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Discussion Starter #1
so i was wondering, is it safe to go to synthetic in the winter then back to 15w-40 in the summer? ive always been told that in a gasser once you go synthetic you shouldnt go back. assuming thats true, is it the same with a diesel? just looking for a lighter weight winter oil. if not ill jsut use the 10w-30.
 

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so i was wondering, is it safe to go to synthetic in the winter then back to 15w-40 in the summer? ive always been told that in a gasser once you go synthetic you shouldnt go back. assuming thats true, is it the same with a diesel? just looking for a lighter weight winter oil. if not ill jsut use the 10w-30.
That is one of those auto rumors that just won't go away. You can go back and forth from conventional to synthetic at any time. I have gone back and forth at least a dozen times with NO adverse effects over the course of 400k miles with at least 5-6 different vehicles, gas and diesel. No issues...ever.

I plan to run Rotella T5 10w-30 synthetic blend in the winter and whatever 15w-40 is on sale at Wally World in the summer.
 

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Discussion Starter #3
thats kinda what i wondered. i never run synthetic in our car, so never bothered to check the facts. thanks for the info! the 10w-30 is much cheaper than the synthetic anyway.
 

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thats kinda what i wondered. i never run synthetic in our car, so never bothered to check the facts. thanks for the info! the 10w-30 is much cheaper than the synthetic anyway.
If I could get MC 10w-30 for a good price I would run it but the stuff is 5 something a quart at the local shop by me. Even Rotella 10w-30 conventional is 18 bucks a gallon at AAP, Wally World has T5 at 16 a gallon. I might check out JD Plus 50 10w-30 see if that is any cheaper than the Rotella. I doubt it is but might as well check.
 

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Discussion Starter #5
let me know what you find, i though 10w-30 price was pretty close to the 15w-40. but i could be wrong.
 

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That is one of those auto rumors that just won't go away. You can go back and forth from conventional to synthetic at any time. I have gone back and forth at least a dozen times with NO adverse effects over the course of 400k miles with at least 5-6 different vehicles, gas and diesel. No issues...ever.

I plan to run Rotella T5 10w-30 synthetic blend in the winter and whatever 15w-40 is on sale at Wally World in the summer.
thats good info cause i wanted to try a synthetic in my truck, but was afraid that if i didnt notice a difference i couldnt switch back.:thumb:
 

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let me know what you find, i though 10w-30 price was pretty close to the 15w-40. but i could be wrong.
Yeah, I might give a dealership a ring and see how much the MC oil is there but at the shop by me, which is actually a heavy and medium duty shop that services powerstrokes, has it for 5.18ish a quart...crazy. Rotella T6 is cheaper than that.

T5 10w-30 for 4 bucks a quart is a pretty slamming deal for a oil that has cold flow properties (the only reason I want a synthetic or blend) that is pretty close to T6.

thats good info cause i wanted to try a synthetic in my truck, but was afraid that if i didnt notice a difference i couldnt switch back.:thumb:
No problem, I have never had an issue going back and forth. I know way back in the people claimed to have issues but nothing made in the past 20 years should have issues with it.
 

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We have a farm/ranch store here that sells Rotella T6 15-40 for 12.99 a gallon all the time. Might see if you have a local Tractor Supply or Attwoods, or Orshelins near you.
 

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WalMart has the Rotella 15W-40 for $12.49 a gal right now by us. Just picked up 8 gallons.
As for switching back and forth I agree internet myth. Also the modern DINO oils are far superior to the synthetics of just ten years ago. Blackstone proves this, if you are in the colder climates switching to a lighter weight oil for Winter is common and it helps a great deal.
 

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Discussion Starter #11
makes sense. iirc, it had to do with seals and gaskets or something. use synthetic and they are lubed and kept fresh, switch back and they can dry out and crack or something. either way, im sure it was probably and old school truth or something. and as stated, materials have improved. thanks guys! good discussion.
 

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Conventional oils have come light years since the days of straight 30 weight oil and really unless you are running super long OCIs there really isn't much of an advantage running synthetics in most cases, especially when you factor in the cost of synthetic oil.
 

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Discussion Starter #13
personally, even with a synthetic oil, i wouldnt run much longer without an oil bypass filter.
 

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Oh the oil myths! They always make me chuckle.
 

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I need my oil changed, im running rotella 15-40. I was woundering if the synthetic would be better for my truck? I live in louisiana and we get real hot down here. What would you guys recommend? last oil change was $85.
 

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I need my oil changed, im running rotella 15-40. I was woundering if the synthetic would be better for my truck? I live in louisiana and we get real hot down here. What would you guys recommend? last oil change was $85.
If you changed it yourself with Rotella T6, you would get synthetic oil for abotu the same money!
 

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what is the lightest weight conventional oil (non synthetic) that is safe to run in my truck. I run rotella 15-40 now and thinking about thinner oil for the winter but dont wanna drop big $$ on synthetic.
 
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