5W30 vs 10W30, pre 2000 Northstar 84 degree weather - Page 2

JohnnyO · #16 (**permalink**) 03-02-06, 09:40 PM

Dittos what Chevelle said about the viscosity improvers back in the 70's-80's. I worked at an Olds/Cadillac dealer then and I remember in 1984 getting a letter from GM saying to stop using 10w-40 oil because the viscosity spread was too wide and the oil wasn't performing like it should. Today's oils would likely be fine, but back then they told us to use 10w-30. Stupid of your oil change place not to stock ANY 10w-30 though. I'd go somewhere else or do it yourself.

Patrick7997 · #17 (**permalink**) 03-03-06, 01:03 PM

They did that to me once....

I drove the car back the next day and demanded they change it back out. After brief & mild protestations, they drained it & refilled it with 10w30.

5w30 seems to be the "default" setting at those places now, though, so you have to specify....

I agree with Johnny O, unless I'm too busy or too lazy.... by the time I sit there in line for a half hour, I could have drove it up on my ramps and done it myself. Plus it saves a pile of money.

boricuacaddy · #18 (**permalink**) 03-03-06, 01:25 PM

The funny thing is, I take my Caddy to the dealer to have my oil change, and they always put the 5w30 in my car. I would think they should know what is recommended for my car. Next time I go back I will make sure to talk to the service rep. about using the correct oil in my car.

David

dkozloski · #19 (**permalink**) 03-03-06, 02:35 PM

Flat tappet cam followers were the last stumbling block to adopting 5W-30 oil as a fuel saving measure industrywide. The difference in milage is small but substantial enough that the car makers decided it was worth the trouble to improve CAFE milage. Flat tappets were the last high pressure sliding contact left in the engine design that called for the 10W spec under certain conditions.

**Ranger** · #20 (**permalink**) 03-03-06, 05:32 PM

The thing that baffles me is that 5W30 & 10W30 are both 30 weight after a very short warm up period. So where is the fuel milage savings? I'm sticking with 10W. I just feel better about it. Is the "old school" starting to show again?

Dadillac · #21 (**permalink**) 03-03-06, 07:12 PM

Quote:

Originally Posted by Ranger

The thing that baffles me is that 5W30 & 10W30 are both 30 weight after a very short warm up period. So where is the fuel milage savings? I'm sticking with 10W. I just feel better about it. Is the "old school" starting to show again?

We both have the same engine. On the coldest of days, like -5*, my car, with 5w30, will start a little easier and quicker than yours, using 10w30. All of this oil talk is ludicrous. It is amazing how much stock people put into "oh my God, what oil should I use". It amazes me. I stand by my statement above. With a few esceptions, 5w30 can be used in about every engine produced since about 1985. It really isn't that critical.

Don

**Ranger** · #22 (**permalink**) 03-03-06, 07:52 PM

I agree Don. Oil wars have been started over the question. Hell, have you ever checked out bobistheoilguy? A whole site dedicated to it. They have 5W30 running through their vains. They obsess about it.

dkozloski · #23 (**permalink**) 03-03-06, 08:50 PM

The way I heard it sonny, 5W-30 doesn't provide sufficient protection during the first few minutes during a cold start for a flat tappet cam. Once it's warmed up all is fine. 60 years ago we used straight 5W in the winter and got away with it for a while. At the mid temp range where the oil normally operates 5W-30 is still slightly thinner than 10W-30. I admit it sounds like stomping on pissants while elephants are running up and down the halls. This is what the engineers claim and I'm just passing it on.

Zorb750 · #24 (**permalink**) 04-08-06, 02:46 PM

I'm partial to 5w40 PAO (Mobil1) synthetic (not that Castrol Syntec Swill) myself. It's spec for most better Euro cars for a reason you know.

Your initial circulation is quick and it doesn't thin as much as 10w30 at high temperatures. Play with it at higher RPMs, especially with the windows open. It sounds smoother, more harmonious. Seriously! Sometimes in the summer I used to run 15w50 Mobil1 on it when I took it to the track, but I would notice the smoothness benefit coming home so I started doing that during the summer all the time, until Mobil1 came out with the 5w40, now I am very happy with it. For you "old school" guys, 15w50 mobil1 has a lower pour point than 10w30 dino juice anyway, not that I was running it in the cold.

That's my vote.

mtflight · #25 (**permalink**) 04-09-06, 01:15 AM

Quote:

Originally Posted by Zorb750

I'm partial to 5w40 PAO (Mobil1) synthetic (not that Castrol Syntec Swill) myself. It's spec for most better Euro cars for a reason you know.
... Play with it at higher RPMs, especially with the windows open. It sounds smoother, more harmonious. Seriously!

Sounds like the placebo effect.

Zorb750 · #26 (**permalink**) 04-09-06, 02:38 PM

Try it and see. Any time you drive the oil pressure up, you also smooth out any internal vibration related issue, no matter how slight.

Also, try reving it, letting it come back down, then taking it up to 3000 RPM next to a brick wall. Tim Horton's drive throughs late at night work very well, after you get your coffee just in case you piss someone off. The brick wall makes every little noise more evident, especially the high pitched ones.

I mean it. I'll bet you a case of 5w40 oil.

Zorb750 · #27 (**permalink**) 04-09-06, 02:42 PM

On the point of oil thinning, it's true in the case of conventional oils that 5w30 may thin a bit more at high temperatures.