Thanks everyone for the feedback. The 5 qt. thing is due to Walmart. Some other places have larger, and I will keep an eye out for them.
I have a summer and winter fill in name only. Calling it the Sep-Mar fill and MarSep fill is just not as easy. I know that PP is great in the car and the remainder of the quart will last me years. In the worst case, If the G loves the M1, I could always have the best lubricated lawnmower in the neighborhood.
Caterham, nice catch. The good thing about getting into deep coprolite is that the cleanup is so much easier.
This whole thing wouldn't be an issue if I had another vehicle to use up the leftovers. Although the lawnmower remark was a bit on the sarcastic side, it wouldn't mind having mongrel synthetic. Right now the G is only dating. When she settles down, cracking that extra quart will be done without an extra thought.