xW-40 Oil Questions

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Jan 18, 2004
Shelby, NC
Mobil 1 0w-40 @40c = vis of 80 Mobil 1 5w-40 @40c = vis of 102 Rotella 5w-40 @40c - vis of 90 (all from the company websites) Now my question is this: Would the much thicker Mobil 1 5w-40 be that much better at protection for a high revving engine (3.5 Isuzu and 3.0 Nissan) than the thinner 0w-40? Or would the Rotella being right in the middle be a better choice for these overhead caammed engines?
I think the question is unanswerable. It really depends on a lot af variable factors. All three are 40 weights and are very good oils. I suspect that the M1 would be the better oil because the Rotella is a group III and the 0W40 thins out quite a bit because of shearing. But again I think that any of the three are perfectly good oils.
How fast would the 0w-40 shear? I plan on a 4k oci on both vehicles. The Delvac/SUV oil is not available here yet so that complicates matters somewhat. The Isuzu is known for clogging the PCV and EGR systems and also the oil control rings thereby causing consumption, just wondered if the Rotella's HDEO additives would help clean some of the junk up.
The 0W40 will work just great for you with 4 to 5K oil change intervals. Some people don't care for the 0W40 because it starts out as a low 40 weight and thins to a high 30 weight after a few thousand miles then thickens back up to a 40 weight. I believe the oil is built to do this so that it won't thicken out of grade during extended drain intervals. I have used it in the past and liked it. Check out the used oil analysis section and you'll find a lot of information on the M1 0W40.
With 4K miles OCI you can use a good dino oil like Castrol GTX 5w30 and your engine will last longer, based on lubrication, than you will want to drive it. But if you want to spend the extra $$$ which is fine I would use Mobil 1 10w30.
With the 4k intervals you plan I would use the Rotella T Syn. 4k is a very short time for any of these oils. Rotella T Syn will hold up plenty well for 4k miles and is the least costly of the bunch. If I were gunning for 10k or longer intervals I would use the Delvac/"SUV" 5W-40. John
Viscosity at 40C doesn't really matter in this case unless you drive 1 mile one way (in that case you'd better off with Xw-30). Viscosity at 100C for the oils you listed is about the same. Composition (base and additives) are very different for the 3 oil and performance should not be compared directly. 0W-40 is a very good oil, as well as Rotella. I can't make any conclusion about Mobil's 5W-40 since we haven't seen any real results yet. Additive package in 0W-40 seems a bit better than in Mobil 5W-40. But then again these oils are so different that can't be compared directly. For the longer drain Rotella might work better. I wouldn't worry much about the choice - 5/10W-30 will work the same for your engines plus you get some fuel savings. Both engines are very reliable and wear seems to be very low. Few mentioned that Isuzu might have some oil consumption issues in that case 5W-40 is better, but I assume that synthetic 10w-40 would work the best if you have serious oil usage. Regards,
Yeah the Trooper uses about 1 qt per 3k which Isuzu says is normal (heck they say 1qt per 1k is normal [Eek!] ). I think that the PCV system may have some junk in it, not stopped up mind you justy some junk and the HDEO may help clean that mess up. I have run 5w-30 and 10w-30 Mobil 1 in it and it used the same amount, but have since read that they are thinner than "regular" 30 wts. My Assumption is that a 40wt, even a Mobil 1 40wt (0w-40) may help the issue some. I also drive to Pittsburgh (through the WV mountains), and to Birmingham on a semi-regular basis so the added weight would help protect both engines just a bit more.
Yeah the Delvac/SUV oil looks to be the stoutest of the bunch and if available here is what I would use. With the driving style (short trips then high speed interstate) we do I would not be comfortable with more than a 5k change no matter what, especially with the proclivity of the Trooper to burn oil after the 2000 mile point in the change interval. The Rotella was my original thought especially with the LOW price at the ol' wallyworld these days and the cleaning properties of HDEO's.
The answer is NO because 40C is a stupid comparison point surpassed somewhere when your engine is simply 'warming up' and you should not really be 'revving' things major league anyway. That said, all will protect just as well...with the 5-40's having slighly more cojones than any 0W-x eg. 0-40.
Well, if you are talking about operating temperatures, one 40wt is as good as another. The difference in visc. between two oils at 40c will not be the same at 100c. See the thread "0W vs 5W" on this page. You will see that one oil had a difference of 8.5 at 40c and less than 2 at 100c. One thing for sure, you or your engine won't be able to tell the difference. [Big Grin] Dave [ May 10, 2004, 02:12 PM: Message edited by: DavoNF ]
Hey ncirish, If it were me, for 4k mi intervals I'd use either Delvac 1300 Super 15W-40 or Delo 400 15W-40 year-round. Both of these HDMOs should have plenty of life left at the 4k mi mark.
Well excuse me for being stupid there Dr T. Math is not my strong suit, I teach History. The viscosity at 40c looked like the proper number. But after doing teh math I found out it is not. Now as for the 5w vs 0w oils, I am going to use them in two Japanese engines that are relatively free-wheeling. I am used to Ford Ranger engines where 3000 is about all you rev to. Whereas in the Nissan I regulary go to 4000+ and the Isuzu goes above 3500 regulary. On the interstate they both kick down in cruise to those speeds from time to time. Now what I dont want to do is use an oil that is too thick, especially with the Isuzu and it's godforsaken ecm and valve train characteristics. Just want a little extra protection and oil weight is all.
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