What engine oil viscosity and why

[5harp3y]

Decent 5w-30

BMW know what to spec and stick with that. if you need a heavier oil its masking another problem / somethings worn and needs seeing to

also i wouldnt bother with any oil additives

 

[colb]

Nothing wrong in treating it to a flushing addative prior to draining and changing oil and filter, it should get rid of any varnish build up within the internals. Follow the makers instructions, usually just add the contents to the engine and run it up to temp, give it the time to circulate as advised on the tin to do its job. Drain and change the filter replenish with new oil, the grade for your car.

 

[Pingu]

Your car shouldn't need additives. If it does, it's getting too old and worn to bother what brand you put in it, as long as it's the correct grade.

I have never flushed a car, but I've flushed many van oil changes. The van gets stuff costing £2 per litre, the car's get stuff costing £6 per litre.

 

[Sean d]

Your car shouldn't need additives. If it does, it's getting too old and worn to bother what brand you put in it, as long as it's the correct grade.

I have never flushed a car, but I've flushed many van oil changes. The van gets stuff costing £2 per litre, the car's get stuff costing £6 per litre.

Who's talking about additives, I only asked what grade and why, however it will get flushed

 

[Pingu]

It was a reply to colb, but...

Flush is an additive. It is a very thin engineering oil (similar to 3-in-1) and has additional detergents in it. It is very good at cleaning a dirty engine. The point I was trying to make is that your engine shouldn't need it.

https://blog.amsoil.com/is-an-engine-flush-good-or-bad/

If it does, it suggests that your engine has not been looked after. If that's the case, the damage may have already been done and the bearing clearances are already out of tolerance. In which case, you may want to use a thicker oil.

As the article says, an engine flush can save an engine, but if the engine is an old rattler, it can be bad for it.

I'd ask myself the question "what am I trying to flush out of the engine"? If you have used poor quality engine oil (an oil that hasn't cleaned the engine as it works), use a flush. My van uses 10W-40 that I can get 20 litres for £40 (£2 per litre). I use a flush on my van as it's not a performance engine (40bhp per litre) and rattles like a tin can.

My Smart car and BMWs have relatively high performance engines (approaching 100bhp per litre) and use Mobil 1 costing £30 for 5 litres (£6 per litre). The oil has enough detergent in it to clean the engine as it works and doesn't need a flush. You can tell this by how clean the engine is under the cam cover.