I'm curious myself. I have heard of oils adding hp, but I have not heard of it lowering RPMs. However, if such a claim were to come from a certain oil, I would expect it to come from an Amsoil user or Amsoil as it's users claim some extraordinary things, some I believe and others I don't. Does Royal Purple make any oil for a diesel engine? I have seen this oil on auto shows adding some good HP to sports cars when the existing fluids are replaced by it.

 

how good is the SYN. Rotella T 5 - 40... I see they sell it at Walmart for a good $$$.. Was thinking about AMSOIL - BUt how does RoTella Syn. compare???

 

Thats what I'm switching to after break-in. It is probably as good as any other oil and will certainly get the job done. I would bet that you could not tell the difference. I too like the price and the ease of getting it compared to Amsoil.

 

coolslice -

any idea how long its good for.. not that I am going to the for ever thing... do something like 10,000 miles and change filter at 5,000 ???

 

Ok for you naysayers. Common sense is somthing that you are NOT using when you say how can an oil cause you to loose 200 rpms. Let's see simple science here, if you have better lubrication, ie a better oil, then it would make since that the engine does not have to work as hard to acheive the same speed. So in other words the rpms would in fact be less at a given speed.
NO I did not change gears I just changed the oil to a top grade synthetic oil. Prior to installing synth oil take your truck out on some flat area and set the cruz at about 65mph and observe the rpms. Then after you change the oil take the truck to the same area and ensure it is loaded approximatley the same and repeat the same thing. If the engine has been properly maintained and is clean, you may have to change theoil 2X to get it nice and clean after running dino oil, you should see a difference in rpms for that speed.
I have seen this reduction on various vehicles that I have owned and have also seen the benifit of o top grade synthetic oil in the winter time as to the starting capabilty of the engine. Lower pour point of the oil and better lubrication alows the engine to start much easier.
OK I'll get off my soap box and let you boys & gals fight about this supject soem more.

 

Ckennedy and Coolslice - the rotella 'synthetic' is a group 3 based oil, which means it's partly dino oil in its makeup. Sometimes walmart has it for $12.80 or so, and periodically they jack it up to $16.50 . For $12 it's not a bad deal, however for about $15/gal you can get Amsoil heavy duty diesel/marine 15w40, which is a fully synthetic based, much better performing oil. Plus it's mailed to your door, doesn't get much easier than that.

 

I'd say you are fine w/ those figures. A few will disagree with me on this, and I'm not saying this is the right thing to do at all, and I don't do it. I used to work for FedEx, all of the trucks had the 5.9 Cummins in them. These trucks went through hell. In town, dusty gravel roads, you name it. These trucks were never warmed up, cooled down, or driven anywhere without full throttle take offs, and constant turning off and restarting. You get the picture... These trucks got on oil/ filter change about every 20k miles. The filters were Napa's cheapest filter and the oil was so cheap it didn't even have a name that I can remember . This seemed to work just fine as most of the trucks were over 200k and some over 300k. There were NEVER any internal engine failures, just fuel/ lift pumps and fuel lines. I kinda feel like people go overboard on the oil thing sometimes, people can argue with me, but I have seen first hand what these engines can take many times over. This is why I bought one. 99.9% of people with these trucks will sell them waaaayy before they reach the end of their service life, I know I will, so the whole bypass system, true synt, oil analysis things isn't worth it to me. This engine will last longer than me even with poor maintanance.

 

SuperGewel
You are mistaken.
The engine and the wheels are tied together when the lock up clutch in the Auto trans or if in the case of a standard transmission when the clutch is engaged . and changing the oil is not going to change the rpm one bit if the ground speed remains the same regardless of what kind on oil is used. I will agree that it may use less fuel with a synthetic but unless the clutch is slipping the rpm is going to be the same.
Jim O

 

where can you get the Amsoil for 15.00 / gallon? It is 21.00 gallon on their site.

 

i had the same question

 

"Common sense is somthing that you are NOT using when you say how can an oil cause you to loose 200 rpms."

Wow!

65mph X 3.73 X .69 X 336 / 30.5"= 1843rpm
65mph X 4.10 X .69 X 336 / 30.5"= 2025rpm

This is the rpm of an automatic in O/D with stock 30.5" loaded tires...
Regardless which brand type or color of oil is in the crankcase. Synthetics might give some imeasureable increase in mpg but it won't change engine rpm. Sorry.