Mexstan

There has been a lot of discussion about when to switch to a synthetic oil such as Amsoil. Everybody appears to have a different idea as to how many miles should be on a new truck (diesel engine) before switching. There also appears to be some controversy as to whether to switch to a by-pass oil filter such as the Amsoil by-pass filter. I have heard everything from switching at the first oil change to only switching at 20,000 plus miles.<br>In an attempt to clarify all the issues I am asking for the 'experts' to recommend how soon a new truck can switch to Amsoil (or similar), and whether or not a by-pass filter such as the Amsoil filter will cause any warranty problems.<br>Also, after how many miles should the front and rear end be changed to synthetic?<br>After reading all the stuff about six speed transmission problems and oil types, should the factory oil be left in the transmission or should that also be switched to Amsoil? If so, after how many miles? What about the transfer case?<br>If possible, can the replies show reasons and not just opinions?

MCMLV

Yes, I would like to know also, please <br><br>Peter

Ruralmedic

No expert here, just what I know and have done. I believe Cummins recommends 20K miles for a switch to synthetic oil for the engine. I can only guess this is to insure the engine is fully broken in. By-pass filtration usually adds a couple of quarts oil capacity to the system, some will say though, that it's robs too much psi from the system. Most that use by-pass, do the extended drain intervals.<br><br>I bought my truck used. It had over 60K miles on it when I changed the differential fluids. I put synthetic in. The front was clean as a whistle, the rear had some metallic hair on the magnetic fill plug, was dirtier, but not bad. The transfer case ATF was by far the dirtiest looking when changed.<br><br>The factory fluid in the NV5600 is condsidered &quot;fill for life.&quot; I heard some running synthetic 5W-30 motor oil in it. Others have had good luck with the Red Line synthetic lube. Apparently it improves shift quality, and is backed in writing by the manufacturer for use in that transmission.<br><br>Amsoil is a small speciality oil blender. The product is good, a true PAO/ester synthetic, but expensive, and can be difficult to obtain. Being small, you will notice alot of their motor oils are not API certified, as it is expensive to do so. Also, API has lowered the anti-wear phosphorus content in the new oil specs to increase the life of emission systems such as catalytic convertors, and Amsoil disagrees with this. I can wholeheartedly recommend synthetics in the drivetrain, but it's your engine and your truck for warranty purposes. Rarely though, does the lube oil contribute to engine failure, it's usually a lack of circulating volume from some other cause. For the Cummins, it's been poor quality full flow filters, and the foil jug sealers being poured in the filter when priming it after an oil change.

Mexstan

Thanks. I am surprised that none of the Amsoil dealers have jumped on this, or anybody else for that matter. Hmmmmm. Makes me wonder ???

Dieseldude4x4

I am a dealer and I don't jump cause it just starts flame wars that go nowhere.<br>My sig says it all. PM me if you like more info.<br><br>DD4X4

P Kennedy

I agree with Dieseldude as a little common sense goes a long ways, basically if you are using a more slippery substance it only makes sense that breakin will take longer and possibly not at all. Make sure the engine is well seated before using a lubricant that drastically reduces wear in the areas that should be seated (ie;rings and cylinder surfaces). HOW MANY MILES is the question- seeing as Cummins B engines are NOT light industrial but medium duty engines the trucking industry figures on 20-30k minimum before breakin based on loaded usage miles. In the majority of our truck cases they operate at less than 1/3 of those weights regularily, I have said it before there is NO trucking company that I know of that allows paid drivers to drive around empty to break an engine in. Load them up, crank them up and go to work and their failure rate seems to be lower than DC's-go figure. PK

Mexstan

I agree totally about the method of breakin on a new engine. In the past I have always pushed an engine close to the limits. (but no lugging or cruise control for the first few thousand miles) Some of my friends have babied their engines and those are the engines that seem to give trouble. I know the CTD is more of a heavy duty engine and that is why I was checking to see what experience you guys have had with when to switch. I would rather switch early but I don't want switch so early that it causes problems.<br>So much for the engine. What about the transmission and axles? Are they as critical? Or can that switch be done early, like at say, 5000 miles?

P Kennedy

The driveline components would not bother me except leave the tranny alone as it already has &quot;the right synthetic&quot; in it. Being as far South as you are heat is your enemy and anything to help control it is good. PK

OverFueled

Mexstan F.Y.I I did the switch at 12,000. I am at 42,000. I also went to the bypass oil filters at the same time 5 microns and 1 micron of filtration. I did loose some P.S.I. 40 to 35 but I believe this is due to the lighter viscosity of the Amsoil. 5-30w H.D. 3000 It pump doesn't have to work as hard to pump. OverFueled

Mexstan

Thanks guys for your answers. As I suspected, I need to do some more driving first. I am going to be at the dealer this coming Monday and one of the questions I am going to have for him is what mileage he suggests to change at. Just for fun I am also going to ask him if I should switch to Amsoil. Hopefully the gauges I want will be available before I do the change so that I can monitor any differences in before and after oil pressures.