Engine oil again!

[Peter Naulls]

I'm nervous about asking this because I suspect I'll get conflicting answers but here goes anyway!

Is there any reason why I shouldn't use synthetic engine oil? It was bought in error, believing it to be a re-branded version of the mineral oil I had used previously in my special. The engine has always used modern detergent multigrade oil since a comprehensive engine rebuild many years ago.

[Colin Reed]

HI PETER,
I am assuming you are running a full flow oil filter with detergent oil,
There would be no problem changing to fully synthetic oil.
I would run the engine to warm the oil , then allow all the oil to drain out , change or clean oil filter depending what type you have.
There will be no adverse effects and just keep using that brand in future.

Good luck and happy driving

Colin
NZ
(PS) A lot of the hype on oil is down to Brand loyalty.

[Peter Naulls]

Thanks for your reply Colin. 

I don't have a proper filter, just the conventional Austin set up but it has always had detergent oil for the last 25000 miles. Does that change your advice?  The old oil was Castrol Actevo 20W50 the new is Castrol Power 1 (JASO MA-2 (T903:2016):API SN)

I have always stuck religiously to the same brand, maybe unnecessarily!

[Reckless Rat]

If you intend to extend oil changes to 15,000 mile intervals, then use a synthetic. However it's expensive compared to mineral oil and personally I have thought about it but just use supermarket 20W50 and drain it every 1000 miles. Its my way of keeping the oil clean. I'd be interested though to hear whether there is any benefit to the lower viscosity of synthetic oil...

[Colin Reed]

HI Peter,
No it does not change my advice,
you have done a lot of miles with detergent mineral oil with no problems so synthetic will be no different,
just no need to change filter that has to be a saving.

Happy motoring

Colin
NZ
Hi Reckless The viscosity Is the same Regardless if mineral or synthetic 20W-50

[Peter Naulls]

Thank you Colin, that's great.

Reckless, the car is only ever used for infrequent local journeys. Last time I changed the oil was 2 years /1000 miles ago so cost and longevity are less important! I keep promising myself that next year I'll have more time to enjoy it ...

Peter.

[Reckless Rat]

One of the reasons for going synthetic is, apart from the longer life, is to be able to use an oil with less viscosity, therefore less friction with the same degree of protection, hence the lower grading such as 10w40, 5w30 0w10 etc. Using a synthetic at 20w50 seems to defeat the object, surely?

[AustinWood]

We use 5W30 synthetic. Works well and the local motor factor does one very well priced. It's the same oil I use in my 1999 Citroen Xantia whit makes life simpler.

[Bob Culver]

Search is going to lead many here, so;

In days of old thick oil was used to moderate consumption, leaks, and noise. Also in the absence anti wear additves (ZDTP) reduced wear of cams. (in the 1940s my very fastidious and observant father used to change main bearings about every  2 or 3 years. He reckoned the cam followers wore more on 30 than 50, not that it matters.) Anti wear additives now mean a thin oil is fine. The crossover temp where 20W50 is the same as 30 is quite low, so many Sevens work hard stirring the oil. 
On early multigrades there was some question about how they behaved hot on rubbing services where it mattered, some claim a 10w30 hot behaved more as a 10 which is a bit thin. 
I presume this, and the fact cars do not start off piping hot,  has led to the racer boys establishing on  monograde 30.
However modern multigrades and certainly the expensive and synthetic ones behave more as their rating ie 5W 30 behaves hot as 30 under stress.
For the low loadings in a stock Seven engine anything modern is more than adequate. However debate rages around the degree of detergency esp with engines not fully cleaned out and without a filter. The degree to which sediments are dislodged is a puzzle.
Note VW Beetle used no filter. Many other cars in the 50s without filters transitioned to detergent oils without wholescale troubles.
I am sceptical  of classic oils. If truly so and merely API SB would be no better than the oils my father used in 1940s which resulted in 1/2 inch of grey sludge and mains rumble every 10,000 miles (lot of short runs), and rebores for all cars starting at 40,00. No one now runs sequence tests for the old API ratings. Suspect considerably exceed API SB.

[Colin Reed]

HI All,
Just to clarify some confusion.
The question that Peter Asked was as he has a new container of Synthetic 20W-50 could it be used in place of mineral oil in his Engine.
To which my reply Was YES,
I was not trying to start a debate on the different types and grades of oil.

The Reply from Reckless makes perfect sense and is what Peter has been doing for years

Apology to all for confusion

Cheers All
Colin
NZ