mono, multi or synthetic?

after three years and much money Im ready to flash up my 71.Les emery runs straight 50, Matt in colorado runs 20/50 castrol. I have spent hours researching this and have really come to no conclusion. Is there anybody out there that has put serious long distance miles on these commandos that is qualified to help? thanks

mcns said:

after three years and much money Im ready to flash up my 71.Les emery runs straight 50, Matt in colorado runs 20/50 castrol. I have spent hours researching this and have really come to no conclusion. Is there anybody out there that has put serious long distance miles on these commandos that is qualified to help? thanks

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i always thought that clean oil -AKA frequently changed - was essential

I run 10/60W fully syth Millers. No matter what the temp the oil stays the same consistancy.

My bike currently has Mobil 1 in it from the previous owner but it is VERY noisy with more rattles than a millionaires baby.
After looking around I was amazed at how little the 20w50 etc. labels resembled the actual viscosity of the oils that they were labelling.

I am probably going to try either Penrite HPR10Gas or Penrite Enduro in it.
The HPR10 Gas has a viscosity of 140 @ 40°c and 18.8 @ 100°c and 0.11% Zinc.
The Penrite Enduro has a viscosity of 284 @ 40°c and 28.8 @ 100°c and 0.176% Zinc.

Hopefully one of these will quieten it down.

I feel the same way about all this imformation that people give on their favorite oil for the commando engine. I have used 40w valvoline race oil for sveral months on my newly restored 71. I only chose this oil because several brit bike guys love it in their bikes. After reading some test results that have been posted on another site i will probably try redline 20-50w. I haven't had any problems with the 40w valvoline so i may be trying it for no good reason.

In the 1940s and 1950s when the ancestors of the Commando engine were conceived monograde oils were probably all that was available. Straight 40 grade for winter and 50 for summer. They are simple and predictable but you must let the engine thoroughly warm up before working it hard, since thick oil circulates more slowly and gives the engine poorer protection just at a time when it needs it most and maximum wear is taking place ie. from cold. No problem when warmed up. The engine also suffers slightly less from wet sumping than it would with multigrade oil.
Huge developments in oil technology have now created very competant multigrade oils which are capable of protecting our engines. The better multigrades use poly alpha olifin (PAO) ester based synthetics and are polar in nature ie. they are attracted to metal. They circulate better from cold than monogrades yet still handle stress at high temperatures.
From what I have deduced, the best multigrades of the ester variety are:-
Redline 20w/50
Motul 7100 4t 20w/50
Silkolene Comp 4 20w/50
Even Mobil 1 15w/50 is PAO only and does not have ester polar qualities.
All the multigrades wet sump slightly more but not enough to offset the considerable advantages in lubricity, film strength and stability.

I just purchased 4 quarts of redline 20-50w!!!!!!!! Let the test begin! I hope it helps the motor last a little longer. It sure isn't cheap, but this should be cheap insurance for a high dollar rebuild. I have also purchased a wet sump valve from cnw.

Steven. Always ensure that the oil feed pipe from the tank to the anti-drain valve is fully primed, particularly after you do an oil change. These valves stop wet sumping ok but can also stop all oil flow to the engine if you get an air lock or the valve sticks. I have not been brave enough to fit one and so put up with some wet sumping, albeit only slight, since I have a Mk3 timing cover with antidrain valve on the pump output side.
Also, if you have not yet run the engine since it's rebuild, refer to recent post on "Running in".