How to determine proper oil mix?

[reelfishin]

Over the past year, I've scrapped probably around 40 or so boats, this has left me with a pretty good supply or premixed gasoline. The problem is, the when pumping out a tank on a boat destined for the big boat yard in the sky, I have no idea on how old the fuel is, or how much oil has been mixed in it. I've run a good bit of it though the yard equipment and even some in my old truck with no problems in the past but I've never trusted the oil content or condition to use it in any of my boats. Unless I knew the owner and was able to test run a motor with the fuel on board to some extent, I don't think I'd chance it in one of my own motors.
The point is now that I've got probably 7 or 800 gallons accumulated. Most in barrels stored in an outbuilding and some still in portable 5 gallon tanks as it was removed from the boats.
What really got my attention was one which I cut up last week, it had twin 100 gallon tanks, both full, two 25 gallon above deck tanks, also full, and 4 6 gallon portable tanks onboard, all full. The motor was running on the portable tanks.
I pumped each tank separate and checked for water, and all was clean, the motor was a premix motor, early 70s V4 and all tanks were still plumbed to the motor with various fuel lines and primer bulbs. The fuel has a gray blue look, so its got oil in it, but like so many others, I have no idea how much or how old, only that it appears free from water and didn't separate at all in a glass jar overnight. It smells fine, don't smell like old gas, and a sample runs fine in my lawn tractor with only some minor smoke. I've not yet run across any with really bad or stale smelling gas, at least not in any boats using premix. I am also curious if they add anything to two stroke oil to help stabilize the gasoline. I had one boat that I know sat for over 6 years, and I burned that gas in my old truck with no problems.
(I've since upgraded my shop truck to one more economical but I don't think dumping all sorts of old fuel into a modern fuel injected engine would be good idea, the old, carbureted, no catalytic converter, rust bucket didn't mind though).
Is there a way to determine the oil content or a way to maybe filter it out altogether as not to waist this much free gas?

 

[twostroke87]

Re: How to determine proper oil mix?

I would say take whatever you are going to use from your supply, and then add like you are doing a 100:1 mix with clean gas, that should keep you safe.

Watch out for those fiberglass tanks...they bite

 

[reelfishin]

Re: How to determine proper oil mix?

I haven't run across any fiberglass tanks yet, at least none that were still being used. The worst two I had to pump out were on I/O boats with straight gas that had turned dark brown. They had been sitting a few years or more.
It's hard to tell how much oil since there are so many different color oils and every oil looks different. What gets me is that many of the bigger tanks might actually have too much oil. I've seen it all too often where an owner will dump in some oil, then fill up at the gas station only to find out it won't take as much gas as he figured or he just plain added extra to be safe. If this goes on for the life of the boat, then the resulting mix is pretty heavy in oil after a while.

It's hard to tell a too much oil mix from a mix that just is darker in color due to the nature of a particular oil brand.

I did have one batch of gas, luckily a smaller tank, in which the owner in fact told me that he used to burn used oil in it, too cheap to buy new oil, he'd use drain oil which he strained through newspaper, they he'd use the newspaper to start his fireplace. That tank looked like a tar pit on the bottom. About 1/2" of sludge. I realize that for years it was normal to run #30 motor oil in a two stroke but I can't say some don't still do it.
It took me years to break one buddy of over mixing his fuel with oil, he'd dump in a full bottle in every tank, it started hard, smoked and finally carboned up so bad it wouldn't run any more. Had to be mixing about 25 to 1.
Another buddy still mixes his gas, even though his motor is injected and working. He don't trust the VRO system so he doubles up to be sure.
I've pumped a few out that were so dark in color it looked like a 50/50 mix of oil and gas.
Of course if these were well cared for boats, they wouldn't have been freebies and they wouldn't be getting stripped for parts and cut up.
I pick up a lot of them either for the trailer, the motor or other parts I can use or sell, the rest gets crushed and taken to the dump. A backhoe and dozer make short work of a glass boat.

 

[Chris1956]

Re: How to determine proper oil mix?

You might be able to use a hygrometer to determine the amount of oil in a mix. Other that that you are taking a big chance on the ratios. It is likely that all obvious gas-oil mixes are at least 50::1 since that is standard for all motors newer than 1964, but you can not anticipate all the wierd stuff the owners may have mixed in or omitted. They could have used automobile oil, ATF or antifreeze, by mistake.

In addition, the quality of the gasoline (age) may cause some combustion problems. With a cache of 700+ gallons, mixing a few gallons with new gasoline is impractical. Can you sell it for parts cleaning or some other worthy purpose?

 

[cc67]

Re: How to determine proper oil mix?

Old gas makes good charcoal lighter. Doesn't have near the umph as the fresh stuff.