Oil switch for GM 3.4L and 3.5L

[mechanicx]

Hardware Monk is hard for me to make much sense of the noise you are hearing and how a thinner oil helps hot running noise if it was a bearing noise. I'm not sure that a thicker or even a lighter oil for that matter would quite piston slap much. I'm not really sure why you are getting such different results from different oils. But the poster that mention the timing chain might have spotted the issue. Although vin 6 is a the 5cyl I think and the V6 3.5 has no balance shafts.

Anyway, I don't consider GM switching to 5W30 as being lighter because before that they used 10W30 also a 30 weight. Anyway, I don't tend to like Seafoam. I would suggest you try some MMO and see how it does. I think PP 5W30 and some MMO oil would be a good way to go. And if that doesn't solve the noise issue. I wouldn't worry about it or just search for the mechanical reason for the noise.

 

[Hardware_Monk]

Captain_Klink - I reference top mechanics and automotive machinists, because they get to see, and have to deal with, the real world results of what engineers decided were their latest and brightest ideas once.

Oil isn't the best line of defense, its the only line of defense. The thinner you make that barrier, the easier real-life variables can break through.

Yes, it needs to be thin enough to get everywhere its supposed to, but in my experience, not one bit thinner.

Also, as a side note - By contrast to the usual oil change rules, there is a fellow in the area who operates his vehicles like he did the aircraft engines he was responsible for in military service: Never, ever, change the oil, just change the filter religiously every 2000 miles, and top up the crankcase as needed. With several hundred thousand miles, it ran perfectly quiet and was as strong as ever. Go figure.

mechanicx - You're right, by the numbers 5w30 isn't far removed from 10w30, but more importantly, back when 10w30 was spec, nobody I knew, or heard of, used it for anything except for:

1. New vehicles, maybe the first 10-15,000 miles
2. Winter weight oil in the coldest weather
3. People who didn't know any better
4. People who insisted on saving $0.10 per quart on oil

Engines always ran better, were much quieter, and lasted alot longer with 10W-40 at least, or whatever suited the miles and wear. Whatever, it doesn't matter now.

Yes, it is a puzzle to me as well, its sensitivity to oil weight vs temperature, and the pattern of its noise.

For the most part, what I am hearing is piston noise. I think when the oil weight vs temperature is right, the cylinder walls get maximum flooding from what its able to pump. This is enough to eliminate noise from what must be pistons that are now on the loose side, having removed the deposits on them (best guess) by switching to synthetic.

Why it has trouble pumping even factory weight oil when it gets near freezing, I don't know, and I literally can't afford to find out. I broke my own rule about buying a car I can't afford to tear down.

The other noise I mentioned, a low frequency idle noise (only when using the heaviest weight oils or hitting lowest temps) makes me think of mains that aren't being supplied properly. That brings it back to having trouble pumping oil that's even a little too stiff (for its current internal condition).

The vehicle does so well when the temperatures are above 50 degrees, it doesn't seem like the same vehicle. Its quiet, and everything is happy. Must be the oil moves well enough, and the pistons are hotter, getting tighter and staying straighter in their bores.

Going down the temperature and oil weight scales, I think I'm just maintaining the (extremely narrow) viscosity window its happy with.

Short of internal mechanical issues I can't afford to fix, the shedding of internal deposits could have partially blocked or jammed (which has been suggested) something in the oiling system.

That was why I tried Seafoam. Auto RX has been mentioned as a cleaner, and you mention MMO. Being new to the forum, I'm not up on all the abbreviations. What does MMO stand for?(sorry to have to ask).

Also, I was putting cleaners last, since the oil seems to stay quite clean visually now. Would they remove dino oil deposits that all these synthetic changes would have missed?

Thanks all, for the input on this.

 

[il_signore97]

^Just have another thought for you...

The low frequency noise at idle with the thicker oils and/or with very cold temperatures is most likely not one of the mains. You will most definitely know if the mains are being starved.

The noise you hear at idle on a hot engine with thicker oil is just one of the hydraulic lifters. I've had this noise once on my Chevy Venture before when I shoved in an HDEO 15W40 for a trip that I had to take.

Basically, this was way back at around 110,000km (65,000 miles) when the lower intake manifolds started leaking coolant into the engine. Due to a funeral, we were forced to take the van on a 1000 mile round trip before I had a chance to fix the coolant leaking into the crankcase. So I used the 15W40 diesel oil as a last resort to help "protect" the engine as best as it could for the duration of the trip.

Turns out the van was fine, gaskets were replaced, and it has 220,000 km on it now with no noises or leaks at all. The low-frequency lifter noise went away as soon as I changed back to a normal oil weight (0W30). It just makes a minor piston slap noise for roughly 15 seconds on cold days after a cold start. Not bad for a van that tows a trailer all the time and was subjected to extremely short trips for its entire life.

 

[mechanicx]

MMO is Marvel Mystery Oil. It has some lubricating properties and good cleaning ability. It sounded like to me you needed a thinner oil to combat the noise and not thicker, plus maybe some cleaning. Pennzoil Platinum 5W30 and some MMO which will maybe thin you down to about a 5W20 seemed like a good option to me.

 

[Hardware_Monk]

Thanks! That's been an old favorite for alot of people, and sounds like a good option for the next change, used carefully.

The straight 5W-20 Syntec in it currently is fine for highway cruising, and temperatures near 32 or lower. We going into some colder weather, so its OK for now, but I think something midway between would be better for more all-around use, "by the sounds of it"...

I thought about a mid-range mix for this last change, and had two weights purchased to do something like Capt Klink uses, but the 14 degree nights we had at the time made me default to straight 5W-20.

We'll see how it goes.

 

[Hardware_Monk]

After some varied temperature conditions, I added a half quart of Lucas Synthetic Oil Stabilizer to finish filling the crank case. That's half what the bottle says to use, but more would have been way too thick, even with 5W-20, for this engine, in this weather.

It has worked out very well, in temps from 7 to 28 degrees. Cold starts aren't very loud, and are quiet very quickly. Idle noise is reduced, and is only occasional.

The noise under light acceleration is almost non-existent, but I also made one other change that may have helped that. I noticed when gently raising the RPM's in neutral, that it had a definite beat to it, not quite a miss, around 1300 RPM.

New plugs were put in recently, the compression was checked at that time, and all was fine. Plug wires didn't show signs of grounding or cross-firing, so I figured it was most likely a sticky injector.

I've used injector cleaner on it before, but this time I used Berrymans cleaner in the recommended amount. It seemed to smooth out most of the beat. Regarding piston noise, if a sticky injector or two had been washing cylinder walls with too much fuel, it could make them sensitive to how much oiling they received, I would think.

Whatever the reason(s), the motor has seemed pretty happy, even at these temperatures. Warmer weather is forecast for later this next week, so I'll see how far up the temperature scale this mix will go.

Syntec 5W-20, half quart Lucas Synthetic Oil Stabilizer, AC oil filter.

 

[el_zorro]

Originally Posted By: Hardware_Monk


Oil isn't the best line of defense, its the only line of defense. The thinner you make that barrier, the easier real-life variables can break through.

Yes, it needs to be thin enough to get everywhere its supposed to, but in my experience, not one bit thinner.

Also, as a side note - By contrast to the usual oil change rules, there is a fellow in the area who operates his vehicles like he did the aircraft engines he was responsible for in military service: Never, ever, change the oil, just change the filter religiously every 2000 miles, and top up the crankcase as needed. With several hundred thousand miles, it ran perfectly quiet and was as strong as ever. Go figure.



I agree with your thicker is better for protecting engines idea. The only reason for the trend to thinner is for fuel economy. However, your military airplane mechanic friends strategy probably ended up in thinner oil always by not changing it. As oil breaks down it gets thinner and then eventually combusts. The other thing is what works well for aircraft engines may not work well for car engines. The old military radial engines were designed to consume a lot of oil. They had oil tanks that had to be filled each time fuel was added. Even sitting on the tarmac you can see a lot of oil dripping out from these engines.

 

[Hardware_Monk]

el_zorro: Yes, some of that occurred to me, and its nothing I'd try at home. I remember reading about a fellow on a military prop transport to the other side of the Pacific who went up to tell the pilot about a stream of oil he had been watching running out of one engine. The pilot asked "Is it still leaking?" and he replied that it was. The pilot said "Good! That means we've still got some!"

As to the Maxx 3.5, I'm still running the same oil mix. It hasn't broken down yet, and although it doesn't do everything perfectly, any noises it makes are relatively muted, and some days it's pretty quiet. Considering the extreme spread of temperatures we've been seeing, I'll settle for what its doing currently.

When we move out of the low extremes, I'd like to try the 5w30 with some Marvel Mystery oil to thin it a little, as opposed to the 5W-20 with a bit of Lucas thickener that's in it now. 28-30 degrees seems to be the top of its comfort spectrum, currently.

Also, I do think that AC oil filters make for more quiet cold starts with this engine, as someone suggested previously.

 

[Hardware_Monk]

The Maxx oil mix was about done when the extremely cold weather broke, so I went with PP 5w30 as a baseline, and an AC oil filter.

There were repeated short warming cycles that kept me from committing to thinning it with Marvel Mystery oil. In the end, I think it sheared down a very little bit, and worked well enough in the mixed temps we had.

Last time I checked it (at 3000 miles) there was still decent base lubricity between thumb and forefinger, even though it seemed a tiny bit thinner than it was initially. It wasn't dark brown or tinted yellow yet, either.

That's not a bad performance. If the weather had stayed colder it should have been thinner, though, I think.

The 3.4 Venture is back in service. Way back, I mentioned that (after sitting for several weeks in the fall) it had a very noisy start-up with a dusty cloud out the tail pipe. Subsequent start-ups became much quieter, very quickly.

A high-mile Cavalier purchased last fall did the very same thing, after about a 5 weeks of sitting. Neither vehicle spouted any blue smoke at that time or any other.

Eventually, I concluded that it must have been carbon-based deposits that absorbed enough moisture to soften and come loose, blowing out in a cloud.

That conclusion seems to be valid, since now that its back on the road, all the hot operating noises have disappeared. The only thing that remains is the a general flurry of start-up clatter when dead cold, and that fades in 20-30 seconds depending on temperature.

Its dead quiet if fully warm on re-start. The only odd note is a partially warm re-start is louder than if it was dead cold... but whatever...

Following this good news, I planned for a short oil change, and put in some inexpensive Carquest store brand 5w30 Synthetic, with a Mobil One filter I had left from an "oil-change sale" last fall.

I plan on changing it fairly soon, both because it was in storage, and because it had the "blowout" of deposits. We'll see what temps are like when I change it next, but at present the 5w30 synthetic is working fairly well with our daytime temps in the low to mid 30's.

 

[wolfc70]

Glad you are getting this sorted out. The 3.5 should be a fairly quiet motor, although I have heard of a few with piston slap.

The 3.4 is a different beast, they will make noise when they want too. I do not think I have ever heard of a 3.4 that is quiet on start up, either valvetrain noise or piston slap is common. I would not worry too much right now. If you really want to find out what is going on, do a UOA when the weather warms up a little and you get some more miles on the oil. These engines are rather easy on oil (provided the LIM gaskets are not leaking on the 3.4) and a good syn oil like PP should easily go 7K miles or more. So basically if the oil does not seem right after 3k, then something else is going on and should be investigated.

 

[Hardware_Monk]

Thanks for the input wolfc70, and sorry for the delay getting back online. Windows 7 and XP were battling over the boot sector on the computer.

I agree about PP being long-lived. At about 3500 miles, it seemed a touch thinner, but it still had a base slickness between the fingers that hadn't gone away.

It also seems to have a good dirt-holding capacity. It wiped clean off the fingers and dipstick, but the when we dropped the oil out, it was plenty opaque with suspended particulates.

It could have gone longer, like you said, but with more warming weather I was getting a little piston slap around 2300 rpm under acceleration.

I moved it back to Edge 5w30, because the Castrol(s) seemed to make it quieter, when the weather was warm enough for them. True to form, the piston slap under acceleration went away, but I did pick up some noise at idle.

I decided I would have to pick which noise to worry about, or I'd be changing oil types or weights every 10-15 degree change. I had decided before the change that the idle noise was less important.

So, its Edge for now in the 3.5, but I know I'll be back to Pennzoil Platinum again for the next cold season, if I don't have reason to switch back beforehand.

I do want to do a UOA , because I suspect there's an issue with an injector, and I want to check for fuel dilution before it becomes a real problem.

The short-term oil in the Venture was another matter. It remained reasonably thick, by feel, but the base slickness was definitely going away; exactly opposite of how the PP behaved. A counter man at Carquest said that their store brand oil that I had used temporarily was made by Valvoline.

With the generally good warm weather results of Edge 5w30 in the Maxx 3.5, I also put it in the Venture 3.4. We'll see how it seems in a couple thousand miles.