Engine Oil Change Interval for a car that is not used much ?

white91

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Mar 1, 2004
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Hello, I have a 1991 GT, that I have had since new.

It currently has 39000km (24500mi) on it.

I have always changed the oil every 5000km, or every year, which ever occurs first.

I have now also added a 2008 GT convertible to my collection.

Both cars will get driven during the summer, on weekends, when it is sunny.

My 91 GT is lucky to go through 3 tanks of gas a year, and I would expect the 2008 GT to be used about the same.

Both cars would get less than 20 hours of use per year.

My question concerns how often the oil needs to be changed? Does the filter need to be changed too?

Most manufacturers seem to time the oil changes after about 100 hours of usage.

It just seems that it is wasteful to change the oil with so few hours of usage.

Has anyone who uses their cars as much as I do, ever had the oil analyzed to see if it actually needs to be replaced?

Also, I have heard the old adage that says "oil is cheap, motor repairs are expensive", but I am looking for a scientifically based opinion.

As an example, my 2016 John Deere tractor has oil change intervals based strictly on hours of operation, there is no seasonal requirement to change the oil according to the dealer.

I would imagine that someone who has multiple vehicles in their collection, that see limited usage, would be able to provide their thoughts on this.

Thanks for your input,
Matt.
 
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This is what I do (hence, my opinion)...I changed my Mustang GT (2000 with 92k miles) a couple of weeks ago at just over the 14 month mark and less than 3500 miles. One year or 5000 miles is my target. I use Mobil 1 Extended Performance High Mileage Formula (15k miles). If I were racing it, I'd change it much more frequently to keep an eye out for metal in the oil.

I change my F250 6.0 Powerstroke at every 5000 miles (target), but it is often less than 5k because the diesel collects soot in the oil (worse with in town driving) and it causes the engine to run idle rough and act up when the soot clogs the injector oil passages.

I change Mrs' car every 5000 miles without regard to a timeline...and she usually drives between 12-15k a year.

Always change the filters...note--some industrial/marine applications change filters on a regular schedule while only changing oil when it fails testing.

Hope this helps.
 
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If in doubt, why not use the oil monitor ? First hit (change oil) change the oil . One can notice the frequency or miles driven will change with how the car is driven.

City, highway or track for instance.
 
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Long story short, old oil tends to contain byproducts if conbustion, fuel, moisture and other residues that can form an acid and attack parts of your motor.

I recommend an oil change at least yearly before storage if the car. For instance, if you are parking the car in Oct until April, I would take it out for your last cruise, change the oil, then let it sit with fresh clean oil over the winter.


I drive my car 200 miles a year, I change the oil before storage.
 
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My 93GT sees a few hundred miles a year, my routine is to change oil and filter at the end of the season before storage
and again in the spring.
Probably overkill but something about the oil sitting in the pan over the winter in my garage which can get pretty cold makes
me think I should dump it in the spring.
15w50 Mobil 1.
 
I've done something similar, change the oil before winter storage with some cheap generic oil, run it just long enough to circulate the new oil and get the residual old oil into the pan, then change it again in the spring with the good oil. The cheap oil over the winter basically just preserves the engine, you're not driving on it. Don't do this anymore since car has 95000 on it, but I would do this for a new or rebuilt engine.
 
Changing oil that has not been run enough to get blow by in it is really not necessary.
The oil was in the ground for a long time. In it’s refined state, the oil will not deteriorate in that amount of time. The additives will not have a chance to be used up in a cold, parked motor either.
The idea of reusing an oil filter is FAR more concerning to me. The filter media, cardboard and adhesives in low end filters is much more likely to break down over time than slightly used oil is. After the recent wave of You Tube filter comparisons, I saw some brands have changed since I last worked a parts counter where we set up displays with opened filters. Wix/Napa Gold is now the only brand I trust on an engine for more than a year. My back stock of orange ones were rusting inside and went to the landfill unused.

My 93GT sees a few hundred miles a year, my routine is to change oil and filter at the end of the season before storage
and again in the spring.
Probably overkill but something about the oil sitting in the pan over the winter in my garage which can get pretty cold makes
me think I should dump it in the spring.
15w50 Mobil 1.
 
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Changing oil that has not been run enough to get blow by in it is really not necessary.
The oil was in the ground for a long time. In it’s refined state, the oil will not deteriorate in that amount of time. The additives will not have a chance to be used up in a cold, parked motor either.
The idea of reusing an oil filter is FAR more concerning to me. The filter media, cardboard and adhesives in low end filters is much more likely to break down over time than slightly used oil is. After the recent wave of You Tube filter comparisons, I saw some brands have changed since I last worked a parts counter where we set up displays with opened filters. Wix/Napa Gold is now the only brand I trust on an engine for more than a year. My back stock of orange ones were rusting inside and went to the landfill unused.
An old mechanic friend laughs at me because I use wix filters, they started out as an industrial filter manufacturer, been around a long time.
 
Every 5k miles or one year for me, for reasons stated by mustang 5l5. 7991lx is also correct. Oil and filter both regardless.

To me, changing in the fall and then in the spring seems like a big waste. I hope you capture that virtually unused oil and use it for chain saw bar/chain lube or something. Wix filters are good. I use fram ultra which it's an excellant filter and so are royal purple filters.