Has anyone ever used the Amsoil system in their cummins 5.9? Had a sales rep guy sing its praises at a recent campout but I never met anyone who actually used it.

Stick with known products - Shell Rotella T or Mobil Delvac. I've examined Amsoil's claims on product "qualifications", and they're evasive. Both MWrench and I have had negative experiences with Amsoil in the differentials.

Frankly, I doubt your campground friend has the credentials or experience to have any credibility.

Thanks for the warning,Rusty.

I certainly agree with Rusty's comments. I would also add Kendall semi-synthetic. I have used all diesel oils and have found that Kendall will maintain a higher oil pressure (5-7 lbs) under all operating conditions.

I used to see 50 lbs but after switching to Kendall, I now see 55 lbs.

My 5.9L Cummins will drop 5 lbs oil pressure if the water temp goes up to 200 +/-degrees.

Kendall is a bit more money but I have extended my oil change interval to 10K miles. I currently use about a quart per 3K miles, not bad for 240K miles.

I agree - I used Kendall DIII in my Nissan Maxima diesel - put 250K on it; sold it to my sister, who put another 400K. Still running at 750K; nothing internal ever touched.

Amsoil has a great loyal following among the 2 stroke snowmobile racer crowd, those oils have been highly touted for years. OTOH, none of their other products are regarded that highly.

As Rusty said, Amsoil has been stubbornly avoiding many of the standard laboratory tests, using anecdotal testimonials, etc. I have heard little about their engine oils, but their gear oils are not the best. I also am leery of their products for these reasons.

Regarding the Kendall, can you suggest what weight to run in my 5.9 Cummins. I will be operating in temps. above 32 degrees F.. Also, I will at most put 2K miles per year. Need I replace the oil yearly? Thanks for your thoughts.

The manufacturer's recommendations should be followed with regards to viscosity; any reputable brand will otherwise be qualified.

Most all diesel lubricating oils for use year round is 15W-40. this should be good as long as you are not running in really cold climates such as Alaska.

Change intervals would depend on how you operate the engine and the climate you are operating it in.

If it is cold and you only run short runs you will build condensation that will accumulate as it take time at operating temperature to evaporate the water. Diesel engines run a bit cooler oil than gas engines.

Storage is a another consideration. NEVER run an engine for short periods of time during a storage period. If you are concerned take it out for a drive of at least 20 minutes at full operating temperatures.

With only 2K miles per year and proper storage, I wouldn't be to concerned about annual changes, probably every 2 years would be fine

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Storage is a another consideration. NEVER run an engine for short periods of time during a storage period. If you are concerned take it out for a drive of at least 20 minutes at full operating temperatures.

I run mine 15 miles every 4 weeks when not otherwise on the road.

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With only 2K miles per year and proper storage, I wouldn't be to concerned about annual changes, probably every 2 years would be fine

"Oil's cheaper than metal"...(I heard somewhere). 2K/year is the classic definition of an "Aunt Minnie" - short hauls. I'd change the oil annually, but reuse the filter - better yet, put more miles on it.

15/50 it is. I noticed I can get Rotella T cheap in that weight. And it appears in most all Barth forum discussions that it is highly regarded. Thanks MWrench and Rusty from all of us who recognize the part you've played in keeping these old girls rolling.