Re: Pre-Mix Tricks?
The only problem you may run into with a big tank is not having enough room left for the oil after you fill it. When it sounds like its close to full add the correct amount of oil, then slowly fill it and see how much it will hold and then add the rest of the oil it needs. If you're a few oz's off don't worry about it, a few oz's in that much fuel won't make a difference.
After the first couple times you fill it, you should be able to tell when it's close to full, so just stop and add the oil at that point.
Adding it before or after you pump the fuel won't make a big difference, If it's on the trailer the gas will be mixed by the time you're out of the gas station, if you're on the water the boat is moving or rocking all the time. The only problem in adding it before you pump is if you over estimate the amount of fuel it will take and you add too much oil, there's no way to take oil out. It's not a huge problem unless you added far too much oil though.