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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.

  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Oct 31 '18 at 21:09
  • Check the manual ; I would be amazed if it does not recommend changing oil at least once a year regardless of mileage. A friend ruined his engine under similar conditions , except his trips were only about 5 miles. – blacksmith37 Nov 1 '18 at 1:21
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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

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    I'm with you on this one @SteveRacer, 300 miles isn't enough to warrant a filter change. – GdD Nov 1 '18 at 9:06
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    Thanks, SteveRacer. Your analysis sounds very well reasoned. It helps, too, that @GdD seconded. Since I have the oil on hand and being wary of results like blacksmith37 described, I decided to put the oil in today - but that immediately led the the next thwarting: mechanics.stackexchange.com/questions/60469/… – Bob3411 Nov 1 '18 at 21:23
  • @Bob3411 I'm glad. I would never object to anyone wanting to change their oil. I have waxed infinitely on this topic, and made few friends. The problem with oil is that IT GETS DIRTY from use... and that's true for $2/quart dino juice Walmart stuff, or $1000/quart synthetic miracle demon juice milked from Siberian Ant glands. Dirty is bad, and the abrasive particles accumulate from IC combustion. You could used the best boutique Gin, or leftover bacon fry fat. IT DOES NOT MATTER. Oil gets "dirty" long before it loses lubricity. We should change our oil often, to get the dirt out! – SteveRacer Nov 2 '18 at 10:06
  • That said, I continue to yell from my old hippie bully stump . . . Oil DOES NOT SPOIL . . . – SteveRacer Nov 2 '18 at 10:07
  • @SteveRacer, how do you reply to the claims that it's the additives that degrade over time, regardless of miles? Has anybody tested that, just by letting oil sit for a year or two or three? (and thanks again) – Bob3411 Nov 3 '18 at 21:25

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