Oil weight debate

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clutchdust

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I got into a little debate with a local club member about oil weights. In conversation I told him I don't run the recommended 5w-30 in the c5, but 10w-30 instead. He turned his nose up at that and said he only runs what GM recommends. His argument is that their engineers have tested the engines and have to warranty them so them must know what they're doing. Good point, but my argument is they sell the same Corvette in Minot, North Dakota that they sell in Tempe, Arizona. Here in the southwest, where summer temperatures are almost always over 100* and winter temperatures rarely drop below freezing, I just feel a 10w is plenty thin enough. If I lived in Maine or Alaska or Wisconsin, I probably would run a 5w.
Just did an oil change an hour ago and even with the heavier 10w oil, my oil pressure at idle is only about 36psi. I certainly don't see a problem and it just makes me more comfortable. While I respect his reliance on the educated people who put these cars together, I think he is leaving out a relevant factor in his decision.
Thoughts?
 
Here in Florida the most common oil is 5W and 10W although our engines don't really see a lot of cold starts - winter in Michigan that's when you really "need" a thin oil ... But I dont think theres a problem with running 5W all year
 
Here's a good website:

http://www.bobistheoilguy.com/motor-oil-101/

Be sure and read all of the chapters. The guy who wrote it (A.E. Hass) is a physician and surgeon but has been studying motor oil and racing since he was in high school. I've not come across any credible sources that really disagree with his approach.

He believes the first number in the grade is only relevant at ambient temperatures and should be as low as possible to minimize start up wear.

DC
 
Now thinking about this, a few years ago (maybe 20) back in Germany 15w40 was the most common oil, 10w was considered the lightweight winter oil :lol:
 
Well based on reading that, I am completely wrong. But then again, even the factory information for the c5 and earlier cars is outdated by now.
The guy seems to know his shit. I did read the whole thing, well, most of it. I started skipping around when he was recommending different oils for Ferraris and Lambos. Figured if I ever get to that point, I'll learn it then.
 
I don't think you're THAT wrong with using the 10w oil in a warm climate, over the years I have used 10w30, 10w40,5w30 and 5w40 here in FL in LS1 and LS2 engines, many thousand miles (over 100k on my Z28) - never had an issue ..... Then again, coldest temp here is maybe 35F two days a year ....
 
I guess I'm really old school. I use a straight 30W oil. The bearings have the clearances within GM specs. .002-.003.
I've always thought the multi grade thing was a sales gimmick. Simple physics tells me that hot is thinner than cold. It's the additives in the oil that make it act like it's heavier than it is.
I even run straight 30 in the Model T- and with poured babbit bearings, I KNOW it's loose as a goose.
 
I suspect the best prevention to start up wear - just might be a "pre-oiler." At least I hope so!
Power on - solenoid opens - pressure to 50 psi, simultaneously flip fuel pump on - carbs fill - IGNITION (starter) - VAROOM!​

I can hardly wait!

Cheers - Jim
 
Funny this shows up.

I have an oil pressure drop at speeds over 5000 rpm. I tried out 5W30 synthetic and although the oil pressure was not going up at that speed, the drop was only 5 psi anymore where it previously was 15-20 psi and it stayed constant after the drop.

I'm inclined the believe I was experiencing oil pump cavitation.
 
After the 1st time I read that article, I happened to sit next to a lubrication engineer on a flight. I picked his brain about it and he agreed with the author's conclusions. He said modern oils are getting better all the time and a good multi-viscosity oil should always be chosen over a straight weight. Based on the article and my conversation with the lubrication engineer, I've switched my Suburban to 0W-30 and will be switching my Mom's car to a 0W oil as well.

Now, if I could just get my head around the ZDDP debate and figure out what to run in the flat tappet engine in my '73, I'd be all set. I like 540Rat's film strength analysis and David Vizard chimed in on that side as well but there are too many instances of cam failures for me to believe there is not some perfect level of ZDDP required.

DC
 
I think the real take-away from the article is that the most effective way to ensure minimal wear on start up is a crankcase heater. But it's unlikely few, if any, of us will actually do that.
Despite what I've learned from the article and a better understanding of what's going on, it doesn't change the facts that the vast majority of engines now-a-days easily run 100,000+ miles with no major engine failures. In fact, it seems my experience is that most high mileage engines are worn out at the top of the cylinder bores more than anywhere else, even the rotating assembly. Not sure how much oil weight really has to do with that wear.
 
Just happened to be in Walmart earlier today and checked out their oil selection. The Mobile 1 0W-30 actually says on the bottle "warranty protection for 5W-30 and 10W-30 requirements". Thought that was interesting.

DC
 
Belgian1979vette said:
Funny this shows up.

I have an oil pressure drop at speeds over 5000 rpm. I tried out 5W30 synthetic and although the oil pressure was not going up at that speed, the drop was only 5 psi anymore where it previously was 15-20 psi and it stayed constant after the drop.

I'm inclined the believe I was experiencing oil pump cavitation.
Click to expand...

Pressure is not volume. I know many of the old Ford FE motors do the same with little trouble.

Ralphy
 
clutchdust said:
Belgian1979vette said:
If concerned with startup run an accusump.
Click to expand...

According to the paper, an accusump won't be much help.
Click to expand...

I don't see a paper, but nonetheless.

The problem with a cold startup that you oil is more viscous (less fluid) and therefor there is more difficulty for the pump to pump the thicker oil into the bearings. The second problem is that as soon as you stop your engine after a drive, the oil will drain out of the oil channels, leaving air in place. If you start up an engine like that, the oil will first have to drive out the air, which can only go to the bearings or the lifters and then it can start lubricating the engine. At that point the engine is already turning. This can (!) induce metal to metal contact in those very first seconds untill oil replaces the air in the bearings.

This is exactly where an accusump helps you. It has stored pressurized oil, that pushes out the air in the channels and replaces it with oil, so you oil pump is immediatly starting to push against a fluid and builds up pressure.

What I see on my system is that as soon as I turn the key I have 40 psi pressure in the system even though the engine doesn't turn. It takes more than 30 seconds before the pressure drops to zero. I then will have long started the engine.
If I start the engine with a prelube of 40 psi, the pressure goes from there immediatly to the preset 75 psi.

It's the same reason why the prime an engine before initial startup.

Your choice.

BTW : if your engine only has 35 psi with a cold startup, either your bypass spring is too weak or your engine is worn. Not matter if you run 10w, 5W oil.
 
Last edited:
Ralphy said:
Belgian1979vette said:
Funny this shows up.

I have an oil pressure drop at speeds over 5000 rpm. I tried out 5W30 synthetic and although the oil pressure was not going up at that speed, the drop was only 5 psi anymore where it previously was 15-20 psi and it stayed constant after the drop.

I'm inclined the believe I was experiencing oil pump cavitation.
Click to expand...

Pressure is not volume. I know many of the old Ford FE motors do the same with little trouble.

Ralphy
Click to expand...

Correct, but you need both.
 
Belgian1979vette said:
clutchdust said:
Belgian1979vette said:
If concerned with startup run an accusump.
Click to expand...

According to the paper, an accusump won't be much help.
Click to expand...

I don't see a paper, but nonetheless.

The problem with a cold startup that you oil is more viscous (less fluid) and therefor there is more difficulty for the pump to pump the thicker oil into the bearings. The second problem is that as soon as you stop your engine after a drive, the oil will drain out of the oil channels, leaving air in place. If you start up an engine like that, the oil will first have to drive out the air, which can only go to the bearings or the lifters and then it can start lubricating the engine. At that point the engine is already turning. This can (!) induce metal to metal contact in those very first seconds untill oil replaces the air in the bearings.

This is exactly where an accusump helps you. It has stored pressurized oil, that pushes out the air in the channels and replaces it with oil, so you oil pump is immediatly starting to push against a fluid and builds up pressure.

What I see on my system is that as soon as I turn the key I have 40 psi pressure in the system even though the engine doesn't turn. It takes more than 30 seconds before the pressure drops to zero. I then will have long started the engine.
If I start the engine with a prelube of 40 psi, the pressure goes from there immediatly to the preset 75 psi.

It's the same reason why the prime an engine before initial startup.

Your choice.

BTW : if your engine only has 35 psi with a cold startup, either your bypass spring is too weak or your engine is worn. Not matter if you run 10w, 5W oil.
Click to expand...

I'm not following what you mean with the preset 75 psi.
 
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