What ratio of oil and gas if I'm premixing?

[Jnkyrdg04]

89 marathon with a 3pg. Previous owner said the guy he bought it off of mixed 8 oz of oil to 5 gals gas. Is that about right? I think I saw on here to mix it 100:1 or 128:1? It seems like what he's telling me should end up somewhere around 75:1. I'm just estimating though. Does this seem right? It doesn't smoke with what he's got in it and not too bad of an odor. Also he was running husqavuarna oil since its for air cooled engines. I plan on running some Klotz synthetic I have on the garage.

[TheGDFP]

1oz/gal seems to be enough for these.
Adding oil to the gas makes it thicker, by a small amount, so some feel a size up on the main is a good idea. Also, oxygenated fuels are leaner in a carbureted engine, another cause for bumping a jet size or two.

[Jnkyrdg04]

So you say drop it down some? I know the motor was completely redone by the old man that owned it first and runs good. I just felt like that's was a strange mix. Maybe I should drop it down to 6-7 oz per 5 gals?

[TheGDFP]

I'm more accustomed to richer ratios, based on high-rev engines, but oil migration is slow in these, if run governed.

Oil in the gas is useless, until it drops from suspension inside the engine, and accumulates enough to be splashed at the bearings. At low speeds, more falls out and is available for lubrication, so less replenishment is needed. So, if governed, 1oz/gal. If you unhook the governor and wring the whiz outta it, use more. Oil is cheaper than top ends, and unless it's smoking obnoxiously, isn't hurting any thing.

Also, mix up what you plan to use in a week to two. Modern fuel is crap, goes bad when mixed, pretty quickly. Even the alcohol-free stuff uses heinous additives and goes gunky in a few weeks. The old 300-6 Ford has eaten my stale premix for a long time :)

[ldj1002]

I can't understand ONLY 1oz to gallon. I have had many 2 cycle engines in past 60 years. At first it was 8:1,, then 16:1, and finally 40 and 50:1 and I thought this will never work but it did. Then 2 years ago I got a golf cart and WHAT! 128:1. Again I thought this will never work but manual said it would and this forum also said it. I reluctantly did the 128:1 and for 2 years all is OK. Now, why such a small amount of oil when other 2 cycle engines need at least twice as much. This ez-go doesn't turn nearly as many rpm as the other 2 cycle engines or at least they don't sound like they do. Is that the reason?

[TheGDFP]

Originally Posted by ldj1002

I can't understand ONLY 1oz to gallon. I have had many 2 cycle engines in past 60 years. At first it was 8:1,, then 16:1, and finally 40 and 50:1 and I thought this will never work but it did. Then 2 years ago I got a golf cart and WHAT! 128:1. Again I thought this will never work but manual said it would and this forum also said it. I reluctantly did the 128:1 and for 2 years all is OK. Now, why such a small amount of oil when other 2 cycle engines need at least twice as much. This ez-go doesn't turn nearly as many rpm as the other 2 cycle engines or at least they don't sound like they do. Is that the reason?

Most of the reason is low revs. Harry Klemm did a lot of research, and numerous articles and tests have been done, suggesting similarly. Observed Trials bikes are running pretty lean, 60-100:1, again due to low revs not slinging the oil up the transfers and out the pipe.

125cc revvers are making more power at 18-24:1 even if they'd load up at low revs if they spent any time there.

Essentially, all of the engines with roller bearings, need about the same amount of oil to protect the bearings. High revs keeps more in suspension so less is left in the cases. Plodding along slower, more oil drops out and stays down where it can do it's job. There should be 1/4-1/2 inch of oil in the bottom of the cases on tear down.

Early stuff used low-grade oil, and many of the 8-16:1 engines had bronze connecting rods riding on steel cranks, no bearings.

Desire to reduce smoke output is a big part of the leaner ratios on some outboards/PWC, even though they rev a bit higher. Nearly infinite cooling system helps drop the oil out of suspension when mix hits cold aluminum, but lubrication failures are more frequent than ever.

I personally do not agree that 128:1 provides an adequate amount of protection. Reducing smoke can be done with modern oils, rather than starvation. These engines run much higher piston to wall clearances than conventional practice, mostly to crutch the lack of lube. Running 64:1 with synthetic, used within 2 weeks, and tightening up the clearance by .001-.0015 would let them make more power and live longer.

My opinions are merely that.

[dcotton4]

1 oz per gallon of gas 128:1

[Bikertrash00]

Terry, sounds like you would like me to fatten up my mix ratio a little?

[TheGDFP]

Originally Posted by Bikertrash00

Terry, sounds like you would like me to fatten up my mix ratio a little?

I personally feel that with the more aggressive engine, more oil would be good. Even an ounce and a half, 85:1 or so would help a lot.

[Bikertrash00]

Ok, I will fatten it up a bit!