Planning to change my oil this weekend and just bought the 5 quart jug of Mobil1, fully synthetic. Just wondered if I have an extra bottle of 10W-40 lying around it will hurt anything if I mix it with the 5 quart jug of 5W-30?
I need a total of 6.1 qts., and I hated to pay the $12 for another single quart.
'02 V70 (Oil viscosity)
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Mr. Detail
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- volvolugnut
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Never recommended to mix viscosity. Just go buy another quart or another 5 quart jug.
volvolugnut
volvolugnut
The Fleet:
Volvo: 2001 V70 T5, 1986 244DL, 1983 245DL, 1975 245DL, 1959 PV544, multiple Volvo parts cars.
Mercedes: 2001 E320, 1973 280, 1974 280C, 1989 300E, 1988 300TE, 1979 300TD, parts cars.
2009 Smart Passion
Ford: 1977 F350, 1964 F150 (2), 1938 Tudor Sedan
Farmall tractors: 1956 400 Diesel, 1946 A
John Deere 214 lawn tractor about 1977 model
And others.
Volvo: 2001 V70 T5, 1986 244DL, 1983 245DL, 1975 245DL, 1959 PV544, multiple Volvo parts cars.
Mercedes: 2001 E320, 1973 280, 1974 280C, 1989 300E, 1988 300TE, 1979 300TD, parts cars.
2009 Smart Passion
Ford: 1977 F350, 1964 F150 (2), 1938 Tudor Sedan
Farmall tractors: 1956 400 Diesel, 1946 A
John Deere 214 lawn tractor about 1977 model
And others.
- Krons
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I’ve done it many times. You can do the math to determine the viscosity change. I’ve even topped with Delvac 1300 15w40 ($14/gal at Walmart) during the summer. Not probably the best if you want to run extended drain intervals but for my 5000 miles or less I’m not concerned. I’d be more concerned diluting the additive package vs the viscosity.
From my 08 S60 2.5T:
From my 08 S60 2.5T:
08 S602.5T/05 XC902.5T/02 S602.4T
08 C702.5T (sold)
05 S402.4i (RIP, timing belt failure)
The non-Swedes:
25 Mazda MX-5 / 17 Frontier Pro-4X / 17 Ford Focus
17 R1200GS / 15 Versys 1000 / 11 DR-Z400S
08 C702.5T (sold)
05 S402.4i (RIP, timing belt failure)
The non-Swedes:
25 Mazda MX-5 / 17 Frontier Pro-4X / 17 Ford Focus
17 R1200GS / 15 Versys 1000 / 11 DR-Z400S
- abscate
- MVS Moderator
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Just try to stay in one brand when mixing.
Don’t mix Shell and Mobil brand oils

Don’t mix Shell and Mobil brand oils
Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 XC90-in-Red
Link to Maintenance record thread
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 XC90-in-Red
Link to Maintenance record thread
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Mr. Detail
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You guys are great! Thx.
- Krons
- Posts: 1113
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And the testing has been done for you.
08 S602.5T/05 XC902.5T/02 S602.4T
08 C702.5T (sold)
05 S402.4i (RIP, timing belt failure)
The non-Swedes:
25 Mazda MX-5 / 17 Frontier Pro-4X / 17 Ford Focus
17 R1200GS / 15 Versys 1000 / 11 DR-Z400S
08 C702.5T (sold)
05 S402.4i (RIP, timing belt failure)
The non-Swedes:
25 Mazda MX-5 / 17 Frontier Pro-4X / 17 Ford Focus
17 R1200GS / 15 Versys 1000 / 11 DR-Z400S
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