Varnish with Synthetic Oil question

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Cook the oil, you mean accelerated thermal breakdown due to running the oil warmer than normal operation? I'd put that with track use and towing.
I guess I'm thinking more of my personal example, my 84 Cutlass has an aftermarket aluminum rad and in extreme heat when stuck in traffic (like waiting to cross the border coming back from Syracuse nationals car show), temps crept up to 220+ before I turned off the AC and started bringing up rpm to cool it down.

Or about 5-6 years ago the cooling system got really dirty and needed a flush. Before flushing it would get to 230 on the highway, which actually destroyed the starter before I got to the flush.

Or when I had electric fans on a toggle switch and forgot about them until hitting 260 climbing a steep hill in a campgrounds. (eventually switched back to a stock clutch fan - hence the shroud issue now in hot weather).

Not exactly problems your typical trade every 10 years consumer would have but if you drive a "hooptie" for multiple decades these things can happen.

So, yes you're correct, if everything remains in perfectly ideal conditions, no towing, abuse or other mechanical factors at play, conventional oil will hold up fine.
 
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oil temps tend to track more with rpm than with coolant temps if both circuits are seperated. Newer cars have interchangers so the temps are closer together. But even 260F isn't dangerous for the oil yet if it's thick enough It's getting there for the coolant though depending on concentration and pressure
 
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oil temps tend to track more with rpm than with coolant temps if both circuits are seperated. Newer cars have interchangers so the temps are closer together. But even 260F isn't dangerous for the oil yet if it's thick enough It's getting there for the coolant though depending on concentration and pressure
I would add to this that in modern engines the coolant systems are more capable of handling temperatures due to fans etc....where as oil capacities are lower, and oil coolers (if any) are normally passively radiated, so not as efficient as keeping oil temperatures in check. Synthetic oils are much more capable of handling higher temperatures.
 
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interesting reading! i tore my 72 chev nova 307 oil drinking engine down for a rebuild at under 80 thou using a qt in 500 miles. i mostly did short drives used conventional Valvoline 10-30 oil, prolly 3 thou changes with filter of course. the inside of the engine was SPOTLESS!! just the opposite is when i tore down a strangers small block chev at my friends business + filled a POUND coffee can with SLUDGE i cleaned out before the hot tank. i jokingly asked the stranger did you use Pennzoil + he said YES, how did you know!! of course i knew not his service habits or not!!! sure hope its better now because i use its sister QuakerState ultimate durability 10-30 synthetic now! as noted lots of variables even in todays engine builds with modern machinery!
 
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interesting reading! i tore my 72 chev nova 307 oil drinking engine down for a rebuild at under 80 thou using a qt in 500 miles. i mostly did short drives used conventional Valvoline 10-30 oil, prolly 3 thou changes with filter of course. the inside of the engine was SPOTLESS!! just the opposite is when i tore down a strangers small block chev at my friends business + filled a POUND coffee can with SLUDGE i cleaned out before the hot tank. i jokingly asked the stranger did you use Pennzoil + he said YES, how did you know!! of course i knew not his service habits or not!!! sure hope its better now because i use its sister QuakerState ultimate durability 10-30 synthetic now! as noted lots of variables even in todays engine builds with modern machinery!
Oh wow Pennzoil still causing sludge in motors this ain’t good at all
 
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look what pennzoil dod to mynwifes engine! sludge city
IMG_3029.jpg
 

OilUzer

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it was a joke. the engine has 125k. i think its very clean

ok I see. 😆 my bad. you are kind of new here and we are on the internet so I wasn't sure if you were concerned about some varnish or not. Some people here like or expect nice & shiny engines with 300K+ miles on them! lol
 
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ok I see. 😆 my bad. you are kind of new here and we are on the internet so I wasn't sure if you were concerned about some varnish or not. Some people here like or expect nice & shiny engines with 300K+ miles on them! lol
we just got this suburban used a couple months ago and ive been running pennzoil synthetic since. idk what the last guy did. but i can tell you the first oil change got very dirty by 3k so it may be in the process of cleaning up. not sure
 
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what oil(s) and intervals have you been using?
The truck is an '03 Silverado SS, 6L LQ9 engine. Previous history and service unknown. She's had 4, Mobil-1 full synthetic changes since my acquisition. Depending on season, it flip flops between 5W-30 EP & 0w-40 FS eurocar.

I follow the OLM. (It triggers anywhere from 6500~7500 miles) The first 3 OCI's were filllllllthy. A new Fram Ultra spun on each time for crud catching.. I had the valve covers off for new gaskets and grommets, replaced a seal for the oil cooler bypass hoses tucked up over the filter boss. I was just killing seeps and weeps. She doesn't seem to consume a drop otherwise. Changed the oil for seasonal 0W-40 and a new WixXP filter this time, got a good oil+filter combo deal @ local O'Reilly's that knows me and treats me pretty good.

She had 180k miles on the motor when the covers were pulled, the photo I linked is untouched, the valvetrain as it was, no cleanup.
I'm sold on the manual instructions, they recommend the SS models essentially be fed Mobil-1 like a Corvette, full synthetic only.
 
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The truck is an '03 Silverado SS, 6L LQ9 engine. Previous history and service unknown. She's had 4, Mobil-1 full synthetic changes since my acquisition. Depending on season, it flip flops between 5W-30 EP & 0w-40 FS eurocar.

I follow the OLM. (It triggers anywhere from 6500~7500 miles) The first 3 OCI's were filllllllthy. A new Fram Ultra spun on each time for crud catching.. I had the valve covers off for new gaskets and grommets, replaced a seal for the oil cooler bypass hoses tucked up over the filter boss. I was just killing seeps and weeps. She doesn't seem to consume a drop otherwise. Changed the oil for seasonal 0W-40 and a new WixXP filter this time, got a good oil+filter combo deal @ local O'Reilly's that knows me and treats me pretty good.

She had 180k miles on the motor when the covers were pulled, the photo I linked is untouched, the valvetrain as it was, no cleanup.
I'm sold on the manual instructions, they recommend the SS models essentially be fed Mobil-1 like a Corvette, full synthetic only.
i used to run only mobil 1 0w-40 but it hasnt been at mynwalmart for a good price in a while until this week. i may switch back to it next time.

i think synthetic oil is a must with these engines. otherwise you will end up pulling the heads to change rattling lifters.
 
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i used to run only mobil 1 0w-40 but it hasnt been at mynwalmart for a good price in a while until this week. i may switch back to it next time.

i think synthetic oil is a must with these engines. otherwise you will end up pulling the heads to change rattling lifters.
The manual states for my model year that non-SS models use a semi-synthetic for full OCI. (If I remember correctly) A complete oil change at OCI indicated by OLM and a filter swap.

It's then footnoted*

*You may use semi synthetic in SS models for a reduced OCI period of about 50% of indicated oil life, not to exceed 3000 mi./6months.

Either way, I've not known any GM to suffer under periodic, by the book oil services with synthetic oil and filter change. Only caveat I have of course is if the book calls for a Dexos certified engine oil, use that instead and steer away from Dexos semi synthetic. Go full bore. My '13 flex fueled Impala 3.6 seems to thrive very well on Mobil-1 5W-30 EP Dexos and plain old E-core Champion Labs/Delco filters.

My previous '95 T-10 Blazer 4.3 Vortec was flawless and clean on the old Castrol German green elixir and NAPA gold filters after a few, fast back-to-back OCI's w/Rotella and ACDelco filters. Once the goop was gone, synthetic kept her "I'd eat off her!" clean even inside the throttle bore. ^.^

Just keep it fresh, changed, full...and faggeddhabouddit.
 
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Very clean with 180K miles!
Is this engine easy on oil in general?
It's an iron block version of an LS-III w/aluminum heads. So I would *guess* by nature that it would be. I'm sometimes not gentle on it however...Summer sees plenty of hauling and stop-light rips. ^.^ Time and further age will tell.
 
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I run the 0w40 m1 in my 4.8 LS truck engine. I think it's a good choice in there engines and I was able to buy it for $30/5L jug (Canadian) so I had a small stash. Finally ran out and Pennzoil euro 5w40 is going in this weekend for a change. That's what was on sale when I needed it.
 
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