'08 Corolla noticable varnish after Castrol GTX

160,000 miles mostly 4k OCI w/ 5w30 dino (typically Chevron Supreme, Mobil 5000 or Formula Shell) and FRAM orange can filters.... but last couple years i started to use more synthetic oils with better filters and longer OCI... car runs great on everything... 90% highway miles last few years.. Had a bunch of Castrol GTX semi-syn high mileage 5w20 (green jug) from a previous vehicle i needed to use up. So last OCI was 6500 miles and 3 months using my own brew of half GTX 5w20 and half whatever 5w30 dino oil i had on my shelf. Oil looked clean enough but i noticed varish around the fill hole i've never seen before. Is varnish a major red flag? What's the likely culprit? Introducing 5w20, Castrol GTX? both? neither? (I dumped it and replaced with M1 HM full synthetic with M1 filter)
 
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with higher miles some deposits are common + conventional as well as almost conventional semi-syn prolly clean less than costlier synthetics, even fake group III as most are!
 
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Interesting you posted this OP. There's the thread about the accord that I asked about Castrol and varnish. If this is the case, I'd probably avoid it now.
 
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Originally Posted by socratestimeless
160,000 miles mostly 4k OCI w/ 5w30 dino (typically Chevron Supreme, Mobil 5000 or Formula Shell) and FRAM orange can filters.... but last couple years i started to use more synthetic oils with better filters and longer OCI... car runs great on everything... 90% highway miles last few years.. Had a bunch of Castrol GTX semi-syn high mileage 5w20 (green jug) from a previous vehicle i needed to use up. So last OCI was 6500 miles and 3 months using my own brew of half GTX 5w20 and half whatever 5w30 dino oil i had on my shelf. Oil looked clean enough but i noticed varish around the fill hole i've never seen before. Is varnish a major red flag? What's the likely culprit? Introducing 5w20, Castrol GTX? both? neither? (I dumped it and replaced with M1 HM full synthetic with M1 filter)
I would not conclude anything until a valve cover is pulled. Fill hole can be deceiving.
 
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Originally Posted by BobsArmory
You might have answered your own question, "using my own brew of half GTX 5w20 and half whatever 5w30 dino oil i had on my shelf."
I don't know what's going on but the mixed oil is not the issue here.
 
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Originally Posted by BobsArmory
You might have answered your own question, "using my own brew of half GTX 5w20 and half whatever 5w30 dino oil i had on my shelf."
Right! That's akin to playing pharmacist then wondering why your homebrews giving you heart palpitations!...‚ Duh..
 
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Well, you have the mileage factor to consider. Getting older has varnished me a little. I don't think mixing oils or the weight of an oil would make any difference. My guts say if there is varnish it would be due to the oil you were using.
 
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Originally Posted by Gebo
Well, you have the mileage factor to consider. Getting older has varnished me a little. I don't think mixing oils or the weight of an oil would make any difference. My guts say if there is varnish it would be due to the oil you were using.
+1 My experience in a very well maintained Buick my father had given me, which was fed a diet of dino oil changed at 3K intervals had lots of varnish, @ half the miles of the OP's. My bet is the dino oil had a big hand in the varnish, and most synthetic oils will take years and/or tens of thousands of miles to clean it up, if it does any real cleaning at all. Some engines are harder to clean than others, and some engines are more prone to varnish than others. So once again blanket statements should be avoided with an oil's ability to keep an engine clean, or clean a dirty engine. It depends.
 
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Originally Posted by demarpaint
+1 My experience in a very well maintained Buick my father had given me, which was fed a diet of dino oil changed at 3K intervals had lots of varnish, @ half the miles of the OP's. My bet is the dino oil had a big hand in the varnish, and most synthetic oils will take years and/or tens of thousands of miles to clean it up, if it does any real cleaning at all. Some engines are harder to clean than others, and some engines are more prone to varnish than others. So once again blanket statements should be avoided with an oil's ability to keep an engine clean, or clean a dirty engine. It depends.
+1.. varnish is just a fact of life. While varnish can shorten the life of some seals by depriving it of proper lubrication, as long as it's not effecting something else like clearances..I say motor on. To me it's just another reason to keep sensible oci's..but to each his own.
 
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Originally Posted by Mad_Hatter
+1.. varnish is just a fact of life....To me it's just another reason to keep sensible oci's..but to each his own.
I salute you thumbsup
 
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Originally Posted by Mad_Hatter
Originally Posted by demarpaint
+1 My experience in a very well maintained Buick my father had given me, which was fed a diet of dino oil changed at 3K intervals had lots of varnish, @ half the miles of the OP's. My bet is the dino oil had a big hand in the varnish, and most synthetic oils will take years and/or tens of thousands of miles to clean it up, if it does any real cleaning at all. Some engines are harder to clean than others, and some engines are more prone to varnish than others. So once again blanket statements should be avoided with an oil's ability to keep an engine clean, or clean a dirty engine. It depends.
+1.. varnish is just a fact of life. While varnish can shorten the life of some seals by depriving it of proper lubrication, as long as it's not effecting something else like clearances..I say motor on. To me it's just another reason to keep sensible oci's..but to each his own.
I agree as well.
 
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Originally Posted by socratestimeless
160,000 miles mostly 4k OCI w/ 5w30 dino (typically Chevron Supreme, Mobil 5000 or Formula Shell) and FRAM orange can filters.... but last couple years i started to use more synthetic oils with better filters and longer OCI... car runs great on everything... 90% highway miles last few years.. Had a bunch of Castrol GTX semi-syn high mileage 5w20 (green jug) from a previous vehicle i needed to use up. So last OCI was 6500 miles and 3 months using my own brew of half GTX 5w20 and half whatever 5w30 dino oil i had on my shelf. Oil looked clean enough but i noticed varish around the fill hole i've never seen before. Is varnish a major red flag? What's the likely culprit? Introducing 5w20, Castrol GTX? both? neither? (I dumped it and replaced with M1 HM full synthetic with M1 filter)
Highway cruising is easy service The varnish you've never noticed, was it because you haven't really looked for it or have you been keeping track and only this time noticed it? Also, the fill was Castrol GTX HM 5W20 plus "half whatever" conventional 5W30, meaning you remembered the GTX and it's grade, and also the type and grade of the remaining whatever 5W30, but not what it was branded? Interesting points: FRAM orange can, GTX in the context of varnish, the 'whatever' 'own brew' mixing oils taboo
 

socratestimeless

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Thanks for all the feedback! Checked my notes... the other half of the brew was 5w30 Chevron Supreme. I'll pull the valve cover to get a better view soon. @ 120,000 i removed the oil pan (to reseal it for gasket leakage) and everything looked spotless from underneath so i think the varnish is new. My '13 Odyssey also has varnish despite M1EP and 8000 mile OCIs but I heard that engine is harder on oil (and I bought that vehicle used).
 
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I'd shorten the OCI and start using some MMO to clean that up. It's got something going on there, and you should nip it in the bud before it gets worse. [Someone had to say it. Some people on here seem to think you need to be able to eat off the engine internals--although in your case, it would appear you could...]
 
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