Had the truck since January, been using Valvoline 15w-40 dino since, and the oil pan leaks and leaves a couple drops in the driveway everyday, no big deal. Did an oil change in prep for cold weather last week, used Rotella 5w-40 synthetic, and now she leaves puddles. Once winter sets in I plug the truck in at night anyways, so should I switch back to dino or wait it out till I replace the oil pan gasket (unkown date)...I'm dreading pulling the motor mounts and what not.

That's the problem with syn, if you have any leak, it will be 10 times as bad. I only run dyno oil because I see no need to syn unless you are doing extended oil changes.

If oil leaks out dirt is being pulled back in during heating cooling cycles. don't put off fixing leaks too long. The myth of synthetics causing leaks is just that..a myth, as far as making an existing one bad possible but I keep even my smallest leaks fixed so I don't let them get bad enough to find out but I also switch everything to synthetic as soon as I buy it. I don't like spending all the extra money long term nor dealing with issues from dino oils.There is a reason that you find almost all OEMs come from the factory with a semi or full synthetics the last few years. Heck there are companies like VW that have used synthetics for 10+ years and will void your warranty if they detect an engine failure due to use of dino oil.

Not sure what kind of temps you see but I've never had any problems with 15w40 year around. Even my brother in law in Wyoming runs it year around, and I've seen his truck sit for days on end up at their cabin at 10k feet in sub zero weather (No electricity, so no block heater). Synthetics give an advantage with cold starts to begin with over dino oils.Did you try snugging the oil pan up a touch? I would use caution but it may be worth a shot, at least to eliminate the possibility of a loose bolt or 2.JR

I've never had a reason for synthetic oils for the truck being more people have crossed the million mile mark on petroleum oils. To this day I never found anyone that cross million milestone with synthetics. I use 15w-40 Mobil petroleum oils all winter long with absolutely zero issues. (Minus weather too)

What most likely is happening is the syn is breaking away the buildup that has kept your seals from leaking, they say there is additives in syn that are suppose to lubricate and swell the seals but it could take a year. I have seen it happen many times by switching over and like said before, I see no use or advantage in running syn. I ran it once in my wife 4.7 grand Cherokee just to see what it would do and I saw no mileage increase and actually smelled oil burning the 6K miles it was in there. Once I switch back to dino oil, I haven't smelled oil once. I run 15/40 year round in western Nebraska. If you have to change out the oil pan, you just have to take all the bolts out, then reach up in an unbolt the sump. Then the pan will pull right out without doing anything with the motor mounts. I would try tightening the bolts on the pan, also look at your crankcase vent bottle and vacuum pump for leaks.

I've never had a reason for synthetic oils for the truck being more people have crossed the million mile mark on petroleum oils. To this day I never found anyone that cross million milestone with synthetics. I use 15w-40 Mobil petroleum oils all winter long with absolutely zero issues. (Minus weather too)

Look at the amsoil website and read the articles, stories of folks running a million miles plus several times a year and surpisingly a lot of them are gassers as well. Don't think what you read on forums is all the world has to offer, might see a fraction of one percent of the total number of folks who actually hit a million miles listed on forums like this, I know of a half dozen just in the single small town of Bismarck that have broke a million miles running synthetic. The only way it doesn't pay off is if one is still living the old school wasteful ways. And as for replacing a pan gasket, unless you have 6 year old sized hands and arms, I have always had to loosen the motor mounts and lift the engine a couple inches at least so the bolts are to the top of the mount slots to get in to remove the sump piping from the pump to get the pan off. This is on 4X4's, I have never done one on a 2wd rig, they are extremely scarce here in ND.

When my truck was new my pan leaked. Not trusting the dealer I went under there and gave each bolt a nice hand snug tight. Not wrenched but snug and it has never leaked since.

This is why I love this forum! It's always a learning experience. Thanks a lot guys and Michael!

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Next question, cummins gasket or rtv? Any long-term successes?

Well, after many frustrating hours and a bent engine hoist extension, replaced the gasket with a fel-pro 1 piece paper gasket, NO RTV. Got her up to operating temperature and no leaks. We'll see how she does after a 40 minute commute tomorrow...