Oil Change - flush?

[lard]

Hi,

After a bit of advise prior to changing my oil please,

I've got semi-synthetic in the engine at the moment and want to remove this and put in Morris 30 (also contaminated with fuel after a pump change so need to change it anyway)

I want to make sure that I'm going to get all the old synthetic type out before replacing with mineral - what's the best way? I was thinking of using morris's engine flushing oil, so run up to temp - drop the old oil - run with the flushing oil for 10 mins - drop this and put in the new

Only concern is that flushing oil contains detergent e.t.c. - wouldn't like to upset anything - is it worth using or will I be able to clear out the old oil by just dropping old oil whilst warm, changing once with mineral and then repeating again for good measure?

Thanks,

Larry

 

[faux]

If the oil has been contaminated with petrol it should be pretty thin anyway. I would just drop the old and put in the new. Also I was told that by flushing the engine you can unplug any small holes :mrgreen:

I'm not really an engine man, just what I would do.

 

[Pete B]

I am wary of flushing oils, too easy to disturb stuff you don't want to disturb! I would warm it up, drain then refill with mineral, then repeat the process.
I also would use a multigrade, 20W/50 or 15W/40 rather than a monograde. The monograde/multigrade debate has been running for years, and my view is a multigrade covers a variety of temps/situations, it is a progression over monograde and even VW themselves recomended multigrade from some point in the '70s. Just my opinion.
Think you are right to get rid of the semi-synthetic, along with fully synthetic, I understand that they are less able to dissipate heat than a mineral oil, rather important on an air cooled engine!

 

[BJ1]

Never ever think of using flushing oil in a VW aircooled engine :evil:

Much of the debris from general engine wear ends up as a sludgey gritty layer in the bottom of the case. Flushing oil is a very high detergent thin oil that neatly lifts this layer straight into your bearings. It then acts as a fine grinding paste and wears the white metal very quickly. Result - low oil pressure and knackered engine. I made this mistake about 35 years ago and (unlike some of my other mistakes) actually learnt never to do it again.

BTW there is no advantage to using straight 30 oil over a good 15/40 multigrade (winter) or 20/50 (summer) although it can be cheaper.

 

[lard]

Thanks for the advice guys - had a feeling flushing might be a bit over the top so glad to learn from others experience! I'll do a double change to make sure I get it all out,

Cheers,

Larry