For a seldom driven 2002 Buick Century (most trips are city for 6-9 miles, some on a highway for 10 minutes or so @ 55mph), mileage over the past 18 months was only 300 miles (no typo, that's three hundred). The oil on the dipstick looks new, i.e. honey colored and clear. Total on odometer is ~20k miles.
I bought the oil and filter to change both. However, it seems that it would be extremely difficult to change the filter because it's in a very tight spot as far as accessibility. I could probably get the filter off, but getting it threaded back on might be impossible. Maybe so anyway, then I'd be stuck and couldn't drive. I tried today laying on the ground as I've done with various cars over decades - but this car is the worst ever.
(Here's a vid of a guy removing a plastic shield underneath to get better access: https://youtu.be/IMqeuhsIP8c?t=3m57s starts after the shield is removed. Doing that same thing might just get me in deeper problems, I don't know.)
So then, how much risk is there is changing only the oil but not changing the filter after 300 miles and 18 months? Can a filter get gunked up over time even with very low miles? Can engine oil sort of coagulate in a filter? The current filter is whatever Sears had put in 18 months ago. I'd rather not have my new 5 qt jug of oil go to waste. I suppose that next summer I'd pay a shop to replace both.
The closest other question I see is this: Can I change the oil without changing the filter? but that has to do with 12k mile intervals and being "driven hard". Thanks.