Why did GM go to recommended 10W-30 on the 3800? My same year 5.7 recommends 5w? I don't get it.
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12-25-2010
Why did GM go to recommended 10W-30 on the 3800? My same year 5.7 recommends 5w? I don't get it.
12-25-2010
Two different engines first off.
My 3800 says use 5w-30 on the oil cap, but I use 0w-30
Its just the standard recommendations.
12-25-2010
You will be fine with 5w-30
12-25-2010
I run 5w30 in mine. Have for 5 years. no issues...Knock on wood
http://www.streetfire.net/video/2001...ynp_208097.htm
12-26-2010
So noone really knows why. I wasn't worried about it, always have used 5w, use it in all 15 of our semi's as well, for hundreds of thousands of miles.
I realize the 5.7 and 3.8 are different engines, just comparing different recommendations with liter size. The series III's did start putting those labled caps on, wasn't sure if it was a screw up, being lazy from a carry over of the old style 3.8, or someone leaving there pissmark in GM world.
I wouldn't see any reason's why anyone would have problems using it, I don't see a press drop between the two weights to cause concern-just seeing if anyone caught GM's reasoning.
12-26-2010
its the same reason every auto parts you go they always recommend dex 6 tranny fluid for all gms. you can use it but check the dipstick and itll tell you. i suppose maybe they figured a thicker oil might solve a few issues...idk. ive also been told on the new ls4 gp you have to run 5w 20 because if you dont it can damage the DOD system.
12-26-2010
Most new engine call for a 5w-20 or 0-20 to help free up a couples tenths of the mileage. Also the newer engines are built with a lot tighter tolerances.
12-26-2010
My 03 GT manual says 10w-30 is best for your engine, but 5w-30 is ok if it will be below 0* F before your next oil change.
Seems to use a little more oil when I switch to 5w-30 for MN winters, and has 122,000 miles currently.
12-26-2010
I bet it uses more oil in the winter because it runs longer between oil changes. Idle time.
12-26-2010
Honestly, in my experience cruising around the inter-web questions like this are rarely answered definitively. I believe a lot of the logic and technology is masked for a bunch of reasons, one being a little information is usually dangerous. For example, why did the coolant temperature gauges lose the numbers? It was because people freaked that their new vehicles’ were running so hot.
Anyway my best guess it that the recommend oil viscosity difference is nothing more than a timing issue. The Gen3 5.7L came out in 97, and GM was probably concerned about lowering their “overall corporate fuel economy” a notch so they spec’d for 5W-30. And the Gen3 3.8L came out in 04, so by then it was a proven and logic choice. Throw into the mix the 3.8L was a test bed for the GF-4 motor oil standard starting in 01.
GM seems to be always pushing the oil standards forward, the new dexos1 standard is now slowly becoming an industry standard. It would be very cool if an (GM) engineer would come on this site now and then like on other sites like BITOG.
12-26-2010
Excellent point!! When it gets below 0*F, it runs for at least 10min 2x a day going to and from work.Originally Posted by 01GTP
12-26-2010
the L67 likes thicker oil to keep oil pressures up and to keep everything lubed. i always ran 10w-40 in mine because even 10w-30 wasn't enough for me.
12-26-2010
The l31 Vortec had a factory installed engine oil cooler, the l67 does not, could possible reason for the one notch viscosity difference, I wondered the same thing as I have both vehicals (2000 Blazer with 4.3), and the 2000 GTP.
12-27-2010
The viscosity is the last numbers as most of us know. 0w-30 is no diff than 10w-30 except the W equals winter and the #'s before that is for cold flow. so basically on startup till normal op temp is reached, then the only thing that makes a difference during normal temp is the last set of numbers which is the visc. Mechanics tried to snow me on the they did it because of higher engine temps and normal fan start around 220-230 degrees. I'm just a stupid Mechanical Engineer for GE but that was bat**** crazy because they would use a 40 weight or 50 weight like my bike and the first numbers mean zip when hot. I'll tell you this-the same as why I couldn't answer reasons why GE or Siemens do certain things, I know GM engineers can't either.
12-27-2010
Please try to pay attention to where you're posting.
The reason they switched to 5w30 is partially due to the fact that they changed the spring and valve for the oil pressure bypass valve.
12-28-2010
Manufacturers used to use trick oil for the official MPG and HP tests. They would run lighter oil in both cases to free up a little HP and reduce the gas consumption.
Now, the federal government mandates that whatever oil the MFG uses in its testing must also be the official recommendation in the manual/oil plug. As such, they can no longer build an engine for 10W30 and test it using 5W30.
That, combined with newer materials and tighter tolerances mean that pretty much all newer cars will require 5W30 as opposed to 10W30 as they used to.
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