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Old 01-27-2005, 12:39 PM   #1
Kitt
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Default Oil change: every 3 months or 3,000mi?

Every 4 months I only put about 2,000 miles on my car (Mobil1 synthetic). Should I still follow the rule of doing an oil change every three months even though I'm using synthetic oil? or just change it every 3-4,000miles no matter how many months pass? Thanks
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Old 01-27-2005, 12:46 PM   #2
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We have stickys at the top of each forum for commonly asked questions. In fact, this topic is covered in DETAIL with one of those stickys. I'd recommend reading it since I put in about 20-30 hours of research into it and it answers your question in minutiae.
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Old 01-27-2005, 12:51 PM   #3
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Personally, I don't think that time has any ill-effects on oil, unless it just sits long enough in between drives and collects moisture. I would go by how many miles you think it should be changed by. You can go by how the oil looks on the dipstick to tell if it needs changed, or in other words, how dark it is on the dipstick. Many people think it is only because the oil breaks down, but it also cleans the inside of the engine. So I wouldn't go by an extended period of time. Just because it is synthetic oil, doesn't mean it will be good for 10,000 miles because that is 10,000 miles of dirt in the oil. When I use synthetic, which I use in my WRX, I don't go over 5,000 miles and try to change it between 4 and 5,000. I may be changing it quicker than other people, but it doesn't hurt the motor any to have clean oil, whereas it can hurt it to have dirty oil. Just my opinion.
BTW, the 3 month/3000 mile is just an average. National average is that a car owner will put 1000 miles on their car a month. Thats where they get 3 months. Like I said above, I think the mileage is more important than the time period. Just change it whenever you feel the oil is getting too dirty.
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Old 01-27-2005, 03:11 PM   #4
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According to the FAQ, Subaru wants you to use time as a factor. Its not just the possible accumulation of moisture that's an issue. This time of year (cold, winter temps) your car spends more time in "open loop". This means the ECU has the engine in warm up mode and is pretty much ignoring the O2 sensor to control fuel mixture. Its like a choke on a carb engine. A richer fuel mixture is not only ineffecient, but it also results in unburned fuel. That unburned fuel is washing down the cylinder walls and contaminating the oil. If you don't change the oil on a regular basis (three months), you get some pretty nasty stuff in the crankcase. This is part of the reason that your oil gets black when its dirty (the other is blowby).
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Old 01-27-2005, 03:43 PM   #5
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Quote:
Originally Posted by skyhawk
Personally, I don't think that time has any ill-effects on oil, unless it just sits long enough in between drives and collects moisture.
If you're not putting a lot of miles on the car during a given time period, it is a good bet that the car is going to be sitting long enough between drives to collect moisture and/or the drives are too short to boil any water out of the oil.
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Old 01-27-2005, 04:18 PM   #6
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Mobil 1 should be able to go at least 5000 miles under pretty much any circumstances. I would say 5000 or 6 months, whichever comes first. Just be sure to take it out on the freeway for a long spin every so often...
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Old 01-27-2005, 07:09 PM   #7
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Quote:
Originally Posted by poison
Mobil 1 should be able to go at least 5000 miles under pretty much any circumstances. I would say 5000 or 6 months, whichever comes first. Just be sure to take it out on the freeway for a long spin every so often...
2nd that
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Old 01-27-2005, 07:44 PM   #8
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OK, the last three posts (four, including mine) come from Californians. If they have not lived in colder climates, then they are excused from the effects of sub-zero temperatures on oil. I, however, was born and raised in a cold climate and prefer to change my oil with the seasons.
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Old 01-28-2005, 01:21 PM   #9
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in the U.K., the scheduled manufacture oil change time is 5K miles
this is b/c oil is soooo much more expensive there.
~
if they can wait until 5K, i see no reason why a USDM veh could also wait.
~
i have always changed mine at 3k FYI.
steven
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Old 01-29-2005, 11:39 AM   #10
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thanks guys, I asked because I haven't changed my oil since september but only put 2,000miles on the car.
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Old 01-29-2005, 10:05 PM   #11
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Did you see the prize winning letter to the editors in the latest Car & Driver? The mechanic who tells how folks change their 7 dollar a quart synthetic at 3 months or 3000 miles, and he drains it, and then puts it into his cars since it's got 70% of it's life left!
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Old 01-30-2005, 03:27 PM   #12
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Quote:
Originally Posted by Alan
Did you see the prize winning letter to the editors in the latest Car & Driver? The mechanic who tells how folks change their 7 dollar a quart synthetic at 3 months or 3000 miles, and he drains it, and then puts it into his cars since it's got 70% of it's life left!
I would do that too if I had a 90 Escort to put it in.

Unfortunately the 90 Escort used more oil than I could supply from frequent synthetic oil changes. On the plus side, the Escort didn't need oil changes, since all I had to do was pour cheap oil in all the time. Why baby a practically free beater car?

Once again circumstances rule, and there is no primordial golden rule for this topic.
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Old 01-30-2005, 05:22 PM   #13
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Quote:
Originally Posted by Alan
Did you see the prize winning letter to the editors in the latest Car & Driver? The mechanic who tells how folks change their 7 dollar a quart synthetic at 3 months or 3000 miles, and he drains it, and then puts it into his cars since it's got 70% of it's life left!
Little bit different when your oil is also being used to cool a turbocharger that can see temps of up to1200- 1500 degrees.I mean if the exhaust is that hot,so is the unit its coming out of.Most engines don't see over 220 degrees.
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Old 01-30-2005, 06:54 PM   #14
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Quote:
Originally Posted by dumdum
I mean if the exhaust is that hot,so is the unit its coming out of.Most engines don't see over 220 degrees.
Actually the exhaust coming out of most engines is about the same temperature as the exhaust from our turbocharged cars. And a turbo, or the engine for that matter does NOT have to be at the same temperature as the exhaust, that's why it has cooling to keep it from getting too hot. The uncooled parts do get very hot, but the parts the oil lubricates and cools are kept at temperatures the oil can handle.

BTW -I use synthetic and change it every 4000 miles or 5 months on my WRX.
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Old 01-31-2005, 01:19 PM   #15
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three times a year for me, regardless of miles. mobil 1. blackstone labs is your friend.
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Old 02-04-2005, 03:29 PM   #16
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I'm thinking of going to AMSOIL 5w30 with their filter; and doing a oil change every 6 months or 7500 miles (~twice a year for me). Anyone else had good results with this kind of oil and schedual? The AMSOIL 5w30 is suppose to be able to go 25,000 miles or 1 year between changes and the filters 6 months or 12,500 miles.

P.S. sorry for th hijack
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Old 02-05-2005, 12:00 PM   #17
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AMSOIL is excellent, as is their filter. Just make sure you don't get their newer budget oil which is rated out to 7500 miles only.

The subies factory suggestion is 7500 for 'normal' driving oci's. With a good synthetic oil and filter you should have no problem going long even with normal 'spirited' driving.

For peace of mind, run the first interval with AMSOIL to 6000, then go 7500 and get it tested at Blackstone Labs.
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Old 02-05-2005, 02:41 PM   #18
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One factor owners often overlook is the percentage of highway miles driven versus city miles. Highway miles are *much* easier on your oil because you are driving a lot of miles all at once where your engine is fully warmed up, running at a steady speed, and not doing a lot of stop light idling like in the city. Repeated bouts of prolonged idling in city driving is very hard on your engine and your oil.

If 70%-90% of your miles are highway, you can easily go 6000-7500 miles between changes using Mobil 1. 7500 mile OCIs was what Mobil used in its famous million mile BMW test. But if most of your miles are stop and go in the city, better to change it at 3750 like it says in the manual under severe service. BTW, if you are running a turbo engine, many top mechanics say you are automatically in the severe service category regardless of how you drive.

Just to make things more confusing , here is a deceptively brilliant oil change formula devised by an Amsoil engineer that will give you a precise answer as to exaclty how many miles you personally should drive between changes. It is theory #5 down the page: Kublin Oil Change Method

(In using this formula, you may notice that as your gas mileage goes up, indicating more highway miles driven, your oil change interval increases significantly.)

P.S. All the opinions expressed in this thread are valid points of view . Good luck with whatever you decide!

Last edited by rexaroo; 02-05-2005 at 02:57 PM.
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Old 02-05-2005, 08:06 PM   #19
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I've have not changed my oil filter in like 7k miles.
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Old 02-05-2005, 08:44 PM   #20
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The oil filter change intervals can be significantly longer than the oil, unless you run a crappy air filter, drive in the dirt, etc. OEM filters will be fine way longer than the oil.
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