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How long is synthetic oil good for?

Regardless of mileage, how long is fully synthetic oil good for? 6 months? 9 months? A year? I barely put 500 miles on this car during the summer and dont know what to do.

I wouldn’t go longer than a year.

Oil is MUCH more sensitive to mileage than it is to time…It doesn’t spoil sitting there in the crankcase…at 500 miles a year, I would not worry about going 3 years…

I would worry more about selling a car you don’t need…

If the car is used for a bunch of short trips and doesn’t get fully warmed up, that would decrease useful oil life, but if it’s used for a few longer trips, the oil would be good for a long time.

Another consideration I’d add is the age and potential future of the car. If you use a long (multi-year) change interval, that may reduce the chance that the car will get to 400,000 miles (or some other high number). With the car’s current lifestyle, it’s unlikely to accumulate a lot of miles. You might consider a shorter (one year) interval if you foresee using the car differently such that you might want hundreds of thousands of miles from it in the future. If you foresee only low-mileage use, long life (in terms of miles) is not a concern and a long interval may be suitable.

After living with two cars with GM’s oil life computer, I estimate that your car will be fine but GM says to change the synthetic oil once per year regardless of what the remaining oil life readout may be. If your remaining oil life went down 1% every 5 cold starts and you drove 5 miles per trip, the readout would go down only 20%. It’s possible that some of your starts are warm starts and some trips might be longer than 5 miles which would extend your oil life.

Like many questions, it can be answered by looking in your owner’s manual. If it does not give different recommendations for synthetic, then you use the same recommendations as non-synthetic. If you read the manual, it will say something like (10,000 miles or one year which ever comes first)

I’d say a year is OK. If you drive 2 miles daily, then the oil should be changed yearly. If you drive 60 miles once a week you might go for a few months more than a year.

The answer to the question depends a lot on how drive the car? Were those 500 miles mostly on a highway and on trips of more than 30 min.? Or, were they to town for food, like 2 miles and 5 or 10 min. trips?

Thanks everyone for your replies. The reason for the low mileage is that this is a 1969 Impala that I’ve restored (Rebuilt engine, trans and so on). When I do drive it though, I make a real effort to drive at least a good 10 to 15 miles. I’ve also gotten into the habit of not starting it at all during the winter, when just sits in the garage, because I’ve heard this does more damage than good to the engine.

I would change the oil every fall before you put it away, regardless of the mileage. That way it doesn’t sit all winter with contaminated oil in the engine. And I wouldn’t bother with the extra cost of synthetic in your situation.

I think that the 1969 owner’s manual will be a bit out of date considering the improvements made in oils in the last 40 years.

Change it once a year with normal oil. Fall, before putting it away for the winter would be the best time. You don’t even need to change the filter.

After a drive to get the stabilizer from the fuel tank to the motor (you do add stabilizer, correct?) drain the oil while it is warm and refill with regular 10W-30 oil. You’ll be ready to roll in the spring. Easy.

Starting it in winter is an interesting discussion. Starting any engine repeatedly and not allowing it to warm up fully results in condensation inside the engine and exhaust system. Since this engine is carburated, starting it and allowing it to idle could also be a problem unless it’s taken for a ride because of carbon buildup. Carbed engines run richer than modern EFI engines, and if the engine is repeatedly allowed to idle carbon can build up in the cylinders.

My suggestion would be to take it for drives when the weather is nice. That’s the best way to preserve it.