Yes, I can see a drop in oil pressure within 1,000 miles. It varies, of course, depending on ambient temperature. You tend to compare the oil pressure to what it was right after an oil change, and there is a perceptible drop with the miles.
The mega diesel engines use Babbitt bearings, however, (as far as I know) and there fore do not exert the same mechanical pressure per square inch directly on the molecules of the oil as ball or roller bearings do.
Think of the tiny point of contact of a ball bearing in the crank shaft and it's effect on the molecules of the oil that are underneath that point. That point of contact is much broader for a Babbitt bearing. You could be comparing square inches of contact in the case of the diesel engine compared to an almost infinitely small area of contact in the case of a ball bearing.
In other words, the point of contact of a ball bearing is of the same magnitude as the actual molecules of polymers in the oil, so the polymers are literally crushed. Mechanically damaged.
Besides, its not the size of the engine. Those huge diesels have a huge oil sump capacity so their effect on the oil is no greater than our tiny 650 cc with only 2 quarts of oil in the sump.
And, except for synthetics, all of these oils are based on the same technology of using polymers for viscosity enhancement and making a multi viscosity oil. I don't think that the polymers in diesel oil are any better than the polymers in auto or motorcycle oil.
Last Edit: Apr 1, 2010 5:59:28 GMT -5 by pamcopete
I can't get more than 1500 miles before bike starts smoking, thats when I do oil change It's shear from gears that does most 'damage' to polymers, the point contact of bearings does some 'damage' but no bearing in XS engine is really spinning very fast/ Plain bearing cranks 'don't have metal to metal contact, unless something goes very wrong they 'float' on an oil film. The Royal Purple guy was trying to sell the stuff, it does sound interesting how it's made though, they 'build' oil molecule at a time.
There are three types of people in the world, those who can count and those who can't I dabble in rocket science, when I'm not picking my nose
I would attribute your "luck" more to the frequency of the changes than to the brand, Pete. I believe that you have made that point in some othe threads. Frequency of oil change is the most important factor.
As to break-down of the molecules, I'd always heard that it was the transmission in "unit construction" power plants that chewed up the oil.
If you have a "contact patch" anywhere in the motor you got problems.
There has got to be some reason why the high-compression motors get more ZDDP in their formula.
Intuitively it seems having a good ZDDP shield should signficantly reduce the effect of the deterioration of the oil. Thus, oils with plenty of ZDDP should remain servicable longer.
Everything I read here reinforces my opinon that while there are several ways to go, Rotella 15-40 is certainly one of them. Using the old formula Pennz @ 1000 miles as a proven base-point. I conclude that while hard service may call for more ZDDP, for daily driving Rotella 15-40 changed at 1,000 mi is right smack dab on da money.
You are looking at less than 5 bucks an oil change and getting the same or better ZDDP level as the old Pennz.
Yes, frequent oil changes will hide a lot of sins. I got 360,000 miles out of my '86 Vette and never had any engine work done. Didn't burn any oil, good compression, clean plugs. I used Pennzoil and changed the oil every 3 to 5,ooo miles.
I also got 80,000 miles out of my '78/E without ever tearing down the engine, although I did change the valve stem seals without removing the engine from the frame or taking the head off.
Not sure what you mean by: "If you have a "contact patch" anywhere in the motor you got problems."
The need for more ZDDP in high compression engines I think has to do with the fact that everything in the engine is tighter and stronger, including the valve springs, and if the valves are using old style flat tappets the more ZDDP is needed.
crazypj...I don't think it is necessarily the RPMs of the engine, but just the pressure of the piston con rod bearings and crank shaft bearings on the power downstroke pressing on a very small point of contact between the ball or roller bearing and the bearing race.
The Pennzoil Motorcycle oil must be basically what I started out with (SH) rating because it is rated for that service category, so they probably didn't change much to call it a "Motorcycle Oil" which reinforces my claim over the years that Pennzoil auto oil with the SH rating was great.
So, I think in switching to Pennzoil Motorcycle oil, I am basically continuing on with the same oil.
What confuses me is why they changed the 20W50 auto oil to an SM rating and reduced the ZDDP to protect catalytic converters. 20W50 oil is probably used only in older vehicles, tractors and motorcycles that do not have a catalytic converter.
Last Edit: Mar 28, 2010 14:32:40 GMT -5 by pamcopete
Is anyone using the Castrol Diesel oil? It's a 15W-40 with these ratings: Applicable for 4 stroke trucks, gasoline and diesel light trucks and passenger cars where API CI-4, CH-4, CG-4, CF-4, CF SL or SL SJ are recommended. It is suppose to have a high ZDDP rating but I haven't been able to determine the value as of yet.
retiredgman, thanks for the info. I used it all last season and didn't have any issues with it. However, after reading this discussion and several others I saw little to no info on the Castrol Diesel so I wanted to get an opinion.
I have also written to Castrol asking for ZDDP ppm information. I will post it if they write back.
Just in from Castrol Oil: Not encouraging
Although Castrol Diesel oils carry an S rating, its primary credentials are diesel. The S rating is meant for short term use if the owner cannot find the appropriate gasoline engine oil. Diesel engines and gasoline engines have different operating regimes (loads, temperatures, speeds, fuel, exhaust recirculation); the lubricants are formulated differently (additives, ZDDP) to be in line with the primary operating requirements of the engine. Diesel engine oil is formulated with very high levels of detergency to counteract the soot that is circulated back into the oil. Detergency is surface active and does compete with ZDDP for the surface of the cam lobe and lifter face. The proper engine oil to use long-term in gasoline classic car engines is an oil designed for use in a gasoline engine with the correct level of ZDDP to protect his cam and lifters.
Product Recommendations for Flat Tappet (Solid Lifter) Cam Engines:
Castrol Syntec SAE 20w-50 (Recent reformulation identified by "Recommended for Classic Cars" text on back label) (min Zn = 0.12 = 1200 ppm)(full synthetic)
I am thinking of changing from Pennzoil to Pennzoil motorcycle 20-50 if only I could find it. I went in 3 different bike shops today and none had the Pennzoil. All the new bikes must use some variety of synthetic because it seemed that was most of what they carried. I wish they would come up with a good oil for these old bikes and leave it alone whether it was a diesel oil or motorcycle oil. In this climate I worry about oil. Jeffery
r80rt: :)This is a splendid write up, THANK YOU!!!!
Dec 26, 2015 16:54:05 GMT -5
mashermoto: What the what is this shoutbox for? Or should I shout, WHAT THE WHAT IS THIS SHOUTBOX FOR!
May 12, 2016 22:22:21 GMT -5
motormike: Good Day ...just a FYI.. Wild Cat is this Labor Day weekend. Still go'n on. A few 650's still make the scene. Various rides at different skill levels each day.. awards dinner sunday eve. BS in the park'n lot after dinner.
Aug 23, 2016 7:57:01 GMT -5
lsettle: First post in over 6 years!
Aug 28, 2016 19:45:17 GMT -5
kardon: Wow quiet here, where did they all go.
Oct 7, 2016 2:18:13 GMT -5
gggGary: XS650.com LOL
Feb 16, 2017 20:49:02 GMT -5
buell88: Anybody have any idea who built the xs650 tracker used in the Draggin Jeans Ad on Pipeburn?
May 16, 2017 16:24:09 GMT -5
joshua: The regulator/rectifier unit I got from Mikes PMA has closer hole spacing than original. Are we supposed to mill the holes to fit?
Jun 7, 2017 19:25:58 GMT -5
joshua: My bad. I found the bracket they supplied to mount the rectifier/regulator... Uh oh. How is this meant to work? Which way is it meant to mount? Looks like I have to use some spacers or something. Good instructions would be nice.
Jun 7, 2017 22:09:52 GMT -5
craig8johnson: Not sure if this is the right spot or not but oh well...
Jul 11, 2017 18:04:15 GMT -5
craig8johnson: I'm checking the charging system. I'm afraid I might have fried the last battery. With the solid state regulator (after market) what should it be charging at. The book says, I think, 15 volts. I'm hitting 17 when revved. Is that too high?
Jul 11, 2017 18:06:19 GMT -5
gggGary: Yes 17 volts is too high, about 14 volts is max, sounds like you don't have the right regulator or it's wired wrong.
Jul 13, 2017 6:54:33 GMT -5
dean: Just saying Hello, new member who is going to fix up a 79 XS650 that has seen its better days. I will definitely have lots of questions coming up.
Jun 23, 2018 16:45:32 GMT -5
tt650: Trying to breathe life into a 1980 that's been stored (indoors) for 25 yrs. Air filters are dry rotted. Have cleaned carbs but she only runs briefly on choke then stops. Need jet setting info and other ideas that might help her idle and rev.
Jul 3, 2018 19:15:19 GMT -5
trix13: Hey everyone! New to the forum and am fighting those gremlins!! New charging system, ignition switch, coil and fuse box. Resistance is higher than normal on the ignition pick up so I'm trying to find one. No such luck yet.
Aug 16, 2018 8:50:48 GMT -5
trix13: Also, even though all of my connections are clean, I cannot seem to find out why , when at higher rpms, I hit the signals and the rpms pulse with the signals...hahah. same with the brake light. I appreciate all input!!
Aug 16, 2018 8:55:08 GMT -5
bob99: how do I post a question. I am new to the forum
Jun 6, 2019 10:52:10 GMT -5
adlpc: Hello all! Been enjoying your edifying posts and discussions - and as a fan of the XS650 since my early teenage years happy that I now own a 1980 Special which I plan to turn into a vintage half faired racer. Thank you all for being here!
Oct 1, 2019 0:58:56 GMT -5
jimothyj: Hello everyone, I just joined & wish would have known about this site in 2014 when I brought my 1974 TX650A back from the grave. I have spent a good deal of $$ and alot of time on it. Just painted it and working on electrical, I will post pics soon,
Apr 10, 2021 2:14:13 GMT -5
louisvan: trix13 - I had a problem with my 1975 SX650. When I got to highway speeds, the engine lost power. The problem was in the connectors. At a certain vibration and the wind pushing on the wiring loom, the connector lost continuity. A bad crimp to the wire.
May 20, 2021 1:19:09 GMT -5