How often should one change low mileage vehicles due to acids?

[AtomicNumber53]

The old claim with conventional oil was replace every 3,000 miles or 6 months, whichever comes first. Someone on Facebook told me that synthetics don't have the same acid problem that conventionals have, so mileage is the only thing determining when one should change their oil. Definitely interested in this as a few vehicles I have don't even see 3,000 miles in a year, but I have been changing them yearly with Synthetic SuperTech pretty much because I'm afraid of acid buildup. I'd love to replace my synthetic oil every 3 years if it really doesn't cause any harm. Is this claim that synthetics don't form acids based on typically higher TBN values, or is there more to it?

 

[Quattro Pete]

Originally Posted by AtomicNumber53

Someone on Facebook told me that synthetics don't have the same acid problem that conventionals have,

Not true. If you are short tripping, then you'll have excessive moisture and fuel build up regardless of what oil you use. As far as how often to change it, it depends on how the vehicle is driven. If short tripping, you'll need to change it more often. If you take it for longer drives, then you may get away with longer intervals. I change oil annually on my low mileage car.

 

[Ihatetochangeoil]

This thread is from August of 2016, I don't think the UOA link works anymore, but the UOA was so normal it was boring. 5 years and less than 2K miles...https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4190879/1992-surburban-big-block-m1-10w-30-5-year-oci Here is a Jaguar with 9 year old oil...https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4533985/mobil1-0w-40-supersyn-10200km-9-years-oci You may find this long but I find interesting read: https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4354597/1

 

[WagonWheel]

My understanding is it won't turn acidic until the additives that form the TBN are depleted. This is regardless of which oil you choose. If you are curious you can grab a sample with a $12 Rock Auto UOA kit and see the actual results and let you know how long you can go.

 

[eljefino]

Originally Posted by WagonWheel

My understanding is it won't turn acidic until the additives that form the TBN are depleted. This is regardless of which oil you choose. If you are curious you can grab a sample with a $12 Rock Auto UOA kit and see the actual results and let you know how long you can go.

Yes and this is somewhat- to well-past the normal changeout interval. Old oil still protects. Decrepit oil doesn't. If you don't start the car that day, it doesn't count as a day. So you can go years.

 

[Ihatetochangeoil]

Originally Posted by WagonWheel

My understanding is it won't turn acidic until the additives that form the TBN are depleted. This is regardless of which oil you choose. If you are curious you can grab a sample with a $12 Rock Auto UOA kit and see the actual results and let you know how long you can go.

This is absolutely correct. The IDEAL time to change your oil is as the additives deplete, the TBN number goes down, and the acid number (TAN) goes up. When they cross, it's time for an oil change. Unfortunately, you will NOT find this "sweet spot" with one UOA...I guess the practical alternative is to err on the conservative side. My advice to you is to postpone your oil change until you can't sleep at night, whether that is one year and one day or two years; whatever. When it bothers you, take a sample and send it in to Blackstone, Horizon, Rock Auto, or whoever. Until you actually have a UOA or two or three, anything that anyone says is speculation. Your UOA need not be all the time; you're just setting precedent and learning when is a good oil change interval for YOUR car and YOUR driving habits/conditions...Of course, you may find my advice worth what you've paid for it. Peace be unto you.

 

[alcyon]

Isn't there a danger of the additives falling out of suspension ?

 

[dave1251]

Originally Posted by Ihatetochangeoil

Originally Posted by WagonWheel

My understanding is it won't turn acidic until the additives that form the TBN are depleted. This is regardless of which oil you choose. If you are curious you can grab a sample with a $12 Rock Auto UOA kit and see the actual results and let you know how long you can go.

This is absolutely correct. The IDEAL time to change your oil is as the additives deplete, the TBN number goes down, and the acid number (TAN) goes up. When they cross, it's time for an oil change. Unfortunately, you will NOT find this "sweet spot" with one UOA...I guess the practical alternative is to err on the conservative side. My advice to you is to postpone your oil change until you can't sleep at night, whether that is one year and one day or two years; whatever. When it bothers you, take a sample and send it in to Blackstone, Horizon, Rock Auto, or whoever. Until you actually have a UOA or two or three, anything that anyone says is speculation. Your UOA need not be all the time; you're just setting precedent and learning when is a good oil change interval for YOUR car and YOUR driving habits/conditions...Of course, you may find my advice worth what you've paid for it. Peace be unto you.

That wives tail of crossover was debunked many moons ago. Oil will needed to be changed when TBN is depleted, or shears way out of grade, oxidizes to the point of leaving deposits, and or any combination above. Testing shows motor oil left in the sump of a short tripper can be good for years.

 

[Linctex]

Originally Posted by Ihatetochangeoil

This thread is from August of 2016, I don't think the UOA link works anymore, but the UOA was so normal it was boring. 5 years and less than 2K miles...https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4190879/1992-surburban-big-block-m1-10w-30-5-year-oci

This link works fine! https://www.bobistheoilguy.com/foru...surburban-big-block-m1-10w-30-5-year-oci I was trying to find this the other day - - thanks for finding it!

 

[SonofJoe]

In 2019 'Murica, you should not be afraid of acid build-up in crankcase oil. The old 3,000 mile/3 months oil change rule dates back to the days of simple, non-hydrotreated Group I (solvent extracted, MEK dewaxed) mineral base oils which contained appreciable amounts of aromatic hydrocarbons (& more specifically, lots of 'attackable' benzylic hydrogen sites). These base oils, when exposed to hot blow-by gas would readily oxidise to form carboxylic acids. However with these oils, you were always less bothered about acid attack in its own right & way more concerned about runaway oil viscosity (I've seen oils hit a KV100 of 5,000 cst in extreme cases!). As you move away from Group I's towards hydrogenated Group II's & III's, the base oils become more & more resistant to oxidation & produce less acid. Put simply, 8 TBN's worth of overbased metallic detergent will last far longer in a Group II or III oil than it will in a basic Group I oil. However all oils, even PAO & Esters will oxidise & acidify if you leave them in the sump for long enough, which is why the fill-for-life engine oil will never exist. PS - I've run many a 'passing' engine test when the entire TBN reserve has been depleted after say 30 hours & TAN has run rampant. Import as it is, TBN is just one factor in the fight to control oil oxidation. When TBN disappears, other components come into play.

 

[DR1]

I drive approx. 10k miles yearly local no major long trips with full synthetic 5w30. How many time per yr should I change oil and filter?

 

[SonofJoe]

Originally Posted by lawnguy

I drive approx. 10k miles yearly local no major long trips with full synthetic 5w30. How many time per yr should I change oil and filter?

I'd say once every 10k for both oil & filter. My Suzuki's 0W20's recommended OCI is every 12.5k miles or every year (whichever comes soonest). Now I'm retired, I don't do that many miles so I'll very likely change the oil/filter every 10k miles but every other year. Despite what you might hear, there's absolutely nothing wrong with keeping a modern synthetic in the sump for a couple of years.

 

[AtomicNumber53]

Originally Posted by dave1251

Originally Posted by Ihatetochangeoil

Originally Posted by WagonWheel

My understanding is it won't turn acidic until the additives that form the TBN are depleted. This is regardless of which oil you choose. If you are curious you can grab a sample with a $12 Rock Auto UOA kit and see the actual results and let you know how long you can go.

This is absolutely correct. The IDEAL time to change your oil is as the additives deplete, the TBN number goes down, and the acid number (TAN) goes up. When they cross, it's time for an oil change. Unfortunately, you will NOT find this "sweet spot" with one UOA...I guess the practical alternative is to err on the conservative side. My advice to you is to postpone your oil change until you can't sleep at night, whether that is one year and one day or two years; whatever. When it bothers you, take a sample and send it in to Blackstone, Horizon, Rock Auto, or whoever. Until you actually have a UOA or two or three, anything that anyone says is speculation. Your UOA need not be all the time; you're just setting precedent and learning when is a good oil change interval for YOUR car and YOUR driving habits/conditions...Of course, you may find my advice worth what you've paid for it. Peace be unto you.

That wives tail of crossover was debunked many moons ago. Oil will needed to be changed when TBN is depleted, or shears way out of grade, oxidizes to the point of leaving deposits, and or any combination above. Testing shows motor oil left in the sump of a short tripper can be good for years.

Could you elaborate on this? When TBN is less than 1, then the oil should be changed? Or what is it I'd really be looking for on a UOA?

 

[Jstew]

I have a hard time changing perfectly good oil, and have had an interest in this topic for the last few years - I'm currently (and carefully) monitoring my 2 year OCI's on my 1969 Corvette. I use Brad Penn 10w30, and drive it 500-1000 miles a year. No short trips, Qjet carb (so fuel is metered perfectly ...€). TBN after my last Blackstone report @ 2yr / 1000 mi (back to back 500 mile/year), was a robust 7.6 with fuel dilution <0.5. Blackstone says I could go longer, so I'm contemplating a 3 yr interval with a sampling. Like many here on the forum, I believe changing oil too often is expensive (especially for the BP!) and wasteful.

 

[bullwinkle]

Originally Posted by lawnguy

I drive approx. 10k miles yearly local no major long trips with full synthetic 5w30. How many time per yr should I change oil and filter?

I do my xB roughly once a year under the same conditions you describe-but it warms up fast due to a tiny 200 pound all aluminum engine, gets taken on reasonably long runs regularly, and the M1 EP 5W30 was tested & shown to be capable of staying in grade for 10K. M1 0W30 AFE, with it's alleged PAO/Grp. IV base, was SHOT in 7K, sheared into a low 20 grade. UOA is always your friend when extending, even if you only do a couple.

 

[WobblyElvis]

I had one UOA from blackstone with a TBN of 1.0 and they still recommend I take the oil out another 1,000 miles.

 

[mclasser]

My old Accord sees about 6500 miles per year, mainly local driving with a highway trip once and a while to get things warmed up. I do once a year syn oil changes. I have to add 1 qt of makeup oil during this time, so I figure this replenishes the add pack a little.

 

[AtomicNumber53]

Originally Posted by AtomicNumber53

Originally Posted by dave1251

That wives tail of crossover was debunked many moons ago. Oil will needed to be changed when TBN is depleted, or shears way out of grade, oxidizes to the point of leaving deposits, and or any combination above. Testing shows motor oil left in the sump of a short tripper can be good for years.

Could you elaborate on this? When TBN is less than 1, then the oil should be changed? Or what is it I'd really be looking for on a UOA?

Am very curious about this.... As long as TBN is over 1, acids won't cause harm? Also.... I remember people were talking about garaged vehicles at the beginning of this thread. I'm assuming the garaged vehicle would be able to go longer because of less condensation?? Is that correct?

 

[bbhero]

Originally Posted by SonofJoe

Originally Posted by lawnguy

I drive approx. 10k miles yearly local no major long trips with full synthetic 5w30. How many time per yr should I change oil and filter?

I'd say once every 10k for both oil & filter. My Suzuki's 0W20's recommended OCI is every 12.5k miles or every year (whichever comes soonest). Now I'm retired, I don't do that many miles so I'll very likely change the oil/filter every 10k miles but every other year. Despite what you might hear, there's absolutely nothing wrong with keeping a modern synthetic in the sump for a couple of years.

Great post soj... Plus the longer post above was outstanding as well. It is really good to have you on here.

 

[demarpaint]

Originally Posted by AtomicNumber53

Originally Posted by AtomicNumber53

Originally Posted by dave1251

That wives tail of crossover was debunked many moons ago. Oil will needed to be changed when TBN is depleted, or shears way out of grade, oxidizes to the point of leaving deposits, and or any combination above. Testing shows motor oil left in the sump of a short tripper can be good for years.

Could you elaborate on this? When TBN is less than 1, then the oil should be changed? Or what is it I'd really be looking for on a UOA?

Am very curious about this.... As long as TBN is over 1, acids won't cause harm? Also.... I remember people were talking about garaged vehicles at the beginning of this thread. I'm assuming the garaged vehicle would be able to go longer because of less condensation?? Is that correct?

If the garage isn't properly vented there could be more condensation. Does it matter if the engine is off? The same can be said for damp humid climates, in fact that might be worse than the garage depending on the location. How about a poorly vented garage in Florida? That could be very damp.