A new mechanic for big rig diesel trucks found a leak from the turbo to engine and fixed it with ROUND o rings instead of the SQUARE o rings it had. He said that it would improve my MPG. And it did. I went from 8 MPG to 10 MPG. Yes, a little better. In our conversation I mentioned that since I live in the city of eternal springtime (cold is mid 50s and highs are high 80s) that I have been using straight 40 weight diesel oil. Commenting on the complexity of the injectors (hi pressure oil, electric, etc) he said that some of these newer big truck engines sometimes wont even start unless they have 15w 40 oil. He said that it could make a difference in bettering my MPG. What do you think? Next oil change I will try the 15w 40 and see. Untill then I will see if the turbo leak fix and the new washers on fuel pump help. hasta manana.

 

Personally i couldnt say. All 4 of my 7.3 have had 15w40 and nothing else. My present truck was owned previously by a good friend. One winter he tried the thinner oil route as per average temp. He is a tightazz but after the change he only drove it for days before changing the oil again back to 15w40. He said it ran bad and idled bad. I personally did not experience it but we spoke about it both before he did it and after. I do know also when i towed my camper and oil temp got hot it idled badly. I swapped a colder thermostat in to get oil temp down and it is good. Mind you thats in 95° heat in summer towing hard at 11-1200 egt .

I dont understand how turbo pedestal orings would affect mpg . Oe seals are round factory but over time get squished flat.

 

I didn't know you could still get a straight 40 weight oil, especially rated for diesel. I haven't seen any straight weight oil recommended for anything in 20 years with the exception of small motors like lawn mowers and such.

 

The only straight 40w oil thats sold around here doesn't meet the requirements for the 7.3. Straight 40w is diesel only rated and is low ash for 2 stroke detroits. I would make sure you use a oil that meets the requirements of the 7.3.

 

Here in my country you can get a sraight 40 weigt oil rated for diesel from PEMEX, IDK if it meets the requirements for the 7.3. I use 15W40 that meets the requirements, in my truck

 

A real syn oil could help injector performance. I run this in both of my Mercedes Diesel engines - https://www.redlineoil.com/15w40-diesel-motor-oil They receive one year OCIs and it still has life left according to Blackstone.

It would be in the PSD but it is consuming oil and I have yet to find the source (me thinks injector orings). At least it is not an external leak.

I would not run a straight 40 weight, even if available. Consider looking up what Ford spec'd in 2003 when the last of the 7.3s rolled off the line.

 

You know, it might be available here, it's just that I've never looked for it, so I've never seen it.

 

i'ma kinda skip ahead here and not read comments.


The o-rings that go in there are round.

The reason they are square when you take them out is due to crush and heat. This is why you NEVER re-use o-rings when you do turbo work and such.


The straight 40 weight will never let the injectors work properly as they fire with oil.
When the oil works out to temp, your truck then builds power.

Run the 15w40 these are rated for and you'll see better performance.

 

i run that rotella t6 becuase it will not start in -20f in the winter if i run that thicker oil. one thing that i noticed is when it get that cold it will leak and use oil allot faster i think its due to the injector orings being 270000 miles old and 18 years on them. im trying to find a good source for the injector orings so i can do them this summer, did the oil cooler orings and gaskets a summer or 2 ago and that dont leak a drop anymore no matter the temp now.

 

You can order injector o-rings from our Sponsor; Rosewood Diesel.

You can also order from RiffRaff Diesel as well.

 

if your fuel filter is dark in color, your injector orings are leaking

 

When he said square cut o rings, was he talking about boost loss rather than oil loss? There is one o ring right at the turbo that he could have been losing boost from

 

Ehhhh,

Yes and no.

 

I had a discussion with an oil guy a few months back.
He said they had a new oil out for the big rigs, which was 10w-30, and that they claim extended intervals at that. With some trucks going 80k on an oil change with no issue. This, supposedly, saves companies with big fleets millions of dollars from doing fewer oil changes (oil, filter, mechanic's labor).
It sounds good and all, but I know my cousin's Series 60 starts to consume oil at an alarming rate beginning at 12k - 13k miles on the oil and he knows at that point he needs to get it changed quick. The oil guy didn't have a real good answer to that other than "try our oil" (which happens to cost many, many times what regular diesel rated oil costs).
So take that from a salesman for what it's worth.

Anyway, for the 7.3 stick with the tried and true 15w-40, or if you want to go synthetic, there are many options there for a different viscosity.

 

When your oil level is suddenly low and your truck doesn't leak, its time to change the oil soon as the oil is breaking down and loosing volume.

HEUI injector systems destroy oil.

Best to use a moly based oil if anything you wanna do something fancy.
If youre looking to increase life you need to run a bypass filter to try and filter out as much soot as possible as the standard filter bearly filters out soot.