Somebody's sig is tooooo wide.

 

Your premise here is wrong. The higher number, in this case the "30" is what keeps the oil thick enough to not flow out. That's the whole point of "multi-vicosity" oils. The best of both worlds within the parameters of the upper and lower numbers.

 

Holly crapola! I hope this is not true. I just did an oil change yesterday and was going to go with 10w 30 but opted for the 5w 30 since that has been what I have been using. Oh well next change I will go with the 10w 30

 

Regardless if one is theoretically better than the other, I can assure you there are millions of cars running around, including almost all C5's, with 5-30 that will run damn near forever with either.

We do tend to get a little **** on the forum about these things. GM would not recommend it for so long if it was going to be a problem (also, keep in mind the comment a few posts back about synthetics). I'm sticking with 5-30, even here in Houston because I feel very comfortable with it's ability to do it's job. And my car sits all week long, so getting the oil flowing as quickly as possible on start-up is the most important issue.

 

As usual here, Chicken Little Rules...

Just for once, can't you guys have faith in all the hundreds of scientists and engineers who designed this incredible sports car that you keep calling America's Icon. Just for once?

Who do you believe? Someone who misread that article or the petro-chemical engineers that worked on the synthetic oils? I know where my money is.

 

 

I'm not sure what you are saying here, both 5w-30 and 10w-30 are in the manual.

 

The manual actually says use the lowest viscosity oil recommended. Regardless of temp the 5W-30 is the recommend oil. (I think it is actually on the cap). 10W-30 is also acceptable, as long as temp stays above a given temp! Any oil higher in viscosity not recommended. The 20W-50 says it could cause engine damage.

Good oil flow at the design viscosity provides the exact design film thickness for the rotating assembly and bearing, and proper heat transfer.

The 5W gives better gas mileage and cold starting protection.

Mobile one list 5W-30 as the "NEW CAR Formula" and 10W-30 as the "High Mileage Formula". Higher mileage= more clearance=higher viscosity oil needed since you need a thicker film with the greater clearance a used engine has.

Remember that there are natural oils, blends, full synthetic. So depending which oil the article is refering to makes a big difference. My 1990 Chevy 350 PU had a recommended 5W-30 in the manual. Several months later I got a recall sheet to change the manual saying 10W-30 recommend because normal 5W-30 did not protect sufficently at start up, "UNLESS IT WAS SYNTHETIC". Since they were not recommending using synthetic oil, they recommended 10W-30. From fuel economy perspective the 5W-30 was better. They just were not recommending us red necks pay for synthetic oil prices back in 1990! Less spending money for beer and chips:)

"THIS DOES NOT MEAN 10W-30 WAS BETTER" Only better if not Synthetic!!

Chevy recommends 5W-30 synthetic for your Corvette! Todays high performance synthetic oils provide the necessary protection.

Notice Mercedes recommends the 0W-40 Mobile One. They have designed their engine to use it!

Of course, other than doing a dyno every thousand miles on two exact Corvettes with 5W versus 10W for a 100,000 miles under the exact same driving conditions, I don't know how you can determine the wear. You probably would never recognize a difference, other than in gas mileage and oil pressure.

For all those 10W and higher oil users on new Corvettes, what is your engine oil pressure running?
George

 

What about those of us using Amsoil 0W-30 Seires 2000? :confused: According to the webiste is superior to all others regardless of temperature extremes. Anybody care to comment? :cheers:

 

I'll probably blow the engine up before there's any substantial wear :lol:

 

I beg your most humble pardon dear Sir.. I do believe my premise is correct.

You don't start with 30 unless your engine has already warmed up to operating temp. If this is the case there is NO difference in viscosity between 5w30 and 10w30 oil.

Both 5w30 and 10w30 have the EXACT SAME VISCOSITY at higher temperatures.
At lower temps...(starting cold) 10w30 is twice the viscosity of 5w30.

From "AutoEduacation.Com":
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" Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. "

"Oil weight, or viscosity, refers to how thick or thin the oil Is. The temperature requirements set for oil by the Society of Automotive Engineers (SAE) is 0 degrees F (low) and 210 degrees F (high). Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating. Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. You will hear them referred to as multi-viscosity, all-season and all-weather oils. When choosing oil, always follow the manufacturer's recommendation. "

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As several members have pointed out, 5w30 is reccomended for colder climates and 10w30 for warmer areas of the country.
Here's my rule of "thumb":

Above the Mason Dixon Line, use 5w30.
Below Mason Dixon, use 10w30.
GM doesn't know where you might live with your Vettte so they reccomend both of them.

Best regards,

 

Okay, I'm not a Chemical Engineer, so I could be wrong. But I don't think my overall premise is out of line. Let me ask you for your opinion, as you seem to have read a lot on this subject. Which do you think is thinner: 5 weight at ambient temperature, or 30 weight at 210 degrees?

For the record, I don't know for a fact, but if I were a betting man, I'd bet the 30 weight at 210 is thinner. The reason I think this is based upon draining hot oil from my car many times. Just looks a whole lot thinner. If this is a correct assumption, then you are still not in harms way with 5 weight on start-up, are you?

Thanks for your opinions, and if I'm wrong, you have my apology.

 

OK, to try to clarify what several of the posted links have stated: An oil that has a rating of 5w-30 performs ( in terms of "thickness" or "thin-ness" ) as a 5 weight oil at 0 degrees F, and as a 30 weight oil at 210 degrees. So if the issue of viscosity index improvers is a non-issue with synthetic oils, and given an LS1 that still has in-spec clearances, then the weight oil of choice in a temperate climate zone would seem to be 5W-30. As the ambient and engine temps go up both 5W-30 and 10W-30 become more similar in terms of "thickness". So it is only how "thick" the oil is at cold temps (startup) that really is of concern to us. I think everyone agrees that a 5W-30 would be better when starting the engine during winter up North at -30 degrees. The question becomes whether 5W-30 is still a better choice for Florida in the summer. Remember that as the ambient and ( therefore ) engine temp goes up both weight oils become more similar in terms of "thickness". If a 5W-30 is fine for Canada in the summer where the ambient temp may be 90+ degrees, then why would it not be fine for Forida where the ambient temp may be 105 degrees? After all, at 100 degrees both weight oils are already becoming more similar in terms of thickness. Plus, I would bet that the difference between 90 degrees or 110 is noticed far more by us than by the oil or engine! :cheers: :D


[Modified by 1g1yy, 8:45 PM 11/5/2002]

 

(quote)Just for once, can't you guys have faith in all the hundreds of scientists and engineers who designed this incredible sports car that you keep calling America's Icon. Just for once? (quote)

Is the the same guy who designed the gas guage sensors, my seat that rocks, my battery that leaks acid on the computer, and my headlights that rub the hood when they open.... Oh, don't forget the locking wheel (haven't had that one happen yet (knock on wood).

Or it could have been the guy who designed the hatch to pour water in the car when it is opened? Or the guy who made water dump in when the door is opened?

Wait, maybe it was the guy who made it fast as he11 and look good to boot. In that case OK! I will believe him.

 

All I know is that I am a simple Commercial Real Estate Guy who Drag Races a 2000 C5 Coupe a few times each month. My C5 has about 23000 miles on it and has about 200 drag races. My oil policy is simple run 5W30 Mobile One change the OIL before each race outing and the filter about every 2000 miles. Filter out the pre-PCV oil, launch at about 1200 RPM and enjoy.

Does it work? about 3 weeks ago FLP installed the Vinci Hi-Performance CNC heads and roller cam setup and to my surprise THERE WAS NO VISIBLE WEAR ON THE CYLINDER WALLS!!! In fact the origional hash marks from the factory are still fully visible. I have no adverse oil consumption either.

Best times Route 66 1/8 mi. 7.56 sec., 92.3 MPH, 1.720 60' Great Air, at Byron Raceway 11.99, 114.0 MPH, 1.725 60', Good Air.

FOR WHAT IT'S WORTH

JR :yesnod: :yesnod: :yesnod: :yesnod: :yesnod: :yesnod: :yesnod:

 

the thinner the oil the faster it reaches the parts in the engine. years ago with the ZR-1 it had trouble with the cams seizing in the heads when started in cold weather becaused it took to long for the oil to get to the heads and they went to 5W-30 to help with this problem. all aluminum engines have very tight main bearings when cold because the clearance opens up as the aluminum expands so having a thinner oil is a benefit. with all aluminum race engines where they use thicker oil they use oil heaters before starting the engines. the C5 R do this. :chevy

 

Both 5w30 and 10w30 have the EXACT SAME VISCOSITY at higher temperatures.
At lower temps...(starting cold) 10w30 is twice the viscosity of 5w30

Having once worked for an oil company, I can remember that the viscosity test is done at different temps to establish the multi-viscosity rating. The 5 is for low temp, the 30 is for high temp. Better use what the manufacturer recommends.