Semi Synthetic or organic motor oil?

[Drewtee]

I still don't know the answer to this question.

In the UK, the two top 113 specialists use different types of oil. one uses semi synthetic 10w 40 and the other uses organic. They are both renowned for their expertise on our cars. They both believe they are using the correct type of oil. I've also noticed this withother classic cars marques. Some specialists swear by the semi synthetic and others wouldn't dream of using it as the engines are not designed to use the modern stuff.

I know the thing about semi synth being hard on the seals but what are the benefits or not of using it. it is supposed to be better for starting up idle engines, Castrol GTx seems to be the oil of choice with the specialist  of different Marques using the semi syth.


Does anyone have any views on this, expert or not?

[DavidBrough]

I'm not sure there will ever be a definitive answer on this especially as the current experts don't quite agree. For my part I don't know much of the detail about current oils and what they are supposed to do other than the fact that they can be very expensive and last for 20,000 miles or so. Now I'm not that comfortable about leaving the oil in an old car for that long and prefer to change it quite regularly so I use the cheaper classic oils which seem to have worked very well in their day and so far work fine for me.

[Benz Dr.]

Everyone has a former life. I once sold synthetic motor oil.

 First of all, oil isn't expensive. If anything dino oil is getting that way relative to the premium stuff. Modern synthetic blends have everything you need and probably more.

The idea that our engines were never designed to run on synthetic oil is nonsense. They will, I know this for an absolute fact. They will also run OK on regular oil but you will need to change it more often.
My own car runs entirely on synthetic lubes; engine oil, power steering, trans and diff. Nothing leaks out and I change my engine oil every other year.
 Our combine runs on semi synthetic 15 W 40 and has since it was new back in 1983. At 4,500 hours it uses a litre every 7- 10 hours but it holds 22 litres. I've changed oil 8 times over those years. With conventional oil it would have been 45 times - that's a  lot of used oil!

If your engine leaks a lot of oil stick to the regular stuff.

[RickM]

Agree with Benz Dr.

Also, the term "semi synthetic" may be up for interpretation.
Here in the US it's legal to call molecularly modified "dino" oil, synthetic. In other parts of the world this isn't acceptable.  Is this what you speak of or a semi-synthetic "blend" where half is "organic", dino oil and the other half "synthetic"?

[Benz Dr.]

I believe it was half dino and the other half synthetic. At the time ( at least 25 years ago ) there wasn't really much on the market that could even come close to this stuff nor was there a lot to choose from.
It was marketed as 15 W 40 para synthetic sold by AMS/OIL.

[Drewtee]

Yes Benz Dr, i,ve heard that leaky engines should stick to mineral, also that synthetic is better for engine start ups.
Semi syth is a blend around 30% synthetic but adds the benefits of synthetic to the mineral base.
Seems that this blend could be a good thing.

I still don't understand why some garages are so anti the ' blend' way to go. 

 

[Benz Dr.]

It's a matter of economics. You can buy bulk oil and make a good mark up on it. Even in 20 liter pails it's considerably cheaper than one liter bottles but still a lot more than 45 gallon drums. Then you have all of those cans to throw away if you go a can at a time.

Bulk synthetic would be less costly but it would still cost more. You would only stock that in smaller containers for those who want it. Since most customers just want '' oil. ''  That's what they expect and the lower price that goes with it.
 So the place gives them their dino oil and hopes they come back in a few months for a fresh batch. As a retailer you won't make a lot more on the synthetic so having someone come back for service every few months for dino oil pays off.

If you own a fleet of cars or machinery then semi synthetic pays off in spades. It's amazing stuff!