Oil mixture ratio charts

[jspriddy]

To all who feel this has been beaten to death and are sick of reading of it, please feel free to move on. I have done searches here and found nothing that really addresses this particular issue.

While preparing premix for my outboard, which is recommended to run a 100:1 mix, I looked on the 2-cycle oil bottle and it said 2 ounces for each gallon of gas. I did a little quick math in my head, and thought that this didn't sound right. Turns out, 2 oz. per gallon is actually 64:1. I would assume when an engine manufacturer says 100:1, they actually mean 100:1, which would be 1.28 oz. per gallon, or 2 1/2 oz. for 2 gallons, etc.

I certainly don't want my engine to be starved for oil, but on the other hand, I don't want to be fouling plugs every other day.

Any thoughts?

Thanks,

John

 

[Chris1956]

John, A couple of things. Manufacturers do round off the oil to make the math easy, but not to the extent your are seeing. For example, a nominal 50::1 mix is 1 pint (16oz) oil to 6 gal of gasoline. If you do the math, it is really 48::1.

Secondly, most 2 cycle motors call for a 50::1 mix. You might doublecheck your motor's requirements. Some OMC motors called for 100::1 when manufactured, but that was later changed to be 50::1.

 

[Sea Rider]

50:1 is around 80 ML per 1 (3.78) US gal. 100:1 is 40 ML per galon. Check specs if liking running at full throttle on a constat basis. 2 stroke OB's don't like running at slow idle/throlling speeds for extended time periods if with 50:1. Besides those slow speeds, not an issue on the rest of the power band.

Happy Boating

 

[jspriddy]

John, A couple of things. Manufacturers do round off the oil to make the math easy, but not to the extent your are seeing. For example, a nominal 50::1 mix is 1 pint (16oz) oil to 6 gal of gasoline. If you do the math, it is really 48::1.

Secondly, most 2 cycle motors call for a 50::1 mix. You might doublecheck your motor's requirements. Some OMC motors called for 100::1 when manufactured, but that was later changed to be 50::1.

It was a chart-X number oz/ X gallons, and as the total amount of fuel increased, the ratio got much closer to what it was actually supposed to be. You're right-at 6 gallons it's very close. But I was mixing just one gallon to run it just a few minutes before winter and it struck me how much it was off at that low amount. By the way, I went ahead and mixed it at the 2 oz per gallon just because it hadn't been run in a while, and might be a while again. I wouldn't have done it for normal use, however.


My engine is a 1994 Yamaha 25 hp 2 cylinder. Everything I find says 100:1. If any change to the recommendation has been made, I'm unaware of it. I suppose I could contact Yamaha.

Thanks,

John

 

[jspriddy]

50:1 is around 80 ML per 1 (3.78) US gal. 100:1 is 40 ML per galon. Check specs if liking running at full throttle on a constat basis. 2 stroke OB's don't like running at slow idle/throlling speeds for extended time periods if with 50:1. Besides those slow speeds, not an issue on the rest of the power band.

Happy Boating

Thanks. I usually split the difference and run about 75/80:1, since I never know how I'll be running.

John

 

[Fun Times]

Looking around, Yamahas 28 HP and less calls for 100:1 but a lot of people that switched to 50;1 has done so successfully.

25HP Owner's Manual - Yamaha Page 22 & 24.

 

[JimS123]

Looking around, Yamahas 28 HP and less calls for 100:1 but a lot of people that switched to 50;1 has done so successfully.

25HP Owner's Manual - Yamaha Page 22 & 24.

My Yamaha also calls for 100:1. I switched to 50:1 because some expert on here said it should be run at 50:1 or risk engine damage. It smoked like crazy, even when running synthetic.

I now run 100:1 because that's what Yamaha says and the motor runs much better now.

 

[Fed]

Got me beat why the US persists with those funny old units... GO METRIC!

 

[gm280]

Actually jspriddy, if you are really technically serious about ratio mixtures, 1.28ozs of oil to a gallon of fuel is not a 100:1 ratio it is really 101:1 mixture. That would be 1.28oz of oil to 128.0ozs of fuel for a new mixture of 129.28:1.28 mixture. Because you add that 1.28ozs and therefore the exact mixture is now changed. I realize that is splitting hairs, but that just shows how rough the mixtures we mix up and use. For a 50:1 mixture we normally pour 16ozs oil into 6 gallons of fuel. But that isn't 50:1 either, it is 49:1 to be exact. I don't think anybody really cares to make their mixtures that seriously accurate. But it shows how inaccurate we all mix our oils and fuels...

 

[jspriddy]

Looking around, Yamahas 28 HP and less calls for 100:1 but a lot of people that switched to 50;1 has done so successfully.

25HP Owner's Manual - Yamaha Page 22 & 24.

There's been all kinds of arguments here and elsewhere (mostly the coffee shop where I eat breakfast) about the 50:1 vs. 100:1 mixes. As I said, I try to run somewhere in the 75-80:1 range. Sorta like covering all your bases, so to speak.

And many thanks for the link to the Yamaha manual. I'd been looking for that.

Again, thanks,

John

 

[jspriddy]

My Yamaha also calls for 100:1. I switched to 50:1 because some expert on here said it should be run at 50:1 or risk engine damage. It smoked like crazy, even when running synthetic.

I now run 100:1 because that's what Yamaha says and the motor runs much better now.

I kinda figure Yamaha would have a vested interest in recommending what was best. Someone in another thread suggested they recommended 100:1 so you'd burn your engine up and have to buy another. I think they're smart enough to know you'd probably buy another brand, right?

Thanks,

John

 

[jspriddy]

Got me beat why the US persists with those funny old units... GO METRIC!

Well, maybe we're just traditionalists. I don't like designated hitters, either.

John

 

[jspriddy]

Actually jspriddy, if you are really technically serious about ratio mixtures, 1.28ozs of oil to a gallon of fuel is not a 100:1 ratio it is really 101:1 mixture. That would be 1.28oz of oil to 128.0ozs of fuel for a new mixture of 129.28:1.28 mixture. Because you add that 1.28ozs and therefore the exact mixture is now changed. I realize that is splitting hairs, but that just shows how rough the mixtures we mix up and use. For a 50:1 mixture we normally pour 16ozs oil into 6 gallons of fuel. But that isn't 50:1 either, it is 49:1 to be exact. I don't think anybody really cares to make their mixtures that seriously accurate. But it shows how inaccurate we all mix our oils and fuels...

You have to think of it as 100 parts to 1 part, and yes, that makes a total of 101 parts. But, wouldn't the mix still be 100:1? I see your point though, and realize my question was splitting hairs, but IF you were mixing just one gallon for whatever reason, the chart on the oil container was way off.

As Chris pointed out, once you reach the 6 gallon mark, it's close enough for government work at least.

Thanks for your input,

John

 

[Fed]

Well, maybe we're just traditionalists. I don't like designated hitters, either.

John

I'm all for tradition but after spending half a life with Imperial & half a life with Metric I have to say Metric is much better.
My curiosity got the better of me so I resorted to Google to see who uses what, a very surprising result and a good read as well.
http://www.zmescience.com/other/map-of-countries-officially-not-using-the-metric-system/

Down here in Oz we drive on the left side of the road I'd love to see us change to your side so we could get better cars.LOL
I believe there was a country in Europe that did the left / right change over a weekend and as far as I know they survived it.

All interesting stuff, I only found out at iboats a few years ago that America and a handful of other areas use reverse colours in there navigation markers.

Designated hitters?

 

[jspriddy]

I'm all for tradition but after spending half a life with Imperial & half a life with Metric I have to say Metric is much better.
My curiosity got the better of me so I resorted to Google to see who uses what, a very surprising result and a good read as well.
http://www.zmescience.com/other/map-...metric-system/

Down here in Oz we drive on the left side of the road I'd love to see us change to your side so we could get better cars.LOL
I believe there was a country in Europe that did the left / right change over a weekend and as far as I know they survived it.

All interesting stuff, I only found out at iboats a few years ago that America and a handful of other areas use reverse colours in there navigation markers.

Designated hitters?

That link was interesting. I had no idea so few (3?) used the Imperial system of measures.

"Designated hitter" is a baseball term. A "designated hitter" can take the place of the pitcher in the batting lineup, but only the pitcher. All other position players must bat for themselves. American League has it, the National League does not.

John

ps: Go Cubs.

 

[Frank Acampora]

What no one here has mentioned is that roller and needle bearings are very tolerant as long as there is no dirt. 100 to 1 is quite acceptable for lubricating purposes. OMC DID specify 100 to 1 a few tears ago but found the it did not leave enough residual oil in the engine parts to prevent corrosion upon extended storage. They switched back to specifying 50-1. I believe that on their oil injection systems, the amount of oil varies from 100 to 1 at idle to 50 to 1 at wide open throttle. 50-1 has been around since roller and needle bearings were introduced on outboard engines and very few people have had problems with this ratio mix.

Now, If Yamaha is specifying 100 to 1, then they either don't have a storage problem or have solved it. I might run the engine at 100 to 1 but if I intended storing it for a while I would be safe and run it on a rich 50-1 mix for a tank.

 

[JimS123]

Got me beat why the US persists with those funny old units... GO METRIC!

Fifty parts to 1 part is neither Metric or English. It's merely a ratio.

When I was in Grammar School we had to learn Metric because the US was going to switch "soon". That was 60 years ago. It has always made sense, but has been delayed over and over because the old fogie politicians can't do rithmatik.

 

[JimS123]

I try to run somewhere in the 75-80:1 range. Sorta like covering all your bases, so to speak.

,

John

That's what I thought too. Still smoked too much.

 

[jspriddy]

What no one here has mentioned is that roller and needle bearings are very tolerant as long as there is no dirt. 100 to 1 is quite acceptable for lubricating purposes. OMC DID specify 100 to 1 a few tears ago but found the it did not leave enough residual oil in the engine parts to prevent corrosion upon extended storage. They switched back to specifying 50-1. I believe that on their oil injection systems, the amount of oil varies from 100 to 1 at idle to 50 to 1 at wide open throttle. 50-1 has been around since roller and needle bearings were introduced on outboard engines and very few people have had problems with this ratio mix.

Now, If Yamaha is specifying 100 to 1, then they either don't have a storage problem or have solved it. I might run the engine at 100 to 1 but if I intended storing it for a while I would be safe and run it on a rich 50-1 mix for a tank.

I see your point. Even if someone has had a problem with 100:1, I don't see how they could definitely attribute to the oil mix. Any number of things could cause an engine failure. I suppose if the engine was torn down and rusted internally, that would be indicative of failure due to corrosion.

Do you think it would take a whole tank to coat everything internally?

 

[Sea Rider]

Is 100:1 rated for Yam Recreational OB's or for Commercial (Enduros) as well. We have tons of Yam enduro models in use, but for those Yam recommends 50:1, probably to be in the safe side of the equation and avoid premature repairs ?

Happy Boating