inside of the air filter cover it states Mix ratio 16:1 using SAE 30 2 cycle oil.
I mix any API-TC air cooled pre-mix oil at 32:1 which is 4 oz. to 1 gallon. A 16:1 ratio would require 8 oz. dumped into 1 gallon of gas (a lot of pre-mix). From a practical point, 8 oz. of pre-mix will cause the equipment to smoke & buildup carbon in the exhaust port and muffler.

And this is what we are discussing. The formulation of commonly sold 2 cycle pre-mixes has changed over the years & were trying to define the specifics.

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#482332 - 09/28/03 03:32 AM Re: 2 cycle pre-mix oil
Blue99 Offline


Registered: 09/27/03
Posts: 2233
Loc: Wisconsin
Blano- I guess the issue is have changes in the commonly used API group1 petroleum base stocks allowed the amount of pre-mix to change from 4 oz (32:1) to 3.2 oz (40:1) ?

Has the viscosity index of the commonly used base stocks moved to the upper end of the API range of 80-119? This would improve volatility and more of the pre-mix oil would make it to the combustion chamber to lubricate the cylinder walls & piston rings.

Or have the base stocks remained the same formulation & it is an issue of % of solvent and additives?

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#482333 - 09/28/03 10:21 PM Re: 2 cycle pre-mix oil
TooSlick Offline


Registered: 08/02/02
Posts: 5785
Loc: Dixie
Ben,

I'm still trying to figure out this mix ratio stuff ....

Is your goal to run the richest mixture ratio you can, to maximize compression and still get clean burning? It would seem to me as a engineer that for a particular oil and application, there would be a mix ratio that is the best compromise of:

1) subjective engine performance
2) wear protection
3) deposit formation
4) plug fouling
5) exhaust smoke
6) fuel octane degradation

If I was testing a new two stoke oil, I guess I'd start at the oil manufacturers recommended mix ratio and do some testing on either side of that ratio. Am I missing something here???? [Frown]

TS

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#482334 - 09/29/03 04:53 AM Re: 2 cycle pre-mix oil
blano Offline


Registered: 12/24/02
Posts: 687
Loc: Canada
"Is your goal to run the richest mixture ratio you can, to maximize compression and still get clean burning?"
Too slick, To answer your question, yes! A good oil will burn clean at 32:1, protect better under extreme conditions, and leave an engine cleaner than these 100:1 wonder lubes. Keep in mind that 50:1 and leaner ratios are a product of the epa and public perception. A case in point is stihl chain saws. The basic engine designs of these saws hasnt changed since the late seventies when a 32:1 ratio was reccomended. Today a 50:1 oil ratio is reccomended and the oil that stihl sells hadnt changed much until last year when they came out with a iso egd jaso fc oil and labeled it as a premium product while still selling there circa 1979 formulation orange bottle oil. My point being is that stihl changed their oils reccomendations not because of any new tech, but because of other concerns. More oil is better and this can be easily recognized by pokeing ones head into the pits at a shifter cart or national mx race. .

[ September 29, 2003, 08:09 PM: Message edited by: blano ]

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#482335 - 09/29/03 05:59 AM Re: 2 cycle pre-mix oil
TooSlick Offline


Registered: 08/02/02
Posts: 5785
Loc: Dixie
Blano,

What about engines that use oil injection ....It is my understanding that these are calibrated to run mixtures of 100:1 at idle, up to about 50:1 at full throttle. Do you tinker with the oil pump output on these as well? I am specifically talking about sleds and PWC's ....

TS

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#482336 - 09/29/03 06:28 AM Re: 2 cycle pre-mix oil
blano Offline


Registered: 12/24/02
Posts: 687
Loc: Canada
"Do you tinker with the oil pump output on these as well?"
Yes, although not on all sleds as some pump a exceptable amount. For instance my 98 xcr 440 used a little bit more than a quart of oil per ten gallons of gas. This is right around a 32:1 ratio. My 97 polaris xc 700 with a big bore kitted motor however used less than a quart per ten gallons till I turned up the oiler. I try to shoot for 32:1 as it seems to work well in most motors. I have ran as rich as 18:1 (125 mx bike that was ice raced) in certain applications where I was reving the heck out of the motor in high load conditions. BTW I beleive polaris oil injection pumps are suppose to pump 40:1 at wide open throttle. I would just ditch the injection sytems altogether if it where not for the fact the Polaris injects oil directly into each crank bearing. Good system IMO.

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#482337 - 10/02/03 07:28 AM Re: 2 cycle pre-mix oil
Cujet Offline


Registered: 02/15/03
Posts: 4124
Loc: Jupiter, Florida
Another thought, If you are looking for maximum power out of your 2 stroke powered device. The best bet is to go with a 16 to 1 ratio. Testing I have done for race teams in the past show that more oil makes more power. As a matter of fact, using more quality synthetic oil will keep the small engine cleaner. I know many believe otherwise, however be my guest and try it for yourself, you will be convinced. Ratio's (using synthetic)such as 8 to 1 will keep an engine perfectly clean internally.

Chris

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#482338 - 10/02/03 08:19 PM Re: 2 cycle pre-mix oil
Blue99 Offline


Registered: 09/27/03
Posts: 2233
Loc: Wisconsin
Cujet,

The di-ester 2 cycle pre-mix synthetics are reported to have the ability to dissolve deposits, tarnish and carbon in the cylinder & crankcase. From your testing, it sounds like the product could also be promoted as "Merry Maids in a Bottle".

Regarding the mix ratios in your racing testing,(more power from more mix in the gas), I'm assuming this is with synthetics. At 16:1, when you do a tear down, do you find an accumulation of synthetic in the crankcase? If not, then my thoughts are that the surface temp of the crank pulls only a set amount of ester base out of the gas & the rest is ported into the cylinder to lubricate or be combusted.

Also, at 16:1, does running the engine at idle create any problems with plug fouling? This is probably more of an issue with chainsaws, trimmers & leaf blowers than with racing engines.

Thanks for relating your testing results.

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#482339 - 10/02/03 08:39 PM Re: 2 cycle pre-mix oil
Kestas Offline



Registered: 06/04/02
Posts: 10805
Loc: The Motor City
I have three small 2-cycle motors that each use a different mix - 16:1, 32:1 and 40:1. I keep a separated stash of mix for each motor.

I'm still confused on what everyone is saying. Am I correct in saying that these different ratios aren't needed for each motor?... that these ratios are specified not for technical reasons but for different agendas each manufacturer has for their product.

I'd like to simplify my stash of mix and do what's best for my equipment. Would it be okay if I used 32:1 for ALL of my small 2-cycle motors, regardless of specification?

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#482340 - 10/02/03 08:40 PM Re: 2 cycle pre-mix oil
Cujet Offline


Registered: 02/15/03
Posts: 4124
Loc: Jupiter, Florida
Blue, our testing was with Mercury outboard engines. As such, we did not have the ability to pull the cylinders off and look inside the crankcase. I suspect the level of residual oil in the outboard remains the same no matter what the ratio.

We did test with synthetics and that wonderful oil provided for free by the factory (non synthetic). For racing use, we chose the free stuff. However there is no question that the synthetic was a better oil. Even so, both oils left near zero deposits when used at an 8 to 1 ratio, especially the synthetics.

Chris

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#482341 - 10/02/03 08:43 PM Re: 2 cycle pre-mix oil
Cujet Offline


Registered: 02/15/03
Posts: 4124
Loc: Jupiter, Florida
Kestas, 32 to 1 is the old standard. Use a good quality oil and I am convinced you could do no better. High oil ratio's have not (in my experience) extended engine life one bit.

Chris

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#482342 - 10/03/03 06:09 AM Re: 2 cycle pre-mix oil
blano Offline


Registered: 12/24/02
Posts: 687
Loc: Canada
"If not, then my thoughts are that the surface temp of the crank pulls only a set amount of ester base out of the gas & the rest is ported into the cylinder to lubricate or be combusted."

Blue, This isnt the case. In order for a two cycle oil to lube it has to come out of suspension when it reaches the crank case. Its quit simple actually. The fuel enters the crank case in a liquid state(ie small droplets). The heat of the crank case at operating temps evaporates these droplets very rapidly causing the oil to drop out of suspension and coat all internal parts. This happens with oil oils, syn or otherwise. A example of this is not occuring is when the motor is first started. Since the crank case is not yet warm the fuel doesnt evaporate and the oil doesnt drop out of suspension. Instead sent directly to the combustion chamber where it partially burns. This unburnt oil is what causes smoke on startup. BTW There are many oils that use ester bases that are not di esters. polyol(redline) and carboxl(mx2t) are two of the most common.

[ October 03, 2003, 09:18 PM: Message edited by: blano ]

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