I recently made the switch from synthetic 5w30 to Rotella T6 5w40. I decided to do this from all the good word is has among the Jeep community. I am also running an oversized K&N high performance filter.
Prior to the oil change the engine ran perfectly fune besides a little bit of lifter tap/piston slap at startup. While driving with the Rotella the Jeep constantly drives like it is under a huge load, with a very noticeable power loss. When the pedal is to the floor on a flat road the engine will go up to 3300-3500 rpm and spudder around. I'm not sure if it is the oil or what is going on but because of the recent oil change I highly suspect the oil.
I feel that if I keep driving it like this I am significantly straining and damaging the engine.
Let me know what you think, thanks.

 

Hows your oil pressure?

 

My gauge doesn't work so I have never known it. I'd love to fix it but have no idea how.

 

no. t6 is not killing your engine.

i'm not a fan of the stuff, to be sure. I run a diesel and started using t6 around the, oh, 500 mile mark all the way to about 15k- and after two analysis's, decided it was crap compared to schaeffer's 9000 supreme, also in 5w40- which has returned stellar after stellar reports from the laboratory.

that said...

any oil made for medium duty diesels are going to have compounds meant for a different purpose than that for a gas engine. it's going to be more focussed on suspending ash- which is an issue with diesels far more than gassers- and it is going to focus more on shear strength (ability of oil to cling to parts no matter temperature/conditions) than it is concerned with washing/replacing the film between tight toloranced parts (think bearings and lifters). diesel engines are designed around this, or, oil is formulated for this...

you're better off using oil designed for your engine, not for an engine that see's temperatures far exceeding that of your 4.0, especially in the exhaust/turbo's which yours most likely lacks. your better off with an oil that is composed with products the engine needs rather than cramming all the agents diesel intended oils have in the same volume.

 

I would not put 5w( xx )oil in ANYTHING.. but then.. I live in florida..strait 40 w here

 

you realize that 5 w 40 is 40 weight oil, right? the W stands for winter... 40 weight oil is rated at operating temperature not room temperature. the W is the viscosity 'pour' of the oil before it is heated, which is to say it pours about the same as 40 does when it's hot. 0w pours even faster, and is good for winter use in cold environments. your 40 straight grade (which isn't easy to find formulated for car or liquid cooled engines) pours not similar to 5w40, but exactly like 5w40.

 

I have been a mechanic for close to 40 years now..sorry..but 5w 40 oil in hot climate is no good for older engines.. and oil pressure gauge is all i need for proof + all the oil changes I had to RE do after someone took to a Know it all garage changed oil and now the lifters rattle like crazy... but like I said.. I live in Florida.. the W for winter does not apply here..

 

do you suggest heavier or lighter if a compound oil has to be used?

 

noted.
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I've been wrenching a long time and have yet to see an engine destroyed by oil, lack of it sure, but...

 

I live here in West Palm Beach FL so I know all about the heat as well. I'm currently running straight 30W HD (loaded with ZDDP) in my 3.0L stroker. I haven't noticed anything odd in the oil pressure and I have flat tappets in mine.

 

is that of the Kendell or Amsoil flavor? both of those are fine oils, if so.. the HD 30wt is getting hard to get your hands on... the new formula is a lot less on the zddp and heavy on the phos/borine as a replacement that has a lot of potential according to lab analysis.... will be interesting to see if they stick with it or revert back... it may be the reason the HD is hard to find right now...

y'all done got me going on oil... oh dang... I better just step away whilst I can...

 

I went with the HD 30 for a few reasons, 1) It's free for me. 2) It's a modified high revving Marine engine. 3) ZDDP as I have an old style flat tappet cam and lifters.

 

flat tappet makes a HUGE difference... it is as abusive to oil as freakin' hydraulically actuated injectors (HEUI) are that mysteriously sheer 40wt to 30wt in a matter of moments and with a certainty, but won't sheer 30wt (that started life as 30wt) any at all....

the ZDDP zinc is great- but an oil that uses it in an aging and catalyst engine? not so much... it will eat a catalytic converter quickly... which is why i think they are moving to the phos/borate combo...

 

I'm just going to let the emojis speak for me on my converter situation. I live in South Florida.

 

my little smiley's and yern would say the same thing if'n they were speakin' english...