Bullamakanka said:

And quite humorous!

I have also heard to run conventional oil the first 500 miles after a rebuild because synthetic oil is too " slippery" and won't seat the rings properly.  When I bought my new car (honda) they said the same thing- first oil change @ 3000 refill with conventional, then you can go with synthetic after 6,000 mi.  BTW my Civic owner's manual recommends 10,000 mi intervals on oil change w/ synthetic, and 5,000 mi intervals with conventional.

Have kept the conventional oil in so far, have 2 litres left over so will use that then switch to synthetic.

Quote

Wives tale; use synthetic from the start.  What do you think they put in brand new high performance engines that are sold around the world?  SYNTHETIC.

Actually in ALL engines sold around the world...

Read this article for break in:

http://www.mototuneu..._in_secrets.htm

CHIEFCULPRIT said:

Exactly what I used, mix of street and track(being a 5km dirt circuit)

As a 7.3 powerstroke owner this is what I really like to hear

Baja trail Rider, on 21 September 2011 - 07:38 PM, said:

Interesting.  I drained out Rotella 15-40 yesterday and it was black.  Back to synthetic.
I talked to an XR250 owner that had his cam and rockers ruined using car oil.   Megacycle cams told him to use Redline.   Also, two riders that sucked the choke plate into XR motors.   One 250 and one 400.  Amazingly, they pulled out the choke plates and not parts needed replacing.  The choke plate was removed from the 250 by blowing it out the exhaust!

I just picked up 4 quarts of Mobil 1  15-50.   $6 at OBriens Auto.   About the same price as  Rotella dino oil.   I noticed Mobil 15-50 states "Has Zinc for high performance engines."   There was no motorcycle oil at the store, so I could not compare costs or labels.  I just switched my CB750 from Mobil 1 15-50 to Rotella 15-40.   It is shifting really smoothly and usually, I have it going fast on the freeway, so I'll still with Rotella in it.

Edited by Kev_XR, 01 July 2012 - 02:38 PM.

I use Mobil 1 15w50 in the dirt bikes and in the hotrod.  (mustang)
Good Stuff!

In our "gang" we have 4 XR400s, I'm using Motul full-synth, the others good quality Motul semi-synth.

There is no question the full-synth is better, runs more silent and cooler, with better clutch and tranny. We all change after ~1000kms, the full-synth is still far from black, the semi-synths are deep black - you can also feel on your finger the full-synth is holding up well. No difference in oil loss.

And they cost almost the same. But I just can't persuade these guys that full-synth is fine for our old low-tech XR tractors...

I've found big difference between oils on how the clutch works, and how long until tranny shifting becomes notchy, etc.  Anecdotal experiences from other such as Baja Rider will help you pick a oil suitable for your use. I've found Honda HP4 oil lacking and have found better results using Rotelo oils.

The best source for info on oil  is the oil's spec sheet, most are available online.  It will show viscosity at 40C and 100C, plus High Temp High Shear (HTHS) measured at 150C, along with other specs. The later two are very important for an air cooled engine which is a strong point of syn oils, they provide high temp stability with low viscosity at  40C.
The car oils have relatively low HTHS thru the 10W-40 weights  with a big jump for 15W-40 and thicker oils.  The exception is some of the syns such as Mobil 0W-40 have good HTHS, but each oil needs to be researched.  IMO the oil for a XR should have a 100C viscosity greater than 13 and HTHS greater than 3.5.  Here is data on a few oils:
....................................Bottle.......... Vis.......... Vis......... HTHS
................................. Label......... @ 40C.....@100C....  @150C
Rotella T6 Syn........ 5W-40............. 87......... 15.02......... >3.5
Rotella T................. 15W-40......... 118.......... 15.7........... >3.5
Torco Blend............ 20W-50......... 173.......... 20.32........ >3.5
Castrol GTX........... 10W-30........... 75........... 11.3............ 2.9
Mobil-1 Syn.............. 0W-40**... .... 75........... 13.5.......... >3.5
Castrol Syntec*........ 0W-30**....... 125........... 14............. >3.5
Mobil-1 High Mile.... 10W-40........... 69........... 11.7.......... >3.5

ramz, on 29 September 2011 - 06:52 PM, said:

I agree that's true of high performance engines.  Last I checked the XR's single cylinder tractor engine didn't have a whole lot in common with those.  There's a gazillion experts that suggest running dino oil for break-in on older engine designs.  Besides, its cheaper and you're just going to change it right after break-in anyway so why not save a few bucks?  If you want to compare our engines to a 4-wheeled counterpart when it comes to engine design then I would look at something like an old aircooled VW 1600 rather than any of the modern cars today.  Plenty of data and expert advice for those engines available - one might even say cult-like.

To the OP:  Syn will give smoother shifting and more mileage between needing a change but the best thing you can do is to frequently change the oil.  I'd definitely run synthetic if I was doing a long, high speed, multi-day ride in harsh conditions.

Kev_XR, on 01 July 2012 - 09:49 AM, said:

You say that like it's a bad thing.  Black means its working.  Diesel oil is packed full of detergents, and is formulated to do an excellent job at suspending debris and contaminants (ever see how black diesel oil turns after an hour in a diesel?).  Obviously, your engine was dirty and the oil was doing its job and cleaning it out and suspending the junk.  I'd stick with it if I were you, at least until it holds its color like the lesser oils.

JayC

jayc250x, on 02 July 2012 - 12:09 PM, said:

Oil also breaks down with heat.  Chances are, it was suspending it's own trash.  

Synthetic oil stands up to heat FAR better than conventional.  Air cooled engines that are ran hard are PRIME candidates for synthetic motor oil...  as they run hotter than water cooled engines.

n2omike, on 02 July 2012 - 01:38 PM, said:

Not sure if that was part of a reply to my earlier post or not.  I'm not saying that synthetic isn't good in air cooled engines - far from it.  Just that during break-in you should still stick with dino oil on these engines.

wallrat, on 02 July 2012 - 03:47 PM, said:

I agree.   Breakin method is very dependent on bore material, bore prep, and ring material so If the manufacturer put in dino oil then continue to use it during breakin. On a rebuild follow the ring manufacture recommendations.

I was advised by a performance engine builder in Las Vegas that running full synthetic oil will prevent new rings, valves and cams from properly seating or wearing in. Full synthetic oil will with stand higher temps before breaking down providing better lubrication and preventing engine wear.

Edited by Vegasdirtrider, 09 July 2012 - 10:19 PM.

n2omike, on 02 July 2012 - 01:38 PM, said:

I am pretty sure I had under 600 miles since the previous oil change.  Either way, Mobil 1 15-30 was on sale for $6 a quart, which made it almost as cheap as Rotella 15-40.   Filled up the XR400 and have enough stocked up for another 3 oil changes.