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#2391592 - 09/29/11 05:23 PM Mobil 1 301 vs 303 GMC 6.5
onacorner Offline


Registered: 09/29/11
Posts: 2
Loc: MS
Hi Folks, Long time lurker need some advice pls. By accident I put a M1-301 filter instead of the M1-303 filter on my 98 GMC 6.5 diesel. The only difference is that the 301 has a 30 PSI internal bypass valve. All I noticed is a higher steadier OPR on my factory OP guage.

Is this filter ok to keep on the truck? Thanks Guys

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#2391596 - 09/29/11 05:27 PM Re: Mobil 1 301 vs 303 GMC 6.5 [Re: onacorner]
d00df00d Offline


Registered: 10/20/05
Posts: 10594
Loc: PA
welcome to BITOG!

30 PSI on the 301; what is it on the 303?
_________________________
2011 Mazda RX-8 R3
Castrol GTX 5w-20

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#2391609 - 09/29/11 05:48 PM Re: Mobil 1 301 vs 303 GMC 6.5 [Re: d00df00d]
daman Offline


Registered: 09/23/06
Posts: 11084
Loc: Bad Axe, MI
The 303(stock filter?) should have no bp valve as the bp is in the block on GM engines.

running that 301 would be fine as the block BP would open first if the 30 psi is higher,no sweat run er!!...
_________________________
"Always"....Mobil 1

Current fill: AFE 0w30

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#2391620 - 09/29/11 06:06 PM Re: Mobil 1 301 vs 303 GMC 6.5 [Re: daman]
cp3 Offline


Registered: 07/26/06
Posts: 2645
Loc: Kitchener, Ontario, Canada
That's what I thought but I guess it's different for the Duramax. Mobil doesn't list PSI just that they are both bypassed. Wix x-reference for the 303 says 15 psi and for the 301 8-11 psi.
_________________________
Dodge Charger|Pennzoil Platinum 5w20|Mopar MO-744
Pontiac G6 GT|Mobil 1 0w40|Mobil 1 M1-101

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#2391640 - 09/29/11 06:24 PM Re: Mobil 1 301 vs 303 GMC 6.5 [Re: onacorner]
cp3 Offline


Registered: 07/26/06
Posts: 2645
Loc: Kitchener, Ontario, Canada
Just cruised through the ACDelco online catalog and they list only PF1218 or PF35L for '98 diesels, neither of which have a bypass. Mobil's catalog says you should be using an M-302 which also has no bypass.
_________________________
Dodge Charger|Pennzoil Platinum 5w20|Mopar MO-744
Pontiac G6 GT|Mobil 1 0w40|Mobil 1 M1-101

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#2391651 - 09/29/11 06:41 PM Re: Mobil 1 301 vs 303 GMC 6.5 [Re: onacorner]
onacorner Offline


Registered: 09/29/11
Posts: 2
Loc: MS
Wow so no problems then...nice to know. Is there a spec advantage to use the 302 over the 303?

Do you think the oil preasure increase I am seeing is just due to using fresh RTS and MOS2 additive? It is a modest increase but it does show up on the factory guage.

Thanks for the welcome! I have learned so much from this forum over the years
_________________________
Adam in Gautier MS
USAF Retired Now Building Navy Ships

94 Ford, 97 Dodge, 98 GMC and 86 Mercedes Diesels and one gasoline buick park ave

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#2391660 - 09/29/11 06:48 PM Re: Mobil 1 301 vs 303 GMC 6.5 [Re: onacorner]
daman Offline


Registered: 09/23/06
Posts: 11084
Loc: Bad Axe, MI
The oil pressure increase could be just the new oil,i have a 1997 2500 6.5 and she blows some awesome OP,spec wise i hardly doubt there's a big or any difference in the two.

i have yet to find an over sized filter for this application(PF1218) i found one but it has no ADBV,witch IMO would be fine to use as these filters sit vertical.
_________________________
"Always"....Mobil 1

Current fill: AFE 0w30

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