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Buliding oil pressure upon start up after recent oil change - do I have an issue?
Question for the community -
C5Z / LS6 - recent oil change to Mobil 1 0w40 plus ZDDP additive for upcoming track dates in the heat. Once complete, on the first and second start up I noticed the dash oil pressure gauge takes a few seconds to build up to normal idle PSI, ~ +/- 45 PSI. It's the middle of summer, so the cold oil temp at rest is in the 90s.
Do you think I have an issue? Am I getting momentary oil starvation? Is the 0w40 too thick? Or is it just the normal C5 dash electronics catch up to the engine's PSI?
IMO you have oil that is too LOW viscosity for start up. That's why it's taking more time to build pressure.
I run 10w/30 in socal.
0 weight maybe good for starts in the winter in Fargo.
The 40 is the hot temp. viscosity (think 225-280 deg f) which you maybe will get to on the track or a long pull up the Grapevine or when the engine is really working hard.
Meanwhile every time you start the car you are getting a little extra wear on engine parts due to low/no oil pressure.
I would rethink putting 0 wgt in an ls6.
BTW I have lab tested my oil (Blackstone) and the numbers were excellent.
Just for fun I checked my oil pressure from an overnight cold start today. I counted one - one thousand, two - one thousand, you know to approximate seconds.
Hit the starter and as you know the needles sweep, and at two seconds coming back to the left from the right sweep it settles at about 36-38 psi & then by the third second it settles at 42 psi on a fast start up idle.
Don't go by the digital too much lag.
As I drive off & if I let it climb in the hood to maybe 4k rpm it'll get over 60 psi.
So good pressure with 10w-30, I would use that or if you can find full synthetic that's 10w-40 I would say that's ok too.
But not the zero wt for ls6.
Have fun tomorrow & be safe. I instruct with BMWCCA tomorrow at the stadium.
Using Mobil 1 as an example- 0w40 has a higher viscosity than 5w30, even at room/ambient temp. The labeling/numbering on the label can be a little misleading sometimes (this surprised me at first). Take a look at the actual specs on their website:
For what it's worth I run 5w30 high mileage, which is a tad thicker than standard 5w30 and has the same zddp package as the 0w40 etc. As I get faster and see higher oil temps I might move up to a 40 wt, or get an oil cooler, or both, we'll see.
Also generally speaking the thinner the better at startup/cold start. You can see from the viscosity numbers above that cold thickness is at least 5-6x that of @ operating temp. Especially for a street car that will have lots of cold starts, short trips, etc. Mine's a weekend and fun car, so I go for middle of the road and don't sweat it too much.
I think what you describe OP is standard behavior and same as what I see. When I did heads/cam swap, I pulled the injector fuse and cranked it for quite awhile to ensure good oil pressure at first startup. Even then, the it took a second or two for the gauge to "come alive". I'd keep running the oil you have, I used it for my last track day. Only way I'd go thicker is if you start seeing high oil temps like 280... which you might being summer and all.
Using Mobil 1 as an example- 0w40 has a higher viscosity than 5w30, even at room/ambient temp. The labeling/numbering on the label can be a little misleading sometimes (this surprised me at first). Take a look at the actual specs on their website:
For what it's worth I run 5w30 high mileage, which is a tad thicker than standard 5w30 and has the same zddp package as the 0w40 etc. As I get faster and see higher oil temps I might move up to a 40 wt, or get an oil cooler, or both, we'll see.
Also generally speaking the thinner the better at startup/cold start. You can see from the viscosity numbers above that cold thickness is at least 5-6x that of @ operating temp. Especially for a street car that will have lots of cold starts, short trips, etc. Mine's a weekend and fun car, so I go for middle of the road and don't sweat it too much.
I think what you describe OP is standard behavior and same as what I see. When I did heads/cam swap, I pulled the injector fuse and cranked it for quite awhile to ensure good oil pressure at first startup. Even then, the it took a second or two for the gauge to "come alive". I'd keep running the oil you have, I used it for my last track day. Only way I'd go thicker is if you start seeing high oil temps like 280... which you might being summer and all.
Two questions & thanks for the post.
1) How would you attempt to explain the op's real life change in getting oil pressure, directly related to his oil weight change?
I will take one guess - different oil filter???? Or if the zero wgt is in fact thicker, then yeah that would explain slower oil pressure build, molasses does not flow as quick as water.
2) If those tables are correct (and I have seen lot's of typo's in my time) that has got to be THE DUMBING F^#*&!G thing ever that 0w-40 is thicker at startup than a 10w-anything oil. What in the hell are they thinking of at Mobil???? To label it that way???
Oil filter sounds like a decent possibility... don't have enough personal experience to really comment on that one though. I haven't looked that much into it. I have no idea what kind regulations or standards are used to define the numbers on the bottle, but I found this whole thing a bit eye opening as well.
Here's their high milage variety for comparison too. You'll see that the standard 0w40 is significantly thinner at 40C but not much thinner at 100C...so overall it's a good oil and I can see why it's a popular dual purpose, regular, off the shelf oil.
Really not enough info in the original post to speculate much further... he doesn't say that it's taking longer than it was before for the oil pressure to come alive. Maybe just watching the oil pressure gauge more closely than normal with the thicker oil, but it's been that way all along. I watched mine today after a 1-2 week sitting and it took a second for the gauge to do anything, so either way I think his behavior is normal.
Hope this helps...and I agree the labeling is very strange and even misleading at times. There might be a reasonable explanation, but I haven't dug into it.
Buliding oil pressure upon start up after recent oil change - do I have an issue?
I should also add I've ran regular M1 5w30, the high mileage variety, and M1 0w40. The 0w40 was the thickest/highest oil pressure of the bunch. Both hot and cold pressure.
So I dug into this SAE J300 document. The number before the W really pertains to sub freezing temps. Not at 40 C or whatever typical outside temp might be around you. The 0w40 then should actually be thinner at extreme low temps vs 5w30... But not 40+ or maybe even 0+... Who knows. Guess I never dug into the really cold stuff because I live in FL. Here's a table from SAE J300.
I also do not pay any attention to viscosity at below zero or even below 32 f temps, has no relevance to socal conditions.
Interesting discussion.
I've never run anything other than 5w or 10w full syn in my ls6 motor.
Knock on wood, good Blackstone results. 60k miles.
Could very well be the 0w is ok/good to use. Just never tried it.
But if it's true that it takes longer to get pressure on a cold start (say 60 - 75 deg f) then that's not a good thing. A LOT of wear happens at cold start has always been my understanding.
Sorry for the delay, was at the track all day yesterday. To answer a couple of questions, I'm using the same model Mobil 1 filter and I did fill it with oil before replacing it. Also, I can't say with 100% certainty that the oil pressure came up quicker, but it sure seems that way from memory. I am watching the analog gauge and it takes about 2.5 seconds to come up to top operating PSI.
08-29-2015, 02:30 PM
Buliding oil pressure upon start up after recent oil change - do I have an issue?
