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It’s ok that we don’t all agree on everything. The world would get boring.
The OCI for conventional oil will be 5000 miles.
The OCI for synthetic is 7500 miles or more.
My UOA’s showed the same amount of wear with conventional oil at 5k as synthetic at 7.5k. Zero ‘improvement’, just more miles for synthetic before it breaks down.
I can get STP 15w40 conventional oil for $9-10/gal (comparable to Rotella and TSC brands). The wear is NOT reduced by spending more per oil change on synthetic oil and the math doesn’t add up to a savings because of increased OCI. Picking on my friends - it makes ZERO sense to do a 5k mile OCI with synthetic oil. Y’all do a couple of UOA’s out to 7500 or more miles and compare wear. In my case, the wear was the SAME at 7500 miles. That was at 22-24k lbs gross towing cross country constantly.
I agree, the lower viscosity oil definitely makes a difference in how SMOOTH the truck runs after a cooooold start, but all of that clanging and banging doesn’t hurt anything.
I've said it many times, oil is oil as long as you change it regularly (5k in my case on these old engines), and as long as you don't reach the max temp braking point of the oil you should be good.
Change it often and your engine will last forever.
Now if you want to extend your OCI, then by all means go to synthetic but for it to be worthwhile IMO oil has to be good for at least 15k+ miles in an OCI to be worth going synthetic in my junk which by reading old UOA it seem the 7.3 doesn't play nice with extended OCI's.
Sous good on you! You are doing great service for the Brotherhood of 7.3L PSD owners. I look forward to your research results.
Sous, et al. I drive, park overnight, and restart in snow country at elevations over 7,000 ft. with overnight temperatures ranging from +32F to -17F.
Should I use a lower viscosity oil?
You are welcome and I too look forward to the results of the UOA. As for your lower viscosity question, I would just be repeating/piggybacking on what the other fellas said, so I have snipped a bit of their words and quoted them below.
Originally Posted by RacinJasonWV
I would definitely do the synthetic 5w-40 in that case...
My oil change interval is 5k. Works for me. Everyone has an opinion on oil. Most of their opinions would be fine in practical use.
Originally Posted by SkySkiJason
It’s ok that we don’t all agree on everything. The world would get boring.
I agree, the lower viscosity oil definitely makes a difference in how SMOOTH the truck runs after a cooooold start, but all of that clanging and banging doesn’t hurt anything.
Originally Posted by z31freakify
I've said it many times, oil is oil as long as you change it regularly... Change it often and your engine will last forever.
...by reading old UOA it seem the 7.3 doesn't play nice with extended OCI's.
-------------------------------
Tim, I have selected 5,000 - 5,500 miles as my UOA benchmark in order to keep things on an even playing field. I am not comfortable in running conventional oil much past 5,000 WITHOUT being told that my engine is capable of doing so by a UOA. There are several companies out there that will do a UOA, but Blackstone makes it easy for us...
Once I am done "experimenting" with Rotella, Triax, TSC and maybe StictionRx, I will make an informed decision on the best suitable path forward for my application. That will be based on three things, in this order of importance...
1. Performance of the oil over ~5,000 miles based on a UOA
2. Cost per year based on 5,000 or 7,500 mile OCI
3. Availability (can I walk into a store and buy it or do I need to order it online and be backordered at times)
Sometimes cheaper is not better, but sometimes it is. Sometimes cheaper is the same as boutique/specialty priced, but sometimes not. Each person should perform their own analysis because my engine may exhibit completely different results than RacinJasonWV, Z31Freakify, SkySkiJason or anyone else on here. We cannot say "this oil is best" because we just don't know... We don't know your specific use of the vehicle, your expected use and your environment.
Picking on my friends - it makes ZERO sense to do a 5k mile OCI with synthetic oil.
I agree, the lower viscosity oil definitely makes a difference in how SMOOTH the truck runs after a cooooold start, but all of that clanging and banging doesn’t hurt anything.
My truck is a toy anymore. Takes a couple years (or even longer recently) to hit the 5k mark. So the cost isn’t that significant to me. I’m just not interested in doing oil testing and trying to extend it longer even if I can. Like you said, different strokes so the world isn’t boring. Lol
I do feel the trucks start easier and quicker in the winter with the lighter weight synthetic. And it made a huge difference on the cold start romps in my previous old 300k truck.
Pick your oil based off your needs and wants like we do our women.
You can like em round, skinny, tall, short, blonde or pink haired. Just don't argue about what type is best online.
I use synthetic because my cross country trips demand higher OCI than conventional can give me and get me back home before I have to change oil. Oil changes in campgrounds are frowned upon and I won't trust Billy making $5.25hr with my engine's health states away from home
Sous good on you! You are doing great service for the Brotherhood of 7.3L PSD owners. I look forward to your research results.
Sous, et al. I drive, park overnight, and restart in snow country at elevations over 7,000 ft. with overnight temperatures ranging from +32F to -17F.
Should I use a lower viscosity oil?
FWIW I run Schaeffer Supreme 9000 5W-40 year round on an 8,000 mile OCI in MN. It does very well. They have recently reformulated the oil and changed the name to SynShield® OTR Plus Full Synthetic 5W-40 so I don't know what effect that will have. I think they did it because the gasoline and diesel oil standards have diverged so far from each other they can no longer label the same oil as being compliant with both.
FWIW I run Schaeffer Supreme 9000 5W-40 year round on an 8,000 mile OCI in MN. It does very well. They have recently reformulated the oil and changed the name to SynShield® OTR Plus Full Synthetic 5W-40 so I don't know what effect that will have. I think they did it because the gasoline and diesel oil standards have diverged so far from each other they can no longer label the same oil as being compliant with both.
Good point. Tim, search the forums for some oil related threads. There has been talk about not using an oil that is dual rated for both gasoline and Diesel engines. There are compromises that occur in that situation which negatively effect what we like to see in an oil. The oil should only have a “C something” rating and no “S something” if I remember correctly. I say “something” because the last letter changes with new updates to the requirements.
Pick your oil based off your needs and wants like we do our women.
You can like em round, skinny, tall, short, blonde or pink haired. Just don't argue about what type is best online.
I use synthetic because my cross country trips demand higher OCI than conventional can give me and get me back home before I have to change oil. Oil changes in campgrounds are frowned upon and I won't trust Billy making $5.25hr with my engine's health states away from home
I traveled with empty gallon oil jugs and changed oil ‘illegally’ at campground many, many times using the fumoto drain valve. Fill last oil change containers with fumoto, then I put a hole in the oil filter and drain into a 1 gallon water container I cut the top out of, then remove filter with clean hands. Literally 10min oil changes and no mess. Take old oil to nearest autoparts store. No way I’m letting minimum wage DGAF’s work on my junk. Way too many stories of that going wrong and I certainly didn’t have time for that.
I use synthetic because my cross country trips demand higher OCI than conventional can give me and get me back home before I have to change oil. Oil changes in campgrounds are frowned upon and I won't trust Billy making $5.25hr with my engine's health states away from home
This is a consideration for most and you are right.
We installed Fumoto valves on our long distance travel vehicles years ago and I use a K&N filter with a 1" nut welded on the end. This means that I can change the oil without a jack, stands or any tools other than a 1" wrench if the filter is stuck.
While traveling cross country, I have changed oil at many places including campgrounds, parking lots, rest stops, etc. Usually it takes me less than 30 minutes taking care to not miss anything.
This is why the availability of the my oil choice is in the top 3 priorities for me. This is not a concern for everyone though and I get it.
This is a consideration for most and you are right.
We installed Fumoto valves on our long distance travel vehicles years ago and I use a K&N filter with a 1" nut welded on the end. This means that I can change the oil without a jack, stands or any tools other than a 1" wrench if the filter is stuck.
The nut isn’t needed if you drive a screwdriver or punch into the filter to drain it. You can use the screwdriver to twist filter loose. Plus, hole in filter means no mess.
I too punch a hole in the bottom of the oil filter after loosening. Once the oil has drained, I plug it with a golf tee then remove it with no further dribbles.