Can synthetic oil extend time-based drain interval?

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148
Location
CA
For a car with low annual mileage (e.g. 4000 miles/year) that's mainly used for short, around-town driving and the occassional weekend trip, I've been following a time-based drain interval (every 4-6 months) instead of a mileage-based drain interval. I hear a lot about how the main benefit of synthetic is being able to go 7.5K-10K miles between changes vs. 3.5-5K with a dino oil. Would this extended drain interval also apply to a time-based drain interval? In other words, if I switched to synthetic, can I change it out every 10-12 months instead of every 4-6 months? P.S. Manufacturer recommendations for this car are: Normal: 7.5K/6 months, whichever comes first. Severe: 5K/4 months, whichever comes first.
 

Patman

Staff member
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21,989
Location
Oakville, Ontario
I believe this to be true. With synthetic oil being able to fight off the effects of moisture better, it's a better candidate for being left in the engine for a full year than dino oil is.
 
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82
Location
Texas
I through use of and reading about have become a fan of the PAO blended oils . It seems they do very well for less money . There are only a few available though that has a fair amount of PAO but any amount seems better than none in most cases . I am not trying to convert others to use a blend just posting what I think works for me in some cars. It appears in a mineral oil some of those HD Diesel oils that are available in 10/30 wts would work fine for a car used like the topic car .
 
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3,693
Location
Chattanooga, TN
I have two cars on time going on three. One does about 8000 miles a year and I change the filter at 6 months. Another just once a year only (no filter change) about 3000 miles this year and another is taking about 9 months to get to my 7500 change interval on it. Analysis has been fine so my limits now are mileage or one year whichever comes first. Amsoil products are used.
 
Messages
1,412
Location
Falls Church VA
For your kind of driving, one year drain should be fine, particularly with AMSOIL or Mobil 1. I changed the oil in my mother's old Ford 3 times in 111-12 years, mostly because I knew the formulation had been updated. Of course, she didn't put near 4,000 miles a year on it (really only got run when my brother or I visited).
 
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951
Location
Loveland, Colorado
quote:
Originally posted by Dick in Falls Church: I changed the oil in my mother's old Ford 3 times in 11-12 years, mostly because I knew the formulation had been updated. Of course, she didn't put near 4,000 miles a year on it.
Dick, Are you saying that you were comfortable enough with Amsoil to only change the oil once every 4 yrs?
 
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5,785
Location
Dixie
Kreativ, Yes, I do this on a regular basis with my truck ...I've changed the oil 3 times in the last 5 years and have twice run 2 year oil change intervals. I also followed this same procedure with the '85 Jetta I owned - I would typically put 6000-8000 miles/year on that motor. However, I still change filters every 6 months and topoff the crankcase. The filter materials will degrade when exposed to the contaminents in used oil - particularly gasoline. The first 2 times you do this I would take an oil sample after six months and have it tested, in particular to see how much water and/or fuel dilution you are seeing.
 

Jay

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1,607
Location
Idaho Falls, ID
So you're interested in shelf life more than mileage? Mobil 1 claimed a shelf life of 120 months for unopened bottles of the old Trisynthetic.
 
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1,412
Location
Falls Church VA
>>>Dick, Are you saying that you were comfortable enough with Amsoil to only change the oil once every 4 yrs? Sure-- some years, when I remembered, I did change the filter and drop another quart of oil in there.
 

kreativ

Thread starter
Messages
148
Location
CA
What's the longest amount of time you'd feel comortable going in between oil changes if using dino oil? Assuming: - Mileage is low enough that it never becomes an issue vs. time. - The car does get driven on longer trips every now and then, which would hopefully evaropate any moisture that has collected. - Pennzoil 10W-30 dino is being used.
 
Messages
951
Location
Loveland, Colorado
Hey kreativ, I think I'm sensing a "test vehicle" in the making here! Maybe some of the Oil Analysis Anonymous members would be willing to help "sponsor" your test? [LOL!]
 

kreativ

Thread starter
Messages
148
Location
CA
[Big Grin] They'd probably want someone more serious and knowledgable about motor oil. Reason I ask about dino oil as well is because when I requested synthetic at the dealer, they told me not to use synth until after 10k miles. At the current rate this car is building up mileage, it could take a few years to get past 10K. Considering the dealer charges $80 for a synthetic oil change, it doesn't sound like they'd try to persuade me not to use synthetic unless they had a good reason to. Much thanks for all the feedback so far! I see some seriously long time-based drain intervals with synthetic in this thread. Would those of you willing to go multiple years between changes do the same if using Mobil1 10w-30? Not sure how that compares with Amsoil.
 
Messages
5,785
Location
Dixie
Kreativ, This is mostly a matter of TBN retention ...you are going to also get some water and fuel dilution under these conditions, the extent of which is impossible to predict. So if I was doing this with either Amsoil or Mobil 1, I'd check the physical appearance of the oil from time to time and I'd do an oil analysis after 6 months. If you have a TBN of at least 8.0 @ 6 months; water was <.1% and fuel was <1.0%, I'd feel fine going another six months without draining.
 
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3,023
Location
USA-Michigan
I keep the same oil in my 1964 Impala for 5 yrs. I only drove it about 1000 miles in those years. I would look at the oil in the fall and it looked ok, so I left it in. Was using Amsoil 10W-40 and an Amsoil filter. That was a few year back, just before I sold it this spring the 10W-30 oil had been in there about 2 yrs+. I had the car since 1985 when I restored it with a rebuilt 327-250 HP. When we fired it up for the first time, I ran it 30 minutes at around 2000+ rpm on petro oil to break in the cam, we shut it down and installed the 10W-40 synthetic and never looked back. It never used any oil, I put about 10-15,000 miles on it since 1985 but very few in the last couple of years.
 
Messages
3,346
Location
Clarksville, Tennessee
quote:
Originally posted by kreativ: I hear a lot about how the main benefit of synthetic is being able to go 7.5K-10K miles between changes vs. 3.5-5K with a dino oil. Would this extended drain interval also apply to a time-based drain interval? Normal: 7.5K/6 months, whichever comes first. Severe: 5K/4 months, whichever comes first.
Sure both Tooslick and myself rarely put high mileage in 1 year. Before I went to the by-pass I went over 18 month without changing the oil. I recommend to use a quality synthetic, change the oil once a year with a filter change at 6 months. Though another senerio would be to use a quality synthetic change filters at 6 months and do oil analysis once a year, change in about 3-5 years!!. With the filter change at 6 months you should be topping off any additives to keep your protection up. With low milage wear metals should be in check. After 18 months in my truck the oil was still doing great(though I can tell I didn't do the filter change only did it once at the first 6 months). I'll have to dig the analysis out and post it.
 
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2,077
Location
Cordelia, CA
Personally, I'd not go longer than 6 months. I ran Mobil 1 in my 93 Olds Ciera while I was putting 20k+ miles per year on it with a 10-11k interval. When I gave it to my grandmother, I switched it to Pennzoil with a 3-4k interval, because she only drives 7500-10k per year.
 
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