Which would you choose? 12k mile OCI with a 100% synthetic or 5k mile OCI with conventional

Joined
May 21, 2018
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South Carolina
I service my vehicles at 1 year or 5k miles using, in the past, SuperTech Synthetic, and now, SuperTech Blend. Your engine is going 5 times further on a quart of oil than manufacturers used to recommend (1 quart for every 1k miles).
I'm not on the 10k oil change interval mind, yet. ;)

EDIT: I use factory filters.
 
Joined
Dec 2, 2021
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Lake County, IL
In an average vehicle under average conditions, I'd be OK with either, really. If I had to choose, I think I'd go for the premium oil. For myself, I tend to split the difference and change my run of the mill synthetics and filters at about 8K.
 
Joined
Jan 25, 2003
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Decatur AL USA
I
The answer is "it depends."

I'm perfectly comfortable with a 5,000 mile OCI with a typical SN conventional oil and a typical (eg WIX) filter on my Accord V6. But I would never have done that with my BMW.

The BMW oil monitor was okay with a 25,000 km (15,000 mile) OCI with a very good synthetic oil and a very good filter. But the shop foreman at the BMW dealer suggested I change the oil at half that interval to protect the valve train if I was going to keep the car for the long run. So that's what I did, but I did leave the filter for the full 25,000 km. So I wouldn't have been completely comfortable with option 1 for the BMW, unless there was a lot of highway driving, though the BMW manual and the oil monitor would have both said it was okay.

I've seen those cars tore down that looked very good with longterm 15,000 mi OCI on BMW Oil and I've seen them that looked not so good. I think many knee-jerk react to the OCi length when other things are going on.
 
Joined
Feb 19, 2007
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Maryland
I would need a used oil analysis on each oil before coming to a final answer. I would sample both at 5000 miles, then the full synthetic again at 8000 and 11000 miles (provided the 5000 and 8000 mile analyses were good).
 
Joined
Aug 30, 2016
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Midwest
The one I choose is full synthetic on a sunny day in April and again in October on a sunny day. Usually runs between 4200 and 7154 miles. Yah I know I'm over caring for the Corolla. But then that may be one of the reasons I've been driving it for 16 years without major issues!
I have a 2005 Toyota Corolla with 95,000 miles. I change oil the same as you. I think it will rust out here in Chicago before the drive train goes. It's been a great car and my insurance is dirt cheap.
 
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Pacific Northwest
It is going to totally depend on the vehicle in question. My 51 Chevy truck gets a fresh pan full of 10w30 every 10 years or 3000 miles, which ever comes first. 7.3l PowerStrokes are always 5k or less (no stiction issues yet). The wife's 5.4 Triton has lasted for over 200k with happy stock cam phasers due to religiously consistent sub 5k changes.

No super premium synthetic oil would allow any of those vehicles too thrive as long with 12k changes in my estimation. Corollas and Civics are another story.
 
Joined
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Wet side WA
I have a 2005 Toyota Corolla with 95,000 miles. I change oil the same as you. I think it will rust out here in Chicago before the drive train goes. It's been a great car and my insurance is dirt cheap.
Well here on the wetside in Washington they use very little salt on the roads. Rust isn't a problem for me its the wife wanting a new car after only 18 years. I'm sure the thing would go 300K with few issues but at less than a month away from 78 I don't feel I'm going to ever get the Corolla to 300K. But I'm willing to give it a try!
 

KJH

Joined
Oct 15, 2011
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143
I didn't want the post to become too convoluted and too much to read.

More information:
I drive a 2009 Toyota Prius with 183k miles on the odometer. It burns about one quart every 5,000 miles. These cars are notorious for the piston control rings becoming clogged, resulting in some burning oil. I don't consider the amount of oil consumption too bad right now, but wondering if some of my more recent extended oil change intervals of about 12k miles with good quality oil may have played a factor in the reason it is now burning oil and has some varnish visible at the crankcase fill opening. I keep a good record of my oil changes, and I've only done these "long" (10k+) OCIs about 6 or 7 times. Average OCI over the life of the engine is 7k miles. Currently pondering whether to continue the extended OCI approach or adopt a shorter OCI plan of no more than 5k miles.

IMO extremely likely that the long OCI was contributing factor to oil burning from gummed up rings. See it over and over with many 4cyls made in the past 10-15 years.

Most evidence shows that long OCI will not cause premature wear. But in alot of newer 4cyls that are hard on oil, it does seem to make stuff dirtier in there. That doesnt really matter on its own, but in many cases it does appear to gum up rings and cause oil consumption.
 
Joined
Sep 14, 2015
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ne & sw
5k semisyn or 10k syn oci. nothing fancy, api sp house brand oil & decent filter is fine. i lean to 5k as it would force me to keep a closer eye on life under the hood.
 
Joined
Jun 8, 2016
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Texas, USA
I think in this case I'd have to run the risk of using conventional at 5K. Fuel dilution and carbon contamination would be too high for my liking at 12K.
 
Joined
Jun 15, 2020
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Aitkin,MN,USA
5k with synthetic
My 2005 Montana Sv6 195000 miles does not like 5w30 magnetek full synthetic..wix xp. Lifters click when cold..any conventional oil ILSAC 6A WITH standard (5000 MILE) wix never started with noisy lifters mostly FVP 5W30. I m draining the Castrol synthetic early (5000 miles) and putting conventional 5w30 and std WIX FILTER back in it. Engine uses a qt every 3000 miles on synthetic and conventional oil. But the conventional has no lifter sound ..engine cold or hot
 
Joined
Sep 17, 2007
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B.C Canada
Synthetic at manufacture recommended intervals. Or B if you’re not planning to own the vehicle until the wheels fall off. For me if I’m buying a vehicle to own for the long haul, I would rather spend a few extra $ and put the better oil in it.
 
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