Mixing Different Graded Oils

[MakaveliX]

I have a Mazda 3 which according to the manual can use 0w20 or 5w30

The oil is nearing the half way mark so may look at topping it up soon.
My concern is that it may already have some 0w20 oil already in it ( from when Mazda serviced my car before I purchased it )

In this case, is it safe to top it up with 5w30 ?

It's anyone's guess if it currently has 5w30 or 0w20 already in it - hence the question is it safe to potentially mix the two. ?

Thanks

Second question: At which point do you guys personally top up the oil ? Half way, Quarter away from the bottom of the dipstick ?

Edited by MakaveliX on Saturday 18th March 06:55

[Spitfire2]

It is fine.

[Kuwahara]

Any oil is better than no oil…

[dontlookdown]

Fine to mix those two at a top up. Then change for a known single grade at next oil change.

[E-bmw]

dontlookdown said:

Fine to mix those two at a top up. Then change for a known single grade at next oil change.

I assume you mean "change for a known multigrade" as both of those are multigrade oils, hence there being 2 grades in the type.

[PaulKemp]

“ Second question: At which point do you guys personally top up the oil ? Half way, Quarter away from the bottom of the dipstick ?”

If I check it and it’s lower than max I’ll top it up, only takes a moment.
My 170,000 Mike Fiesta ST150 has variable oil consumption so I check regularly, always before a long run but my tactic is that if I’m in a screaming hurry I won’t worry about level below max by ¼ but will top up at earliest opportunity

[dontlookdown]

E-bmw said:

dontlookdown said:

Fine to mix those two at a top up. Then change for a known single grade at next oil change.

I assume you mean "change for a known multigrade" as both of those are multigrade oils, hence there being 2 grades in the type.

It's a fair cop;)

[TwinKam]

PaulKemp said:

“ Second question: At which point do you guys personally top up the oil ? Half way, Quarter away from the bottom of the dipstick ?”

If I check it and it’s lower than max I’ll top it up, only takes a moment.
My 170,000 Mike Fiesta ST150 has variable oil consumption so I check regularly, always before a long run but my tactic is that if I’m in a screaming hurry I won’t worry about level below max by ¼ but will top up at earliest opportunity

This^^
Oil has a cooling function in addition to lubricating. The oil pump and bearings won't 'know' if the level is low ...until there's nothing to pressurise... but the oil itself is getting less 'down time' cooling off in the sump before it is sucked up and circulated again.
Why would you ever not want the level at 'max'?

[PositronicRay]

TwinKam said:

PaulKemp said:

“ Second question: At which point do you guys personally top up the oil ? Half way, Quarter away from the bottom of the dipstick ?”

If I check it and it’s lower than max I’ll top it up, only takes a moment.
My 170,000 Mike Fiesta ST150 has variable oil consumption so I check regularly, always before a long run but my tactic is that if I’m in a screaming hurry I won’t worry about level below max by ¼ but will top up at earliest opportunity

This^^
Oil has a cooling function in addition to lubricating. The oil pump and bearings won't 'know' if the level is low ...until there's nothing to pressurise... but the oil itself is getting less 'down time' cooling off in the sump before it is sucked up and circulated again.
Why would you ever not want the level at 'max'?

One of my cars would quickly drop from max to middle the settle there.

[finlo]

PositronicRay said:

TwinKam said:

PaulKemp said:

“ Second question: At which point do you guys personally top up the oil ? Half way, Quarter away from the bottom of the dipstick ?”

If I check it and it’s lower than max I’ll top it up, only takes a moment.
My 170,000 Mike Fiesta ST150 has variable oil consumption so I check regularly, always before a long run but my tactic is that if I’m in a screaming hurry I won’t worry about level below max by ¼ but will top up at earliest opportunity

This^^
Oil has a cooling function in addition to lubricating. The oil pump and bearings won't 'know' if the level is low ...until there's nothing to pressurise... but the oil itself is getting less 'down time' cooling off in the sump before it is sucked up and circulated again.
Why would you ever not want the level at 'max'?

One of my cars would quickly drop from max to middle the settle there.

Yeah that's because of the hole in the side of your sump!;)

[GreenV8S]

Mixing similar grades of oil from the same brand won't be a problem. Mixing different brands of oil introduces the risk that their additives will not work well together. But all these issues are insigificant compared to the harm of the oil level being too low.