Hi guys, i have a modified Jeep with a common GM 350 in it, freshly rebuilt, oil pressure was decent , about 40 PSI when cold and 7-10 PSI hot, it's being pretty warm in these days and i've seen gauge go down close to zero at idle, it is non accurate but i measured the pressure with a mechanical one previously so i know that was close to 10 PSI when hot, not sure about how many PSI is now but seems really low.
I'm running a Castrol Magnatec 5w40 plus a Comp Cams break in additive (i have flat tappets), i'm wondering if a Mobil 5w50 would be a better thing when warm compared to the 5w40 or is a waste of time and money.
I'm kinda afraid to use thick oil like 15w50 or even 20w50, i'm obsessed about get a dizzy/cam gear because too much load due to the thick oil...
I can get a 10w60 Bardahl here, what do you think?
Any help would be greatly apprecciated.
Mobil 1 5w50 viscosity
- Thread starter jeepers_creepers
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Hi,
jeepers_creepers - M1 5W-50 is an excellent product and has been part of the Porsche recommendations for a decade or more
It is used as a race oil by some
Welcome to BITOG!
I presume the Jeep is in Italy not BC?
The OP figures you've give are I presume on idle.
Normally for a GM V8 a light 5W-30 if all that's required to maintain more than adequate OP of over 50 psi at elevated rev's.
Even M1 0W-40 would normally be heavier than necessary.
Since you're running Magnetec 5W-40 now I'd check you're hot OP at high rev's and if it's well over 50 psi you don't need to run anything heavier. Also check you by-pass point, (maximum OP at high rev's when cold) to make sure you're below that point when the engine is hot at high rev's.
Since it's a flat tappet engine, another option is a 10W-30 HDEO.
Thank you for asnwering me guys, i went for the Mobil 1 5w50, oil pressure when warm seems to be sligtly higher than before, same pressure when cold.
Next fill try a dino or synthetic 20w50 motorcycle oil. Actually Brad Penn 20w50 might be a good choice.
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Originally Posted By: JethroBodine
Next fill try a dino or synthetic 20w50 motorcycle oil. Actually Brad Penn 20w50 might be a good choice.
Originally Posted By: CATERHAM
Originally Posted By: JethroBodine
Next fill try a dino or synthetic 20w50 motorcycle oil. Actually Brad Penn 20w50 might be a good choice.
Of course hot oil produces a much lower OP than cold oil but that's not the point.
Running 3 grades heavier than spec' oil, particularly a low VI 20W-50, you simply will not be able to use high rev's in a Chevy V8 without the oil pump going into by-pass mode.
Originally Posted By: Doug Hillary
Hi,
jeepers_creepers - M1 5W-50 is an excellent product and has been part of the Porsche recommendations for a decade or more
It is used as a race oil by some
Originally Posted By: CATERHAM
Of course hot oil produces a much lower OP than cold oil but that's not the point.
Running 3 grades heavier than spec' oil, particularly a low VI 20W-50, you simply will not be able to use high rev's in a Chevy V8 without the oil pump going into by-pass mode.
Hi,
Falcon_LS - Sorry I can't help with any info - I have no access to it
Originally Posted By: Doug Hillary
Hi,
Falcon_LS - Sorry I can't help with any info - I have no access to it
Hi,
Falcon_LS - We only have the "normal" M1 5W-50 here in OZ - Porsche Approved of course. It is quite a big seller here
I think flow is more important than pressure. Pressure is just easier to measure. The size of the engine oil passages are fixed by design, so by increasing viscosity to raise pressure, you decrease flow. Engine designers think about this kind of thing, and that is how recommendations for viscosity are made.
If you think your pressure is low, change the pump. However, a high output pump can get too much oil on top of the engine because the oil can't drain back to the sump as fast as it is being pumped to the top. Stick to OEM specs.
Originally Posted By: Georgiadave
I think flow is more important than pressure. Pressure is just easier to measure. The size of the engine oil passages are fixed by design, so by increasing viscosity to raise pressure, you decrease flow. Engine designers think about this kind of thing, and that is how recommendations for viscosity are made.
If you think your pressure is low, change the pump. However, a high output pump can get too much oil on top of the engine because the oil can't drain back to the sump as fast as it is being pumped to the top. Stick to OEM specs.
Originally Posted By: Shannow
If you look back, we calculated that the increase power requirement on the oil pump from higher viscosity was less than turning the headlights on...
Put a Melling oil pump in it. Problem solved.
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