Mobil One 15w50 or rotellaT 5w40

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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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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! \:\!
 
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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.
 

liberty

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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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Whats the pressure like with a standard 5w30? Just curious how bad the pressure problem is and how this thick oil is helping.
 
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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.
 

liberty

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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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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.
 

OVERKILL

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 Originally Posted By: daman
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.
High volume pumps on a Windsor are band-aide. If it has low pressure, the rod and main bearings are likely worn. The stock pumps are good, and the only REAL reason to run an HV pump on a stock bottom-end is if you are feeding a blower and need the extra oil volume. To the OP: How long have you had the gauge on the truck for? Mechanical or electric?
 

OVERKILL

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Another issue with HV pumps in a Windsor is the hex-shaft that runs the pump from the distributor. Heavy oil and an HV pump has been known to twist and sometimes break the hex-shaft. I've got a little HV oil pump story: A good friend of mine had a very high mileage (~400,000Km) 302 in his Mustang. The engine had an unknown history and had seen a lot of passes on Nitrous, as well as numerous nitrous back-fires. The engine didn't have very good oil pressure; 12lbs IIRC with the stock pump in it at idle with 20w50 in the pan. So, he swapped in a Melling HV pump. His oil pressure got better (around 20lbs) with the same weight of oil and he continued to use the car. One day at the track, I broke my tranny, and he had a Nitrous "issue" which involved a mouse eating his injector harness, causing an intermittent injector, and subsequently a melted plug and burnt valve. He was running stock heads, and I had mine sitting around, and so instead of fixing his head, we just swapped it out with one of mine. The head from my engine was MUCH cleaner than his and he made a remark about this after we put it back together. Even though it ran fine, from the pressure issue the engine had, we knew the bottom-end wasn't overly healthy. That fall, we pulled the engine out of his car and tore into it. ALL the rod bearings showed copper. A LOT of it. As did all the main bearings. Yet with the HV pump, it had around 15-20psi hot at idle even after the most recent incident. So yeah, the HV pump made what he saw on the gauge look better. But it didn't change the fact that the bottom-end of that engine was very worn and needed attention.
 
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 Originally Posted By: OVERK1LL
 Originally Posted By: daman
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.
High volume pumps on a Windsor are band-aide. If it has low pressure, the rod and main bearings are likely worn. The stock pumps are good, and the only REAL reason to run an HV pump on a stock bottom-end is if you are feeding a blower and need the extra oil volume. To the OP: How long have you had the gauge on the truck for? Mechanical or electric?
well yea it's a band-aid but it works for an older truck,how much $$ would one want to stick in the thing? been there done that, it works and works fine doing a new pump intstall.
 

OVERKILL

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 Originally Posted By: daman
 Originally Posted By: OVERK1LL
 Originally Posted By: daman
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.
High volume pumps on a Windsor are band-aide. If it has low pressure, the rod and main bearings are likely worn. The stock pumps are good, and the only REAL reason to run an HV pump on a stock bottom-end is if you are feeding a blower and need the extra oil volume. To the OP: How long have you had the gauge on the truck for? Mechanical or electric?
well yea it's a band-aid but it works for an older truck,how much $$ would one want to stick in the thing? been there done that, it works and works fine doing a new pump intstall.
I think you and I have different views on what the definition of "works" is. Will the HV pump make the oil pressure gauge read higher? Yep. Will the HV pump fix the worn bottom-end of that engine? Not a chance. So whilst it "works" in the sense that his gauge will read higher, the bottom-end of that Windsor is still FUBAR, and it still needs bearings.
 
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