10W30 Synthetics & Consumption Variation

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I thought I would share my experience with viscosity and synthetic oil brands. I am the second owner of the Lesabre (3.8 Series II) and purchased the car from family friend with only 39k on it. The car has been pampered all its life with the original owner keeping impeccable service records since he is as anal as I am about maintenance. Except for its factory fill, the car has been run on synthetics all its life. GM specifically emphasized in the owners manual that 10w30 was preferred and only indicates trying 5w30 below freezing range of temps. First owner used M 1. I first was using Napa Synthetic (Valvoline essentially) and both of those brands in 10w30 showed virtually no oil consumption over 5k OCIs. When winter came, I thought I would try the 5w30 but that was short lived. On startup, the engine emitted "rattling" sounds and even when warm, the car never sounded quite the same as on the 10w30. Mind you, I have not even heard of BITOG at the time and so I had no built in bias for or against 5w30 oils since my prior car (Honda) thrived on it. This issue with 5w30 happened with Napa Syn and the M1. When I switched over to PP and PPU, I have noted that I even get some oil consumption with that brand's 10w30.

I wonder if part of this issue is due to the relatively "ancient' origins of my engines design. Were tolerances a lot different from engines today? And if so, would that explain why the 3.8 seems to be happier on certain brands of 10w30? I guess I'm wondering if the avg. viscosity of 10w30 oils varies enough to cause what I sense is a lack of oil pressure (from the 5w30 oils) and that even some of my oil loss with 10w30's is due to lower viscosity from some synthetics like the PP? I have decided to try switching over to Castrol 10w30 HM Semi-syn to see how the 3.8 responds to what I hear is higher viscosity range. Has anyone else ever noted oil pressure issues (low) related to viscosity variances amongst oil brands? This car has never been abused and even though I'm not a senior citizen, I drive like one
 
Different formulations can clean rings and other areas which create false seals which can lead to increased consumption which should settle down upon further OCI's.
 
With respect to oil pressure, at operating temperature, most 10w-30 and 5w-30 ILSAC options will be much the same. The 5w-30 I happen to run is thicker at operating temperatures than any 10w-30 ILSAC PCMO on the market.
 
Thanks for sharing das_peikko. My oil loss cannot be attributed to having made a transition to synthetics since it has always been run on those. What was your car's reaction to synthetics sine you say it did not like them? Did you find more oil loss than normal? I must say that the inside of my engine through the oil filler cap looks almost new with no sludge at all. I don't have access to the Chevron, but I can easily find the Mobil Super. Another thing I wondered was whether my valve seals might just be a bit tired given my car is now 20 years old this year. This is my reason for wanting to try the HM version of the Castrol.
 
Hi Garak. Yes, I always assumed that the 30 designation would lead both of those weights to function the same at op temps. My concern with the 5w30 was on cold startups as I sensed that perhaps the motor bearings were not getting the lubrication they needed fast enough. GM updated its oil specs somewhat for the 3.8 when it was reworked for the Series III version.
 
Originally Posted by LowMilesLesabre
What was your car's reaction to synthetics since you say it did not like them?


More oil consumption and engine noise. Conventional oil is totally opposite in those regards.
 
My BIL had the same engine in a Olds Delta 88 and ran 15W40 conventional all year long including winter here in Western NY State along the Great Lakes(meaning very cold). Engine still purrrrrrrr'd like a kitten w/200K miles before selling it off.
 
Originally Posted by LowMilesLesabre
Hi Garak. Yes, I always assumed that the 30 designation would lead both of those weights to function the same at op temps. My concern with the 5w30 was on cold startups as I sensed that perhaps the motor bearings were not getting the lubrication they needed fast enough. GM updated its oil specs somewhat for the 3.8 when it was reworked for the Series III version.

Of course, I have always used a 5w-XX where possible, given what our winters our like. I'm not sure where your temperature cutoff is for driving said vehicle, but, as per SAE J300, a 10w-XX can be pumped down to -30 C, with cold cranking down to -25 C.
 
I too seem to have higher consumption with Pennzoil Platinum as compared to either M1 or Castrol Edge. I have a 2008 Honda CR-V with over 200,000 miles in which I use 5W-20 oils. Over the course of a 5000 mile OCI, I'll probably top off with over a quart to 1 1/2 qts. of Pennzoil. With either of the other two, less than 1/2 quart over the same mileage. I have always wondered if the Natural Gas formulation of the Pennzoil Platinum has anything to do with it or is it because it is on the "thinner" side in comparison to M1 and Edge?
 
I had a 2001 Impala LS with the 3.8 and it used oil between 3000 mile changes running 10W-30 conventional. I didn't notice any leakage. I traded it in at about 35000 miles.
 
Originally Posted by LowMilesLesabre
Hi Garak. Yes, I always assumed that the 30 designation would lead both of those weights to function the same at op temps. My concern with the 5w30 was on cold startups as I sensed that perhaps the motor bearings were not getting the lubrication they needed fast enough. GM updated its oil specs somewhat for the 3.8 when it was reworked for the Series III version.

On "cold starts" the massively high viscosity will be quite similar between a 5W and a 10W unless you are below 0F. The bearings will get lubrication at the same time assuming the oil can be drawn into the pickup tube.
 
I had a 1990 LeSabre and that recommended 5W-30 year round, they did go to 10W-30 then came back to the typical GM spec of 5W-30 for the period prior to Dexos. I ran both 5W and 10W-30 and noticed no difference, mainly Havoline conventional and MaxLife blend. I'm not sure if the "rattling" was the result of the weight or the synthetic base oil, but M1 5W-30 tends to be thicker at temp than most 10W-30's.....
 
Hmm.. I have owned four 3.8's over the years, all of them run on 5w30 M1 changed at either 7500 or 10000 kms intervals. The only issues I've noticed are a 'dry' sounding start if the car had been sitting for more than a week, and slightly noisy lifters after an oil change. The lifters get quiet again after a few hundred kms or so. Had good service from all of them, the engines were running great while the rest of the car was needing repairs due to high mileage (300000 kms plus).

Edited to add, I bought three of the four with less than 60000 kms, so most of their oil service history was as described above.
 
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Originally Posted by Garak
With respect to oil pressure, at operating temperature, most 10w-30 and 5w-30 ILSAC options will be much the same. The 5w-30 I happen to run is thicker at operating temperatures than any 10w-30 ILSAC PCMO on the market.



That is pretty much what I have read . 5W-30 & 10W-30 are ~ the same viscosity as " normal operating temperatures as straight 30 weight oil .

Please correct me if I am wrong .

We own a 2006 Buick 3.8l and if I recall , it indicated 5W-30 , but does not mention DEXOS . So far , I have used name brand conventional oil ~ 3000 mile OCI .
 
Originally Posted by LowMilesLesabre
Hi Garak. Yes, I always assumed that the 30 designation would lead both of those weights to function the same at op temps. My concern with the 5w30 was on cold startups as I sensed that perhaps the motor bearings were not getting the lubrication they needed fast enough. GM updated its oil specs somewhat for the 3.8 when it was reworked for the Series III version.



Can you please expound on those changes ? Our 2006 3.8l Series III only has 40,000 something miles on it . About due for an oil change ( does not get driven a lot ) . Plan on using 5W-30 conventional Mobile and ever which brand of filter I ordered from RockAuto.com . Next oil change , after that , will be Shell 5W-30 conventional I purchased on sale at Home Depot , a couple of years ago , for ~ $ 10 a jug .
 
Originally Posted by WyrTwister
We own a 2006 Buick 3.8l and if I recall , it indicated 5W-30 , but does not mention DEXOS . So far , I have used name brand conventional oil ~ 3000 mile OCI .

Technically, that's one place where GM tends to make some good sense. You call them for that vehicle, they'll say use a 5w-30 dexos1, which will be back speced for darn near everything.
 
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