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#1474406 - 05/23/09 10:34 AM
Mobil One 15w50 or rotellaT 5w40
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Registered: 07/23/07
Posts: 57
Loc: ny
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I have an old Ford 5.8l Winsdor that presently uses Mobil 1 15w50 for oil pressure reasons. Thinking of switching to Rotella T 5w40 for the cold weather starts. Would I see a significant diff. in cold starts between the two at around 5 or 10 degrees f? What about the oil pressure when hot? Thanks
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#1474407 - 05/23/09 10:36 AM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: liberty]
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Registered: 08/21/08
Posts: 14329
Loc: Niagara Falls, ON, CA (near)
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You would see much better cold flow from the 5w40 versus the 15w50, and only a slight decrease in pressure when hot. IMO. Plus the 5w40 is a darn good oil! 
_________________________
'06 Hyundai Sante Fe - 330K KM's Current Oil: RLI 0w30 (Ask me why) Don't be part of the Sheeple, check frequently for wool over your eyes.
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#1474410 - 05/23/09 10:40 AM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: liberty]
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Registered: 07/03/05
Posts: 9030
Loc: NY
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Unfortunately there is only one way to really tell, and the reason I say that is because you mentioned oil pressure reasons. The 5W40 is going to be better for cold starts, and perform like a 40wt oil when hot, in an engine without OP issues there really won't be a whole lot of difference. In an engine with OP issues, the difference can be more noticeable.
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GOD Bless our Troops!
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#1474482 - 05/23/09 12:09 PM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: demarpaint]
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Registered: 07/15/05
Posts: 1504
Loc: On the deep blue.
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Do you have a real oil pressure monitor or a dummy gage?
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Signature? Why?
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#1474578 - 05/23/09 02:53 PM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: dave1251]
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Registered: 07/23/07
Posts: 57
Loc: ny
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A real guage. When hot i get 10 lbs at idle and around 25 lbs at 2000 rpm. The max pressure I can get is around 38 lbs no matter how high the rpm. This is with the 15w50.
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#1474582 - 05/23/09 02:58 PM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: liberty]
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Registered: 05/07/05
Posts: 270
Loc: Hawaii
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Consider another option: Castrol Syntec 5W-50.
_________________________
Now, whut we've got heah is failya to c'mmun'cate.
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#1474585 - 05/23/09 03:03 PM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: marco246]
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Registered: 07/23/07
Posts: 57
Loc: ny
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I heard that it shears very quickly. Is that true?
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#1474806 - 05/23/09 07:32 PM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: peterdes]
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Registered: 01/03/09
Posts: 4464
Loc: Illinois
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FrankN can tell more about this , but doesn't the M1 15-50 flow at a pretty low temp, like -40 or so? Better than some 5-30 dino oils at that temp. Just looked it up. -45 F. http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_10W-30.asp
Edited by tig1 (05/23/09 07:33 PM)
_________________________
2007 Ford Fusion 59,000 miles M1 5-20EP 2007 Ford Focus 70,000 miles M1 5-20EP 10,000 mile OCI M1 ATF
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#1474809 - 05/23/09 07:33 PM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: tig1]
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Registered: 08/21/08
Posts: 14329
Loc: Niagara Falls, ON, CA (near)
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Whats the pressure like with a standard 5w30? Just curious how bad the pressure problem is and how this thick oil is helping.
_________________________
'06 Hyundai Sante Fe - 330K KM's Current Oil: RLI 0w30 (Ask me why) Don't be part of the Sheeple, check frequently for wool over your eyes.
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#1475147 - 05/24/09 08:17 AM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: StevieC]
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Registered: 07/23/07
Posts: 57
Loc: ny
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I get about 2 or 3psi at idle and maybe a max of 20 psi.
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#1475152 - 05/24/09 08:24 AM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: liberty]
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Registered: 09/23/06
Posts: 7143
Loc: Bad Axe, MI
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Sounds like shes needs a new pump, them old v8 fords where like that. new pump and shed be be right back to norm press with a 5w30.
_________________________
"Always"..Mobil 1
Current fill 0w30 Green Cap
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#1475200 - 05/24/09 09:27 AM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: daman]
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Registered: 07/23/07
Posts: 57
Loc: ny
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I was told the exact opposite by an old time machine shop. He said bad main bearings are the culprit and suggested the heavier oil. I then called an oil pump manf. and they said a pump would not help either. The truck is a 1990 with 81K ORIGINAL MILES.
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#1475215 - 05/24/09 09:52 AM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: liberty]
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Registered: 09/23/06
Posts: 7143
Loc: Bad Axe, MI
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I've over the years worked around many of them older fords '84-'90 302's and 351's were all the same like that mileage didn't matter and yes new/tight cam bearings is where there pressure lies but a new pump is easer and more cost effective for old stuff like that,get your self a high volume pump and she'll be like new,trust me.....have been around it being done it does help/cure.
_________________________
"Always"..Mobil 1
Current fill 0w30 Green Cap
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#1475235 - 05/24/09 10:10 AM
Re: Mobil One 15w50 or rotellaT 5w40
[Re: daman]
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Registered: 07/23/07
Posts: 57
Loc: ny
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Do you reccommend a brand of pump
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