Charon wrote on 10/14/09 at 13:20:54:Remember too that the ZDDP only comes into play when the oil film has broken down. It protects against metal-to-metal contact, and as long as the oil film is intact there is no metal-to-metal contact.
Charon is correct, ZDDP is an extreme pressure additive that puts an impervious surface layer on steel that will resist galling and abrasion when an oil film breaks down. Momentarily, anyway.
Where does this oil film breakdown happen in a Savage? Cam lobes and tappets, pin/plate junctions in the cam chain, cam journals in the head, flank surfaces of the highly loaded gear teeth, skirt of the piston rubbing the cylinder wall -- in short all the locations that extreme wear and galling damage shows up in our engines.
Will the ZDDP layer protect an engine in case of a lag in oil pressure at start up (zero oil pressure) or a momentary oil film loss during full speed running? Yep, a ZDDP film will protect a smooth steel surface for a minute or so until it is worn away. Generally you get oil pressure in less than 10 seconds after start up so this is a moot point if you have a ZDDP containing oil. Remember, the ZDDP surface layer gets refurbished by the oil and quickly gets back up to its normal microscopic thickness in time to withstand the next assault.
Protracted high speed abuse will go thru the oil film and thru the ZDDP layer inside 2 minutes and start causing wear and damage (if you think you need extreme temperature protection, please consider a Syn oil with extreme protection levels). I go this route as I am a confirmed "wicker".
Why is ZDDP so important that the high performance engine world has howled at its removal or dilution to less than 10 PPM levels?
Because unless a motor was redesigned to use modern oils (with extreme pressure additives removed to keep from killing catalytic converters) it HAS to have ZDDP to live a full life. Most older designed engines were developed and tested using motor oils with over 10 PPM of ZDDP in them -- engines that had some "heavily loaded" design spots in them that were carried along by the ZDDP film provided by old additive rich oils so the designers never saw any test or wear issues with the design -- until EPA regs took the ZDDP out of the oil and the galling and rapid wear reports started at the hot spots. Old design engines are dying because of "bad oil".
Our Savage engine have these hot spots in it -- we are an old design engine and we must have our ZDDP or we get galling and relatively rapid wear in these areas when our oil films break down due to heavy loads or high temperatures (or both).
Remember, we have an air cooled engine with ZDDP hot spots in it and an oil pump that is "just enough" to do the job with the old type oils.
Should our members be using modern "ordinary car oils" that have been neutered by the EPA in their Savages?
No -- they should use either a motorcycle specific oil or one of the known good diesel truck oils that all have the necessary ZDDP additive packages combined with an oil weight and a high temperature rating sufficient for your area.
Now, Florida temperatures do not require a 20w50 oil, a 10w40 carries a temp rating sufficient for Florida or Texas. However a 20w50 oil is good for that summer range, it just isn't user friendly for a colder climate in winter. Florida doesn't have cold winters, so that 20w50 is fine for Florida year round.
I will submit that a 15w40 diesel oil like Rotella T meets use specs for our bikes anywhere in the USA at the lowest cost to the user. Meets it, giving up nothing to the much more expensive motorcycle oils costing over $10 a quart.
Rotella T triple protection in the white jug at $11 a gallon at Walmart, someplace we all can find it easily and cheaply.
Or if you want an extreme temperature synthetic oil, Rotella Syn in the blue jug for $19.00 a gallon. This oil is currently being "warred" as the best oil for our bikes based on list member usage and actual use reports. So far the ones using it seem to like it for concrete reasons that they are discovering and reporting.