Mixing semi-synthetic oil with fully synthetic

[DAKA]

I currently run on semi-synthetic oil and I want to change to Fully synthetic , I dont want to flush the system so there will be a mix of the two oils

1 L semi and 11 L synthetic, obviously they will be the same grade and to manufactures spec or exceed spec.

Anyone know if there is a reason why you shouldn't mix the two ?

In my distant memory I remember reading you shouldn't mix mineral oil with synthetic ???????






Why I want to upgrade, I spoke to an engineer who said an engine had been run on synthetic oil and then semi drained.......it ran normally for 10 000 miles just on splash feed.

They then drained it completely and it ran normally for 1000miles
They then took the filter off and reved its guts out until it gave up 15 mins later......no idea just how scientific the experiment was but I only need my engine to run for 150nm between engine checks /forums/images/graemlins/smile.gif

 

[T43]

Hi Daka ! Firstly changing to fully synthetic you should flush system through, but I have to question any advantage of using fully synthetic oil in a low reving deisel engine.

The cost will be roughly 50% more and if you are changing it every season or 100hrs you will gain nothing in terms of reliability or engine life (unless of course you are concerned that one of your engines might dump all its oil mid journey somewhere). Hope this helps. /forums/images/graemlins/smirk.gif

 

[Kawasaki]

I don't think You will gain any advantage by switching to Fully Syn.
Semi, changed regularly with a new filter, whch You probably do anyway, is more than adequate for Your type of engines, imho

 

[DAKA]

Thanks T43 amd Kawasaki,
I will stay with the semi and save a few £££££££££s /forums/images/graemlins/smile.gif

 

[lewi]

in recent tests a truck engine was run on synthetic oil
for aprox, 1,000,000miles with no increase in wear rate,
the theory is reduced servicing costs,
fewer oil changes. you should only have to
change filters. oil that good should be
in all engines, at 100 hours a season, synthetic
oil should out last the engine,
result /forums/images/graemlins/wink.gif

 

[Kawasaki]

Not nescesarily so!
Here's an oily tale.
Nowt to do with boat/truck engines but anyhow.

During the 70's I was well into the Motorbike lark.
At the time the John Player Norton team were running Rotary (wankel tyoe ) motors.
Problems with the Tips (piston rings ) wearing arrived.
All sorts of boffins in the lube business were summoned.
Synthetics were tried to no avail.
In the end old fash Strait 30 did the trick!!

Maybe the latest cutting edge engines will like synthetic.
Older stuff, different tolerances and Technology maybe wont.
Anyway a Million miles, cripes We aint gonna do owt like that in our Mobos.
Ok for a vehicle that is running night and day.
Remember Mobos sit around a lot doin nowt.
So the qualities of the lube has different things to cope with.
The likes of DAKA's engines are pretty old hat techno wise.
Semi is a bit of a luxury for them anyway, cos when they were first designed (those Cummins- Mercruisers go back quite a while) Synthetic , even semi was new technology.
It,s about matching the eng to the oil.
Cripes I,m not starting on Oils, that's enough, I'd be at it all night /forums/images/graemlins/grin.gif