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Discussion Starter #1
Well gent's, I switched to a 15w40 motor oil yesterday while doing my rear diff fluid change at work. Went in early to do my Mobil-1 75w140 rear diff fluid change and decided to try the Mobil Delvac MX 15w40. We have in a 55gal drum of it at work for the older cars since it's still high ash, high zinc, high tbn, CI-4+ oil and is recommended for non roller ohc rocker arms.

Since I was due for an oil change too and it's been 100+ lately with no end in sight and no 10w30 T5 handy unless I made a wallyworld run, I decided to give it a try along with my usual 16oz of AR9100 added to the mix. So far runs great, smooth and quiet. Will see what happens when things start to cool down again, but will definitely make the switch back to T5 10w30 for winter.

Everything in this oil is perfectly suited for our engines and should be fine, it is not for 2007 and newer dpf vehicles requiring a cj4 rated oil.

http://www.mobil.com/USA-English/Lubes/PDS/NAUSENCVLMOMobil_Delvac_MX_15W-40.aspx

Harry
 

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How many miles are on the rig by now?
 

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Discussion Starter #3 (Edited)
I only have 114xxx. Ran Rotella 5w40 since new in 03' then switched last year to T5 Rotella 10w30. Back when truck was new, 1st cool weather snap with 15w40 and truck had dead pedal until warmed up.

Our trucks back then originally came with 10w30 as the factory fill. Mine flooded the crankcase with fuel at the first 1k miles from leaking injectors, they replaced 5 of the 8 and put 15w40 in. I changed to 5w40 at around 2k miles and have run thinner oils since then. It's like I'm trying corn flakes again for the first time.

Harry
 
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I prefer 15w40 in my truck my butt thinks it runs smoother. Just wish it would start in the winter I don't like switching back and forth.

100 degrees aye the polar vertex is back here they are calling for mid to upper 40's on Tuesday night. I've heard if we thought last winter was rough we are in for a real doozie here in MI this winter. It's only JULY!
 
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Discussion Starter #5
Were supposed to get a possible thunderstorm tomorrow but it still will be in the 90's, which means high probability of more fires. Already a big one in middle of state now. Weather is crazy, very unpredictable.

It looks like the Delvac MX is harder to get for the general public, we get ours from local Mobil distributor. All our overhead lines in the shop are Mobil-1 5w40 formula-M, one is diesel, one is gasoline. Both are low zinc, low ash. Our oils nowadays are for the most part all designed around emission component longevity (catalysts and DPF) and may not be suitable for some engine designs even though they claim to be backwards compatible.

Oil has definitely changed, especialy since CJ-4 was introduced.

Harry
 
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