Which semi-synthetic oils are good
 

I've seen semi-synthetics (blends) on the market for some time, but have not seen any literature as to the amount of syn/dino in the blends. Are they 10/90, 30/70 or 50/50? Certainly the type of synthetic base (polyol ester,) the amount of Polymeric thickeners(the stuff that breaks down at high temperature to form varnish in your engine) and quality of the dino base are all factors to consider. Anybody knowledgable about these blended synthetics? Roger

Synthetic oil

A lubricant produced by synthesis rather than by extraction or refinement, and as a result of the synthesis, the molecular structure can be precisely arranged to meet the manufacturers' criteria for high performance engines. Synthetic lubricants are manufactured from a number of differing chemical bases, and several classes of compounds have been developed to provide base stocks for commercial synthetic fluids. Synthetic fluids are knows a Polyalfaolefins (PAO), poly esters, poly alkaline glycols (PAG), silicones, silicate esters, phosphate esters, fluoro carbons, etc… Synthetics lubricants frequently satisfy special requirements such as non-flammability, thermal stability, resistance to oxidation and radiation much better than mineral oil products. Also the urgency to the concept of environmental responsibility has led to the increased development and need for functional fluids that are both biodegradable and low in toxicity. A mixture of mineral and synthetic base fluids is often used to formulate high performance lubricants

Blended Synthetic oil Follow-up
 

My quick research found this information about "Blended" Synthetics.

Synthetic Blend - a Hype?
In recent years a new category of Motor Oils has been developed primarily in the USA, they are "Synthetic Blend" Motor Oils.

They are about half the price of "Fully Synthetic" motor oils which currently sell in the $4.25 to $5.00 price range for one U.S. Quart.

They promise the same performance as "Synthetics" but for half the price.
At first glance that seems promising, but when the truth of "Synthetic Blends" is examined, it is apparent that the only benefit that they offer is a higher profit margin for the marketer of the oil.

Here are the facts:

"Fully Synthetic" Motor Oils contain 70% to 85% Synthetic Base Oil by volume, the balance are additives dispersed in Petroleum Carrier Oil. They sell for under $5.00 per US Quart and cost about $3.25 to manufacture. The mark up is about 50%. The market share is about 4%.

Petroleum Motor Oils contain 80% to 95% Petroleum Base Oil by volume, the balance are additives dispersed in Petroleum Carrier Oil. They sell for about $1.00 per US Quart and cost about 35 cents to produce (even at price of crude oil @ $30.00 per barrel). The mark up is about 150%. The market share is over 90%.

"Synthetic Blend" Motor Oils contain 5% to 20% Synthetic Base Oil, 60% to 70% Petroleum Base Oil, the balance are additives dispersed in Petroleum Carrier Oil. They sell for $2.00 to $2.50 per US Quart and cost ONLY about 50 to 60 cents to produce. The mark up is 300%.The market share is about 2%.

The temptation of high returns on investment which is presented by "Synthetic Blend" Motor Oils is the only driving force behind their promotion, after all if you could double your profit, what would you rather sell "Petroleum" or "Synthetic Blend"?

Even Mobil, which for over 20 years held the position that "semi-synthetics" as they used to call what now is generally referred to as "Synthetic Blend", are a waste of money, if you want synthetic quality and synthetic performance get "100% Synthetic*" (Mobil 1, of course).

But now under the pressure of Exxon management since Mobil was merged into ExxonMobil,
guess what the latest news is: "Mobil 1 Synthetic Blend" !!!

"Synthetic Blend" is a hype, if you think that you can not "afford" synthetic oil, get petroleum oil and change it frequently.

SEEMS TO ME THAT IF YOU WANT A BLEND - MIX A FULLY SYNTHETIC QUART TO EVERY 3-7 QUARTS OF DINO OIL!

Roger