Mixing oils in lawn tractor like a dummy

It’s conceivable that I accidentally mixed sae 30 and 10w30 oil (1 qt each) in my 20 hp Koehler/craftsman lawn tractor today when I changed the oil. We can’t be sure since there were no witnesses. Should I wait until Monday when the wife goes to work and stealthily drain it and replace with 10w30 as God intended, or just let it ride?

It won’t hurt a thing. Leave it alone and worry about other things.


The manual for my 32 year old mower specifies 30 weight. In the last several years I have used full synthetic 10W-30. With air cooled engines used just in the summer as in a mower application, the mixture of 10W-30 and.straight 30 is fine.
I have a generator that does have specific requirements for 5W-30 synthetic and I adhere to these specifications because I never know if I will need the generator in the dead of winter or after a power outage caused by wind or lightning in warmer months. However, I don’t have to mow in cold weather.

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Mind you, I can worry about many things simultaneously.


I think most specified straight 30 in the summer and 10-30 or 5-30 in the winter. Briggs now says 5-30 synthetic is OK year round so that’s all I use anymore. So yeah, no problem.

As long as you don’t have a snowblower attatchment for your mower you will br fine.

Sadly I do use it to haul stuff around in winter. I’ll change the oil to 10w30 at the beginning of November. Thanks guys!