[quote author=yooper link=board=2;threadid=3749;start=0#msg27784 date=1058575689]
Syth is just plain better. I got a HUGE cleaning effect when I switched to Mobil 1 at 133K. 2500 miles or so later the oil was BLACK. I use 15W-50 year round up here in the far North and the truck turns over EASIER in the winter than it did with 10W-30 dino oil. Synthetic oil flows much better in the cold than dino oil and the weight ratings are not equivalent for simple viscosity at temperature. I think this is the third time I've posted this this week. Make sure you read the synthetic oil thread and the sludge thread.
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Yooper,
I'm sorry but you are simply not correct about the weight ratings being different for synthetics than mineral oils. Synthetics tend to be more temperature stable, but 15w-50 is the same weight if it is mineral or synthetic.
The 15w part means that the oil must be less than a certain CST at a certain temperature, in the case of 15w it must be less than 6500 cst @ -20C I believe, for 10w it must be less than 6500 cst @ -25C (I know the temps for sure just not the cst breakpoint). I will again as I offered earlier this week be happy to provide the mobil pdf charts that show the viscosity of their oils at all tempurature and you can compare the mineral and synthetics.
I'm not trying to be jerk, but I don't like seeing inaccurate information posted. There is enought bad info out there already. Please see the below post I made to bob is the oil guy concerning mineral v. synthetic oil properties. Please note that you can not compare the 20w-50 to the 15w-50 because they are not the same weight. You have to compare the 10w-30 formulas because they are the same weight, and you will see there is a difference in cold flow properties but it is not great.
I just wanted to post some random notes concerning oil viscosity. Mark from NY was kind enought to send me the oil PDF's from Mobil, from which I took Mobil 1 graphs and overlayed a couple of the Mobil clean drive oils (Synthetic v. Mineral). It is interesting when you look at the graphs (Vertical Axis Centistokes in a logrithmic scale, horizontal tempurature also logrithmic) because they are linear. Here is where it gets real intersting:
1) The mineral 10w-30 runs close in thickness to the M1 10w-30. This is much different than the 20w-50 mineral v. 15w-50 M1 where the M1 15w-50 is far superior in pumpability at low tempuratures (noting of course that these oils are two different weights).
2) The M1 0w-30 and 5w-30 are so close through their tempurature spectrum that their lines run together. They are pratically the same oil.
3) M1 0w-40 has a flatter slope than any of the other oils, meaning that it changes thickness the least.
4) To give a few ideas about the thickness as various points:
For the oils to be 10,000 cst in thickness the tempurature of the oils is as follows:
M1 0W-30 & 5W-30 -33F
M1 0W-40 -30F
M1 10w-30 -26F
Mobil Mineral 10w-30 -18F
M1 15w-50 -15F
Mobil Mineral 20w-50 7F
For the oils to be 3000 cst in thickness the tempurature of the oils is as follows:
M1 0W-30 & 5W-30 -12F
M1 10w-30 & 0w-40 -7F
Mobil Mineral 10w-30 0F
M1 15w-50 8F
Mobil Mineral 20w-50 24F
For the oils to be 500 cst in thickness the tempurature of the oils is as follows:
M1 0W-30 & 5W-30 27F
M1 0W-40 40F
M1 10w-30 32F
Mobil Mineral 10w-30 38F
M1 15w-50 54F
Mobil Mineral 20w-50 67F
And finally for the oils to be 15 cst in thickness the tempurature of the oils is as follows:
M1 0W-30 & 5W-30 175F
M1 0W-40 207F
M1 10w-30 182F
Mobil Mineral 10w-30 183F
M1 15w-50 230F
Mobil Mineral 20w-50 228F
Take what you will from these numbers, but my view is 1) if you live in cold climate use the M1 0w-30, 5w-30, or 0w-40, 2)Synthetic 15w-50 offers no cold start advantage over mineral 10w-30, but does offer a significant benefit over mineral 20w-50, 3) As you get to operating tempurature (212F) all the 30 weights are the same, the 40 weight is thicker and the the 50 still thicker. Obviously in an extreme situation the Synthetics will withstand higher temperatures than the mineral oils before breaking down.
For me, I am now using Mobil 0w-40 in all my cars, a 94 BMW 525i, a 91 nissan Pathfinder, and a 96 Toyota landcruiser. I like the idea of the better oil flow at lower tempuratures, but still feel the 30 weight is to thin on the high end.
Interestingly, my Landcruiser and Pathfinder both call for 10w-30 in warm weather, but overseas they spec 20w-50 for warm weather. The 40 weight gives me a better feeling.
Thanks for the replies. I have been running 10w-30 dino, pressure is normal ( 3/4 at speed and right above the 1/4 at warm idle). Actually I am exactly half - way between Tampa and Orlando, we actually do get some low 30's and high twenties in the "winter" but not sustained. I look for M1 0w-40, if not I'll get 10w-30. Thanks again.
Wow. Thanks! I'm not sure how to explain my experience this winter, though. It was a clear difference - it was about -10 F every morning for a couple weeks. In the middle of this period I changed from what I thought was mineral 10w-30 over to Mobil 1 15w-50 and the engine turned over much quicker on cold starts the very next day and thereafter, and was never sluggish for the rest of the winter, including in temps to -25 F or so. I parked it outside every night. :-\ ???
