I was looking up Comp 2 and found this. Interesting to note that new Comp2 is not the same as old Comp2 which has been rebranded as a "Classic" oil. According to Fuchs, the new version is a low-smoke oil and doesn't lubricate as well due to the thinners in it.
Q. I have been successfully using Comp 2 Premix in all my 2T trials bikes for many years with no problems, and feel that posts like this:
http://www.trialscentral.com posting tend to confuse people, as in effect a lot of what gets posted is complete nonsense! I wonder if you would be good enough to provide some definitive and accurate information about 2T oils and ratios suitable for trials (I use 70:1 in old air cooled motors), that I could use on my web site (
http://www.classictrial.co.uk). This might help to reduce the amount of nonsense that gets posted about oils, and provide some accurate info at the same time.
A. Chris, I do not need to tell you that much, trials riding is at low engine output, so not much oil is needed; also, oil tends to accumulate in the crankcase due to low gas speeds, so extra lubrication is there if a sudden burst of power is required. (....but too much can foul plugs!) This is not too different from 2T riding in a crowded urban environment, for which the 'low-smoke' oils were originally developed. These give a clean engine and exhaust and virtually complete freedom from plug fouling, but they are not, in their basic form, a 'competition' or 'racing' oil. (The well-known Japanese 'JASO FC' low-smoke specification is based on tests in scooter and static generator engines. It also includes engine cleanliness requirements.)
All genuine JASO FC low-smoke oils contain a lot of thick polymer called 'PIB', (Poly-isobutene), so they have to be thinned down with a solvent, usually kerosene. The rest of the blend (in a basic type) is mineral oil and detergent/dispersant and anti-wear compounds. This makes them less effective lubricants than a NON-low smoke solvent-free racing oil such as Comp-2 Pre-Mix, so mix ratios for trials in A/C engines need to be around 30:1 to give equivalent lubrication to Comp-2 P/M at 70 : 1. But, both oils are detergent and give a clean engine, unlike castor-based blends, which are NOT detergent, and tend to leave a lot of carbon on the piston, ring groove and exhaust ports especially if used at low revs. We sell what is effectively an R30 (PRO-KR2) which is intended for Kart racing and similar 'flat-out' competition. Under such conditions it is reasonably clean-running, because it is part synthetic and doesn't behave like the old 1950s castors, which are still a 'folk memory'! I would definitely not recommend castor-base oils for trials, but if someone is determined to do so for the sake of the smell, they could perhaps get away with KR2 at around 60:1, increasing the amount for heavy going such as dry sand, and reducing it for walking-pace 'balancing act' sections at low revs.
News item!:
The new Comp-2 is a 'JASO FC Plus' low-smoke type, with some synthetic content. The old Comp-2Pre-Mix will be re-introduced in the 'Classic' range under another name, due to popular demand.
Regards
Oil Clinic Team