Whaddya guys think?

Yeah, I know exactly what you mean, and it's a good thought. I also liked El Diablo's idea on the bypass spring mechanism. It's gotta be one of the two, or a combination of both. I'm 99.9% certain it isn't the lifters as if it was, the noise would be there on every cold start, not just the first 5 or so. Weather has been pretty much the same, although now it's getting colder, and yes, I fill em' up before I install.

Thanks for the brainpower!

Doc

Mobil 1 10W30, which I've been using in it since I got it.

Doc

What's the first thing you do when changing the oil? I always pull the dipstick and the fill cap on the valve cover. That lets air in so the oil doesn't blurp out, making a mess when I drain it. What I'm getting at is a stretch, but what if draining the oil is creating enough vacuum in the block to pull the oil out of any marginal lifters. That 'could' explain the noise and the relationship to oil changes. H

Shouldnt the bypass work only if the filter was plugged or maybe if you use thick oil in the winter........? M1 10-30 wouldn't bypass even when very cold I don't think. Could be a check valve in the new filter "breaking in". I wonder if the AC filter has a stiffer check valve or maybe the M1 doesnt have one at all?? If you ever figure it out please let us all know. I never have cut open an oil filter to see the guts, but now I'm kinda curious.

Not possible as the crankcase isn't sealed tightly enough to create any type of vacuum during an oil change. There is a wide open breather line (drivers side valve cover), so even with the oil fill cap on there is still airflow to the crankcase.

Doc

Ehhhhh, that was a typo, meant to say check-valve, not bypass valve, sorry. You're right, even at 20* M1 10W30 flows pretty smoothly.

Yeah, that's kinda what I'm thinking.

Doc

Are you using M1 5w30?

I used it in an old truck of mine for 90K miles - I'll never use it again due to that motor's life being cut very short. No, I can't prove the oil had anything to do with it - I'm just not taking any chances.

I've read a few things about it - it's barely rated 30w. It's horribly thin. The other is that it gets "better" with age (mileage). Apparently it's lubricity (is that a word?) isn't good until the oil has a few thousand miles on it.

Let me try to dig up those sources.

-marc

All the onfo I've ever read on M1 5w30 lead me to believe it was on the higher scale of 30. I've used it in alot of vehicles without issue. When I buy a vehile I'll switch it over to M1 and run the first change for 3,000 miles. Man you ought to see the oil after that first 3,000! It's usally pretty nasty looking because it cleans out alot of the sludge that dino oil has left. After that first change I run 6,000 miles between changes. According to oil analysys, I could go way longer than 6,000 but I figure what the hell, it's cheap insurance. Plus, I can change my oil and rotate my tires at the same time (6,000 mile tire rotations).

I've never heard of M1 causing premature engine failure. What kind of engine was it? I only use 5w30 on lower mileage vehicles that call for 5w30. On older vehicles or vehicles with over 100,000 miles on them I use M1 10w30.

-T> >

Yeah, I saw a test where someone ran M1 5w30 up to (I think) 18,000 miles before they decided to change it out. The oil anaysis said it was still okay for a little while longer. That's insane. That's the test that indicated the oil got 'better' with it's age...

Mine was the 4.3 V6 - 2000 Blazer. I change the oil every 5K. The motor started to really lack power on the highway when it got up there in age. At 90K miles, it was burning almost a quart a oil change. At 95K miles, I started it one cold morning and thought a rod was going to come out the pan - I've never heard a motor rap so loud and stay together!

The stuff I was reading about was all in the GenIII motors. Mostly high performance (6000+RPM) LS1 stuff. Everything I've read indicated that 5w30 was generally too thin for heavy duty or high performance use.

I really gotta dig up that info... I read it a while back...

Anyone who runs 5W30 in an 8-cylinder at 6+K RPM is just begging for failure.

Doc