Before I change my son's oil.....

[randers]

Hi. My youngest has a second-hand Polo. It's telling him it needs an oil top up - he can't find out what type or grade of oil was used before, but can be pretty sure it wasn't done by a VW dealer so may not be the recommended one.
I assume I shouldn't take a punt on grade and just top up with eg 5w-30, in case it was something else before, therefore safest to change the oil? Similarly with type - no idea if it was semi-synthetic, mineral, or whatever, so should drain and replace?

And if changing it, is it enough to drain it or should flushing oil be used? Thanks - I'm grateful for your expertise!

 

[Burnerman]

Flushing oil really isn't needed these days, oil has enough detergent in it to do that for you.
Depending on the age of the car, it could use a 10/40 semi synthetic or more likely, a 5/30 fully synthetic as you suggest.
John

 

[JohnD]

flushing oil is not often needed, but if it is an old car, and you think it may have been neglected in the past, it's useful to loosen old sludge.

What colour is the existing oil on the dipstick? If still transparent, the engine must be fairly clean, because modern oils are detergent and will pick up dirt quickly. If somewhat dirty, give it an oil and filter change because you don't know when it was last done. A can of oil is not expensive.

I like to write the date and mileage on my oil filters when I put them in. You can make your own durable label with a couple of inches of vinyl tape and a permanent marker. Same with airfilters and antifreeze.

When it's working, this site has a lookup tool for recommended lube grade
http://applications.castrol.com/oilselector/en_gb/c/search
it tries to guide you to the more expensive options
but wilko and halfords own-brand are cheaper and fine for ordinary cars.

I always ask for grade 710, per the maker's guidance on the cap

710-cap

• JohnD
• 6 Mar 2017