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Castrol / Mobil 1 blend? #5441652 05/29/20 09:40 AM
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mbres2000 Offline OP
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I have 4 qts of Castrol GTX synthetic blend and 1 qt of Mobil 1 left over from previous oil changes. Both are 10W-30. Any problem mixing those together in an old Chevy 350 in which I've been running a variety of oils and weights from 5W-30 to 10W-40, both conventional and synthetic?

Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441662 05/29/20 09:47 AM
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kschachn Offline
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There are likely hundreds of threads on mixing oils here on Bitog. Perhaps read some of those?


1994 BMW 530i, 253K
1996 Honda Accord, 289K
1999 Toyota Sienna, 437K
2000 Toyota ECHO, 290K
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441671 05/29/20 10:00 AM
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JeffKeryk Offline
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Sounds nasty... Go for it!


2018 Tesla Model 3, Medium Range Battery
2018 Lexus RX450h
2013 Lexus GS350 F Sport
2006 Acura TSX
2001 Tundra Access Cab, 1998 Accord LX, 1968 Corvette L36 Roadster, 1965 Olds 4-4-2
Re: Castrol / Mobil 1 blend? [Re: kschachn] #5441674 05/29/20 10:01 AM
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mbres2000 Offline OP
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Thanks. This thread answered my question and then some!

https://www.bobistheoilguy.com/foru...rue/mixing-oil-weight-brands#Post5157037

Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441689 05/29/20 10:12 AM
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ka9mnx Offline
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Every time you change your oil and change brands you are "mixing" oils. More so if you don't change or drain the oil filter.


2005 Ranger 3.0 - SuperTech Syn 0w-20/Motorcraft
2000 4Runner 3.4 - SuperTech Syn 5w-30/Toyota
1997 B2500 Van 3.9 - M1 HM 10w-30/Mopar
1993 F150 4.9 - SuperTech Syn 5w-30/Motorcraft
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441693 05/29/20 10:18 AM
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nomas Offline
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Some people here would die if they knew what I mixed over the years . No issues ever .

Re: Castrol / Mobil 1 blend? [Re: nomas] #5441694 05/29/20 10:20 AM
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kschachn Offline
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Originally Posted by nomas
Some people here would die if they knew what I mixed over the years . No issues ever .

Of course not. As is always the case with this oft-repeated question, if the oils are API licensed then both must pass ASTM D6922 and will be miscible. The mixture will not cause immediate harm.

But that isn't everything.


1994 BMW 530i, 253K
1996 Honda Accord, 289K
1999 Toyota Sienna, 437K
2000 Toyota ECHO, 290K
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441721 05/29/20 10:54 AM
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rob1715 Offline
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Mix them all day long as long as they're the same weight and are certified.


2003 Toyota Matrix - Whatever synthetic is cheapest - OEM Filter
2019 Kia Sorento - OEM Filter

“Think of how stupid the average person is, and realize half of them are stupider than that.”
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441729 05/29/20 10:59 AM
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GSCJR Offline
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No problem doing that; mix away.


07 3.5L VQ35DE NAPA FS 5w-20 ProSelect 21358 158KM
10 3.5L 2GR-FE NAPA FS 5w-20 ProSelect 27047 180KM
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441763 05/29/20 11:45 AM
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Triple_Se7en Offline
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Originally Posted by mbres2000
I have 4 qts of Castrol GTX synthetic blend and 1 qt of Mobil 1 left over from previous oil changes. Both are 10W-30. Any problem mixing those together in an old Chevy 350 in which I've been running a variety of oils and weights from 5W-30 to 10W-40, both conventional and synthetic?

You did good. This blend provides you with 20% less varnish accumulation, based on how GTX treated my engines during the late 80s thru mid 1990s..

Last edited by Triple_Se7en; 05/29/20 11:47 AM.

Stay Safe - Stay Healthy
Happy July 4th
Pennzoil Ultra Platinum // Mobil-1 EP // Valvoline Synthetics



Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441784 05/29/20 12:16 PM
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DavidJones Offline
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You do have a tow truck service on speed dial?


My garage.....2012 Toyota Highlander (wife's), 2016 Ford 2.7EB F150(mine), 1969 Pontiac GTO, 2005 Double cab Tundra(son), 2015 Honda Accord EX(son).
Re: Castrol / Mobil 1 blend? [Re: Triple_Se7en] #5441793 05/29/20 12:24 PM
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kschachn Offline
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Originally Posted by Triple_Se7en
You did good. This blend provides you with 20% less varnish accumulation, based on how GTX treated my engines during the late 80s thru mid 1990s..

What?


1994 BMW 530i, 253K
1996 Honda Accord, 289K
1999 Toyota Sienna, 437K
2000 Toyota ECHO, 290K
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441813 05/29/20 01:03 PM
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FordSVTGuy Offline
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popcorn


2012 Ford Focus S
2015 Lincoln MKC 2.3L
2017 Ford Explorer XLT
2014 Ford Focus SE Hatchback-5 speed
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441826 05/29/20 01:28 PM
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555 Offline
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Do it. Especially considering you're putting the mix in an "old 350".


84 XJ6 M1
92 Mustang 5.0 Redline
99 Tahoe 2 door Castrol Edge
99 MX5 Miata Anniversary Edition M1
04 Subaru STi Motul
Re: Castrol / Mobil 1 blend? [Re: mbres2000] #5441914 05/29/20 03:56 PM
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csandste Offline
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I'd do it. You do it.


2017 Kia Soul+ Valvoline Daily Protection 5w30+ a bit of Harvest King syn 5w30-- 75,000 miles
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