Jeep 4.0 synthetic question

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Jul 11, 2003
I have a 96 Jeep GC with the 4.0 engine, that only has about 86k. I bought it used, but ever since I've had it, I've been using 10w-30 dino, changing every 3000 miles. Occasionally I've put in 5-30 during an especially cold period, since I park outside in the Michigan cold. Now I'm thinking about going to Mobil 1, is there any reason not to do it? I would definitely benefit from the extended change interval since I'm now living in an apartment and dont have easy access to my tools anymore. What would be recommended, 10-30 year round?
I have a '98 Cherokee 4.0 that I have been running Mobil 1 0W40 in for the past few 5000 mile oil changes. I had run Mobil 1 5W30 but it seemed to thin for the motor. I could really here the pistons rocking around when the motor was cold. (Florida cold not Michigan cold.) The 0W40 seems to work well in the Jeep. Soon I will try the Amsoil 5W30 ASL and try and stretch the OCI's out to 10-12K or 1 year rather than the 5000 mile ones I have been doing.

But to answer your question the Mobil 1 10W30 should do just fine in you Jeep.
So 5w is too thin but 0w isn't? Uh, okay.
At temps > 32F, the Mobil 1, 0w-40 IS thicker than their 5w-30 and even their 10w-30. This is due to the slope of the temp/viscosity curves for each of these oils.

Compare viscosities for the various Mobil 1 grades @ 40C and you'll see what I mean. The M1, 0w-40 is significantly thicker than the 5w-30/10w-30 at 40C.
I think the 0W40 changed every 5 to 6K would work very well for you. I found the M1 30 weights to be a little thin for the 4.0.
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