Accidental use of synthetic oil

Last oil change I took the offer of a friend who recently sold his powerstroke and bought his overstock of Amsoil off of him for dirt cheap and changed my oil like usual. Long story short I didn't realize it was a synthetic. We've always run Rotella in our trucks without issue and I'd like to keep it that way with Motorcraft filters. My question is this; at 95k miles on the truck and having recently only done the last oil change at about 5k miles ago with the Amsoil synthetic (just this once) can I still switch back to basic Shell Rotella still or is it too late? I don't mind paying a little more but it looks like synthetic oil is almost twice as much for the Shell Rotella synthetic. Any help on this I'd appreciate it

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You can switch back and forth all day long safely but I use nothing but synthetic in every truck, car, tractor, lawnmower I own, I like the looks of it every time I change it and IMO you can't beat it for high heat and cold temps..

Yeah doesn't matter, feel free to switch back

Atsah said:

You can switch back and forth all day long safely but I use nothing but synthetic in every truck, car, tractor, lawnmower I own, I like the looks of it every time I change it and IMO you can't beat it for high heat and cold temps..

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OK well I guess I will stick with it then thanks man. It just costs sooo much more lol

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One of those things you get what you pay for

NCSU dirt man said:

OK well I guess I will stick with it then thanks man. It just costs sooo much more lol

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If I plan on keeping something for a long time I use nothing but synthetic.. The synthetic doesn't need to be changed as often as conventional oil so it doesn't cost that much more really.. You are driving a 50-60 thousand dollar truck aren't you? LOL

Mine cost like 10000$ lmao

Only time i remember synthetic being a big deal was with cork gaskets on older OTR trucks and farm equipment. Used synthetic once on a '50's Farmall and she leaked like a sieve when we tried using regular oil again, just had to replace the old gaskets.

But to my knowledge cork hasn't been used in gaskets for half a century, but I believe that's where the "is it safe to switch" issue came from. I could be wrong as the night is young but the beer is half gone so... yeah...

Ya the older stuff would run on anything and the cork with synthetics was a nightmare..

Thanks everybody for the input

Atsah said:

If I plan on keeping something for a long time I use nothing but synthetic.. The synthetic doesn't need to be changed as often as conventional oil so it doesn't cost that much more really.. You are driving a 50-60 thousand dollar truck aren't you? LOL

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Well that being said what is the safe oil change interval with a synthetic then? I mean we participate in CAT's SOS program on all of our tractors, dozers, excavators, graders and pans. But truthfully we've never even considered it with just our basic 3/4 and 1 ton fleet trucks or on the Peterbilt and Macs we run as our lowboy and dump trucks. I have always changed my own truck's oil at about 4500-5500 miles period. How much longer am I looking to go with a synthetic oil between changes? I have read a lot of people claiming these 6.7's have blow-by but then again my truck rarely idles much either as I am usually commuting from office to site or home. Not a big fan of idling period

I go 7500 on Mobil 1 5W40 year round. I really don't know a lot about the 6.7's but If I had one I would go the 7500 between changes.. The older trucks, (6.0's) I have owned destroyed the oil within 5K no matter what oil I used..

On the other hand, if I was planning on keeping a truck for 140-150K I probably wouldn't bother spending the extra money on the synthetic's..

cool thanks man!

If you have a CCV mod, you'll lose a quart every 5k miles due to blow-by.

Notneb said:

If you have a CCV mod, you'll lose a quart every 5k miles due to blow-by.

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not yet unfortunately. will do that one down the road though to accompany the other "mods" haha

Atsah said:

If I plan on keeping something for a long time I use nothing but synthetic.. The synthetic doesn't need to be changed as often as conventional oil so it doesn't cost that much more really.. You are driving a 50-60 thousand dollar truck aren't you? LOL

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Didn't know synthetic was more resistant to contamination.

Billy T.
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Oils with poor shear stability will 'shear out' and lose viscosity. Synthetic oils have far superior shear stability compared to conventional oils and Diesel oils tend to have higher levels of detergents in them..

I'm no expert in motor oils but I do know synthetic's stay more in tact over longer periods of time than conventional oils do..

Here watch this video from Rotella

https://youtu.be/MEaf5ES6Xmg

That 15-40 looks like glue...

Pretty much

OK so long story short just run a Rotella synthetic or a synthetic blend for my truck that typically operates in the NC climate of anywhere from 20 degrees in the winter up to 105 degrees & very humid in the summer and I will be fine correct? I mean the oil is gonna get changed regularly I'm not looking to push this truck to unreasonable expectations lol. 5W-40 Rotella synthetic is OK in a 6.7 powerstroke right? I saw motorcraft had a different weight (can't remember what it was now though)

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