9-5 questions on engine oil

I've had no qualms flushing my 9000 either. Why are you concerned here ?

Maybe someone would care to comment on the relative merits of flushing oil vs a flushing additive ? In the case of the first you drain the old oil, refill with flushing oil, run the engine for a while, drain again and then complete the oil change as normal. The additive of course is simply poured in and the engine run for a while before performing the oil change.

Instinctively, I reckon the flushing oil must do a more complete job.

Graham

I can't see any problem with that.

Why 0-40 or 5-40 ?

I think you're fretting overly. You say you think it's got fully synth in there already. Replace with the same I'd say.

Graham

I use Halfords 5W/40 fully Synt for my 9000. Why? Because they sometimes have BOGOF offers near public holidays. The first number 5W is good for cold winter starting, the lower this number the better. The W letter actually stands for "Winter" from the days when people changed oil for the season. The only snag is that the larger the multigrade range, the more additives they have put it. And additives can wear off, thereby reducing the lifespan of the oil, though this is hearsay and probably not important as I change oil at 3000-4000 miles.

But oil types is a long discussion; don't confuse multigrade with multi- viscosity. The point of multigrade is precisely to reduce the viscosity variation with temperature. A uni-grade oil will have a large (standard) viscosity change with temperature, the 'grade' definition goes back to the 1920's.

How cold does it get in winter where you are ?

Graham

It doesn't get very cold here, only around freezing and very little snow. (south UK). The 5W/40 for fully synt oil is very common, whereas the 0W/40 (mobil) is more expensive. There is an argument against extreme multigrade for warm tropical climate or for vehicles which runs the whole day. e.g. busses. Then it's probably an advantage to rely on fewer additives for the longevity of the oil.