Engine oil, mixing brands/grades?

Engine oil, mixing brands/grades?

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J4CKO

Original Poster:

41,677 posts

201 months

Tuesday 26th March
quotequote all
Going to do an oil change on my car, was about to order the oil and filter but then remembered I had some left of the correct 20w 50 Castrol from previous changes and top ups, about 2.5/3L.

So, do I buy a fresh 5L pack or use what I have and some of the other Synthentic oil, which is a VAG/Merc spec Castrol 20 W 30 hanging round.

Will it make any actual difference, car is a 2015 Fiesta ST.

Its not the cash, but it is like £40, its just partly down to decluttering my garage with its selection of 9 or 10 containers of oil.

My thoughts are, it will be fine, its fresh, clean fully synthetic oil, it does maybe 5k a year, so will likely do it anyway, just interested as to any thoughts as to why it may be a bad idea, you take a car to a garage and they tend to plonk whatever they have in.

Found some from 2005, 1L top up containers, does engine oil ever go off ? That will do for the mower.

J4CKO

Original Poster:

41,677 posts

201 months

Tuesday 26th March
quotequote all
E90_M3Ross said:
Just use the correct grade and spec for the car. It would probably be fine, but I personally wouldn't use anything other than manufacturer approved and recommended.
Nah, its getting whats there, its a ten year old Fiesta, just interested to what could possibly happen rather than "Just do it m'kay".

Ford thought the Mustang MachE was a good idea so not that bothered what they say.


J4CKO

Original Poster:

41,677 posts

201 months

Tuesday 26th March
quotequote all
jhonn said:
20/50w? Did you mean to type 5/20w?

I have mixed oils from different manufacturers in the past but tend to stick to the same viscosity/ACEA grade. For a routine oil change in your Fiesta I wouldn't mix 5/20w with an appreciable amount of 5/30w. I'd chance a small top-up if I had to, but no more than 1 litre (assuming they both met the same classification).
Why though ?

What could happen ?


J4CKO

Original Poster:

41,677 posts

201 months

Tuesday 26th March
quotequote all
Yeah its all modern synthetic, not old school stuff, I typed it wrong

J4CKO

Original Poster:

41,677 posts

201 months

Tuesday 26th March
quotequote all
SAS Tom said:
I wouldn’t risk anything but the correct oil on an ecoboom. Having said that it’ll more than likely blow either way.
Though the engine is listed as an Ecoboom/boost, its not the ones that typically give trouble being the 1.6 four, and not the 1.0 triple, these are typically pretty reliable, and its running 50 percent more power than normal as well, and has been for a couple of years, and a track day.