"Full" Synthetic vs. "Semi" Synthetic

[BrocLuno]

Yeah, could be ...

But Isosyn oils are some good ones no matter how they make them. Always worked well in my stuff

 

[pscholte]

I fall back on my belief that engine oil is such a small piece of the total cost of operating a vehicle and has such potential impact on longevity that I will spend whatever it takes for the highest spec'd Syn. I am not so callous as to disregard the high cost of Syn in Europe or Oz but were I there (I used to live in Europe) I would still pay the price. We spend money on so many non-essential activities that there are other places to cut back.

 

[alarmguy]

Originally Posted By: Thugzy
So if marketed "Full" Synthetic engine oils are not a base stock man made synthetic, then what is the difference vs. a "Semi" Synthetic?
I understand there may be different levels of additives between the two, but what really gives?

What is the point of a semi?



Ill get flamed for saying this, it doesnt matter, they all meet the current API for whatever it is you need. Conventional Semi or Full synthetic (which is just highly refined plain old oil) if it meets the API that the maker of your engine requires, you are good to go and the engine will outlast the car or truck.

OIL IS ALL ABOUT MARKETING = BEST MARKETING = BEST PROFIT

With that said, yes, I do believe there are some better quality oils out there but its any ones guess which one will give you less wear as NONE of them provide the proof. Also, I firmly believe most of the best wear oils are just as equal weather conventional, Semi or Full syn. There are good from every category. Again, if it meets the API for your vehicle, as boring as that is, your good to go.

As someone else posted, yes, I do feel a bit better going with big companies, be it, Mobile, Citgo, Chevron, Shell, Valvoline etc, etc. Unless otherwise proven.

 

[SonofJoe]

Originally Posted By: alarmguy
Originally Posted By: Thugzy
So if marketed "Full" Synthetic engine oils are not a base stock man made synthetic, then what is the difference vs. a "Semi" Synthetic?
I understand there may be different levels of additives between the two, but what really gives?

What is the point of a semi?



Ill get flamed for saying this, it doesnt matter, they all meet the current API for whatever it is you need. Conventional Semi or Full synthetic (which is just highly refined plain old oil) if it meets the API that the maker of your engine requires, you are good to go and the engine will outlast the car or truck.

OIL IS ALL ABOUT MARKETING = BEST MARKETING = BEST PROFIT

With that said, yes, I do believe there are some better quality oils out there but its any ones guess which one will give you less wear as NONE of them provide the proof. Also, I firmly believe most of the best wear oils are just as equal weather conventional, Semi or Full syn. There are good from every category. Again, if it meets the API for your vehicle, as boring as that is, your good to go.

As someone else posted, yes, I do feel a bit better going with big companies, be it, Mobile, Citgo, Chevron, Shell, Valvoline etc, etc. Unless otherwise proven.



There was a time when I would have 100% agreed with the above, especially the bit about if it meets the spec, you're good to go. Now, with the benefit of having a few years to reflect on how oils are formulated, I'm not so sure.

First, you need to realise the API, the oil companies, the additive companies, etc are not your friend. Indeed even though you might actually buy your oil, you are never considered to be 'the customer' (the OEM is). So you get what us good for them, not necessarily what is good for you.

Consider this...API engine oil testing covers just one OCI. Admittedly it's a severe service OCI but it is just one. Anything that carries over from one OCI to another or is a slow developing, cumulative problem ISN'T tested for. Given that a US car might have thirty OCIs over it's life time, don't you find that just a little bit odd?

Also just think about that 15% max Noack spec in GF-5 that's going to carryover unchanged in to GF-6. In Europe, that would be considered laughably high. Read BITOG and you will see lots of 'my car is x years old and it started to use oil' posts. Did you know that oil consumption isn't really tested for in the API test sequences other than the 90% max limit on the IIIG? The Noack spec should be coming down to minimise oil loss but it isn't because the oil companies need it this high to allow Group II oils to make US 5W30's.

You might want to reflect on this next time you're in Walmart and deciding whether you want to buy full mineral, semi synthetic or full synthetic.