Thread: Penrite semi synthetic two stroke oil

It won't matter in your brush cutter but the "really good stuff" is "fully synthetic oil" as opposed to semi synthetic oils.

There are all sorts of interpretations about this but here is my take on this topic
Standard two stroke oil uses a low cost refined mineral oil and a mixture of additives that suppress smoke and generally improve lubrication.

Semi-synthetic oils use a blend of refined mineral oils, a small amount of synthetic oil (manufactured, usually an "ester" based oil made by combing an acid and an alcohol), and a wider range of additives, some of which may be synthetic. This is done to save money because synthetic oil is relatively expensive. Because of thi,s the amount of synthetic oil in a semi synthetic can be quite low ie 5-10%. Penrite should be good but some lesser well known brands of semi synthetic two stroke lube are probably no better than a quality standard two stroke lube. If a low price is paid for a semi synthetic lube chances are it doesn't have much synthetic oil in it.

Fully synthetic oil uses a more carefully controlled blend of mineral oils, more synthetic oil and more synthetic additives. The amount of synthetic oil is never 100% as this would make it prohibitively expensive - typically for fully synthetic oils it's only 20-30%. Some racing two stroke oils also use vegetable oils like castor oil as the base oil. One problem with using castor oil i it will "gum up" the works so is only used in engines that are regularly rebuilt like racing engines.

In terms of why bother, here is a typical blurb form Synthetic Oil Vs. Semi Synthetic Oil: What's the Difference?

Compared to a mineral oil, full synthetic oils have a wider operational temperature range (performing well at lower temperatures as well as high temperatures), better shear stability, lower toxicity, lower deposit formation and are less volatile while still being compatible with mineral oils.

Another benefit of using fully synthetic oils in 4 stroke engines is they don't need to be changed as often.

One interesting thing about esters is they are what is responsible for the fruity smell/taste of most fruits. They too can also be "manufactured" and are used in articifical flavourings

I know it's not as good as the fully synthetic, but it'll be better than normal oil.
I was using Castrol 2T which I'm guessing is a mineral oil - I say guessing as the castrol website is crap and I couldn't find any specs on the stuff.

Originally Posted by smidsy

I know it's not as good as the fully synthetic, but it'll be better than normal oil.
I was using Castrol 2T which I'm guessing is a mineral oil - I say guessing as the castrol website is crap and I couldn't find any specs on the stuff.

For low stress engines run in moderate temperatures, even straight Mineral oil is fine, It's when thane engine is under severe loads and operating under very cold or hot conditions that the semi and fully synthetic stuff earns its keep.