MULDERKE · Feb 23, 2022

Hello all.
Looking at the next service and getting the stuff together.
I still have a good few litres of Shell Helix 5w40 fully Synthetic left from the annual oil change done every April. I do 5, thou tops a year.
My question is, can I get 5w40 fully synthetic of another brand and mix them without compromising the oil?
I doubt you can put fully synthetic with non synthetic etc, and would not anyway.
Just a question of whats a good option to do.
All opinions welcome.

Cheers all. Gary

lynall · Feb 23, 2022

I have mixed oils before with zero issues, I would say so long as new oil is the same ACEA spec as the stuff you have then it wont be an issue.
You can mix mineral with syn, all it does is bring the overall spec of the engine oil down to mineral spec.

Just think what you average car owner sticks in their engine, it will be the cheapest going, and so long as it says 5/30,5/40/20/50 they wont care, many wont even care about the viscocity!

Stv123 · Feb 23, 2022

If you ran low at a motorway service station it is unlikely you would know or be able to get exactly the same oil as you have already. as I understand it the fully synthetic oil just means it has been processed twice so it is purer. Any oil is better than no oil! The thinner oils were developed to reduce the drag created by the oils and therefore reduce fuel consumption figures. Bearing clearances were reduced so that thinner oil may be used. I normally change my oil twice a year putting slightly thicker oil in for the summer. I don’t seem to have any problems. Oil comes out pretty black even after 5k so 10k even for an oil that has been processed twice is a big ask.

Nodge68 · Feb 23, 2022

MULDERKE said:
My question is, can I get 5w40 fully synthetic of another brand and mix them without compromising the oil?

Yes, as long as the oil are the same type (synthetic, mineral, or part synthetic), are the same viscosity, and meet the same specifications, C1,C3 etc.

MULDERKE · Feb 24, 2022

Nodge68 said:
Yes, as long as the oil are the same type (synthetic, mineral, or part synthetic), are the same viscosity, and meet the same specifications, C1,C3 etc.

Thanks.
And thanks for all replies.
cheers

lynall · Feb 24, 2022

Stv123 said:
If you ran low at a motorway service station it is unlikely you would know or be able to get exactly the same oil as you have already. as I understand it the fully synthetic oil just means it has been processed twice so it is purer. Any oil is better than no oil! The thinner oils were developed to reduce the drag created by the oils and therefore reduce fuel consumption figures. Bearing clearances were reduced so that thinner oil may be used. I normally change my oil twice a year putting slightly thicker oil in for the summer. I don’t seem to have any problems. Oil comes out pretty black even after 5k so 10k even for an oil that has been processed twice is a big ask.

I think min/semi syn and syn oil are all mineral base oils with different additive packages, true syn oil is very expensive.

If you ever get really bored and maybe suicidal have a google for ACEA ratings and have a read, stimulating stuff!

K14 · Feb 24, 2022

I have done what your suggesting many times with no issues. I have never heard of a reason why it should be a problem.

MULDERKE

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lynall

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Stv123

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Nodge68

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MULDERKE

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lynall

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K14

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