Logo
FULL SITE MENU

10W40 Oil Used in Fuel mixture

S

seanfawcett

New member
Hi:

I just purchased a sailboat that came with a small inflatable dinghy and a 4 HP Johnson Seahorse outboard. (don't know the year). The motor seems rot run fine (smoked just a little) but after running a few minutes I looked at the oil bottle that was in the boat... It was 4 cycle 10W40 engine oil!!!

I asked the previous owner and he confirmed that he accidentally used that in the most recent gas mixture. I am not sure how long the motor ran with this mixture but it may only have been 30 minutes or so in short (5-10 min) trips from the dinghy dock to the sailboat.

I drained the gas, and filled the tank with 93 Octane gas and a 40:1 mixture of Starbright 2-cycle oil. I also added just a little SeaFoam for good measure.

The question is: What sort of damage could have been done by running on a 10W40 mixture?

The motor seems to run fine now but what should I be aware of?

Thanks
 
There shouldn't be any issues with that if it was run only for a short time. I wouldn't do it anyting long distances however. The problem with running that kind of oil in a two stroke motor is that there is a lot of additives that will build up in your motor and that will cause damage over time. You made the right choice of dumping it out and putting fresh oil and gas there. The seafoam will help clean out anything that may have built up over the years.

If you had the choice and there was no alternative running straight gas or gas mix with 10 w40 to get you out of an emergency definitely mix the 10 w40 at about 20 to 1 mixture and at least it will keep the bearings from burning out..

There is a big difference between 10w 40 motor oil and the older 40 weight non detergent motor oil which happened to be used in outboard motors for years. In my outboard motors I use Evinrude xd 30 mixed at 50 to 1. In my other 2-stroke Motors mostly chainsaws, I mix my oil 20 to 1 mixture with 91 octane fuel. The oil that I happened to use is 30 weight non detergent motor oil. I have been doing it that way for 10 plus years and I have zero problems with the saw. But that's just what I do, to each their own.
 
Last edited:
BRUPP79 said:
There shouldn't be any issues with that if it was run only for a short time. I wouldn't do it anyting long distances however. The problem with running that kind of oil in a two stroke motor is that there is a lot of additives that will build up in your motor and that will cause damage over time. You made the right choice of dumping it out and putting fresh oil and gas there. The seafoam will help clean out anything that may have built up over the years.

If you had the choice and there was no alternative running straight gas or gas mix with 10 w40 to get you out of an emergency definitely mix the 10 w40 at about 20 to 1 mixture and at least it will keep the bearings from burning out..

There is a big difference between 10w 40 motor oil and the older 40 weight non detergent motor oil which happened to be used in outboard motors for years. In my outboard motors I use Evinrude xd 30 mixed at 50 to 1. In my other 2-stroke Motors mostly chainsaws, I mix my oil 20 to 1 mixture with 91 octane fuel. The oil that I happened to use is 30 weight non detergent motor oil. I have been doing it that way for 10 plus years and I have zero problems with the saw. But that's just what I do, to each their own.
Click to expand...

Thanks so much! Very informative reply!
 
Back
Top