change oil filter after only 300 miles but 18 months?

Question

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.

Answer 1

It kind of depends if the 300 miles was 3 hundred-mile trips, or 150 two-mile trips.

Moisture will condense into the oil, and if the trip is short enough, there won't be enough time at operating temperature to boil off the water.

This is BAD for the engine, as parts will rust and things will clog. Water will displace the oil on bearing surfaces, and water provides nearly zero lubricity.

OIL does not SPOIL! Lots of folk disagree with me, but there's a difference between oil being dirty and/or contaminated with water, versus oil that has had all the long-chain molecules sheared and no longer provides proper lubricity. Oil sitting in a jug, or sitting in a sump doesn't degrade from non-use. I'm sure the oil companies will tell you differently, but one has to judge their motivation.

If the classic Ferrari in your heated garage only gets 20 mile blasts on 20 Sundays for the year, the resulting 400 miles and "year" age is not justification to change the oil (in my never humble opinion). On the other hand, if you can afford a classic Ferrari, you would probably just tell your live-in mechanic to change the oil every six months...

To answer your question, I see no problem in not replacing the oil filter at this time. The filter should not break down in any way from simply sitting. I would take the vehicle on a few longer trips every so often to boil out any condensed water. I would also at least start and idle the vehicle every few weeks to keep the cylinder walls and bearing surfaces "wetted" with a fresh oil film.

On Edit:

Oil does not degrade significantly just sitting in a cold engine. On the other hand, if a car is driven just for very short distances, the oil will not fully heat up, and it will accumulate contaminants such as water, due to lack of sufficient heat to boil off the water. Oil in this condition, just sitting in an engine, can cause problems.

Source: Wikipedia - Motor Oil