G'day folks,
Great topic, I have used for a few years now Valvolene Marine 2 Stroke oil for air cooled engines. It was on special at Supercheap for around $22 for 4 litres. Used in my trimmer and all of my mowers. Especially good in the Victa Twin mixed at 25:1 for everything. I bought a new Rover/MTD blower at Christmas time and it came with a small bottle of synthetic oil to mix at 40:1 and it seems fine but once out of warranty it will go onto the Valvolene as well. I think I will keep an eye on the catalogues and when it’s on special again I will stock up.
Outboard oils aren't optimal for air-cooled 2-strokes, as they're formulated for the much lower running temps of once-through water-cooled outboards. Not to say that they won't work OK, but more carbon deposits are to be expected.
That said, back in the early 70s Mobilco used to recommend Castrol 'Super Outboard' oil for Echo 2-strokes, over their ordinary '2-stroke Oil' of the day.
Castrol Super TT superseded the Outboard oil for Echo gear, once it came on the market in the late 70's.
That one was essentially formulated for high performance two-stroke air-cooled motorcycle engines, and there were some quite large and powerful ones on the market at that time. The Kawasaki H4 750cc triple comes to mind...
I don’t see why you could not just mix straight 30 weight oil with unleaded to run two strokes on but mind you it’s dearer than two stroke oil anyway.
Umm, bad idea.
Modern 4-stroke oils contain over half 'additives', unlike in the 1950's when Victa used to advise the use of 'Castrol XL' oil - which was then almost straight mineral base stock oil.
Some of these additives [e.g. the anti-wear and dispersant components] leave a significant solid 'ash' residue when burned, which will tend to clag things up in time. Also, these oils are
not formulated to be miscible with petrol, and some of the additives won't stay mixed.
The synthetic 2-stroke oils do burn a lot cleaner, and can usually provide effective lubrication at much 'leaner' mix ratios.
IIRC the first synthetic 2-stroke oil that came on the Oz OPE market was the Optimol brand, introduced in the early 1980's by Canning & Son of Hawthorn, Vic. This stuff wasn't cheap on a $/L basis, but the ability to run 50:1
or leaner mix [which was unheard of with the mineral 2-stroke oils of the day] substantially offset that.
To run the very lean mix, it did need to be used with a carby with mixture adjustments [on OPE, these were the Tillotson, and later Walbro and Zama etc. diaphragm carbies], and this is still the case.
Varying the proportion of oil in the fuel mix does affect the fuel/air ratio going into the engine, so correction is required. All else being equal, leaner on oil = richer fuel/air ratio.
