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Should I switch to synthetic?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by david85, May 5, 2018.

  1. david85

    david85 Full Access Member

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    As the title says.

    The engine probably has about 50k miles since the rebuild and doesn't leak or use any measurable amount of oil between changes. A little spooky actually, considering how much it used to use. Right now I run Shell Rotella 15W-40 and the powerstroke style oversize filter. I read some say rotella isn't a good choice for the IDI, but other than high consumption, I'm couldn't find any other reason during my forum search.

    I have no plans to sell the truck and wonder if the better oil is worth the cost. Even 0.5mpg increase would theoretically be worth it. I'm also using it as a daily for a short commute, and wonder if the cold performance of synthetic might help reduce the higher wear & tear per mile during the warmup cycle (yeah, it's my baby...).

    So is it worth the change over? Or should I just stick to dino and increase the change interval?
     
  2. genscripter

    genscripter Full Access Member

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    I was always told that if you didn't start with synthetic, then it's not worth converting to synthetic that had conventional run in it for a while. Something about how the synthetic oil won't bond with the engine parts if conventional was already in the crankcase. I don't know the validity of that assertion, just passing along when I heard.

    I always stuck to running conventional oil in my IDI because with the miles I put on it, I wasn't about to buy three gallons of $25 synthetic Rotella every 5000-7500 miles. Conventional is pretty affordable, so I stuck with that.

    But in my Jetta TDI, I always run synthetic Rotella since I first bought it.
     
  3. 79jasper

    79jasper Chickenhawk

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    If can help with extremely cold starting.
    You would see more gain by swapping gear oils and wheel bearing grease to synthetic. Lol
    Just swapping engine oil, likely won't see any difference.

    Sent from my SM-G892A using Tapatalk
     
  4. Hydro-idi

    Hydro-idi Full Access Member

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    I don’t believe synthetic oil in an engine will net you better fuel mileage. A thinner weight oil might.
    People mainly run synthetic oils when they want to achieve longer change intervals, as synthetic oils tend to hold up a bit longer before breaking down.
    I would run it if you want, but that old idi engine is not going to care what type oil you put in it.
     
  5. franklin2

    franklin2 Full Access Member

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    If one of your reasons for running synthetic is to reduce the number of oil changes, I am not sure I would do it. I think pull the old oil out, and all the nasty stuff that is in it, would be better for the engine than letting a dirty synthetic run longer, even if it is a better oil.
     
    nostrokes and Macrobb like this.
  6. david85

    david85 Full Access Member

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    I've been running 10k kilometers (6100 miles) between changes but that may be too long from what I've been reading. My truck rarely gets used hard and the short commutes are the worst of it right now. The engine is also coming out of a long sedentary period from when the body was getting restored. If nothing else, I might just to an early change this season.

    One thing I saw mentioned on another thread was the idea that synthetic might be more able to get past the valve stem seals and properly lubricate the guides. As I mentioned earlier, this thing doesn't use any oil, so I suspect the stem seals are very tight, which can cause problems. I know the heads were overhauled but I don't remember what type of guides were installed before I bought them.
     
  7. Thatoneguy

    Thatoneguy Full Access Member

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    I run syn blend rotella right now. But I think I'll try full synthetic. The way I see it, I rely on this truck every day to earn a living, and anything I can do to prolong her life and keep it healthy, is worth it! I tow a good bit too.
     
  8. DrCharles

    DrCharles Full Access Member

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    I have no experience with synthetic in IDI's, but I will share one strange diesel experience:

    About 20 years ago I acquired a '73 Mercedes 220D (a whopping 60 flywheel hp from its little 2.2 4-cylinder coffee-grinder in a 3000 lb sedan) with a bad rod knock. I tore it down and completely rebuilt it; had a shop go through the IP and injectors too. Ran like a very slow but reliable clock.

    After initial break-in I wanted to run it on synthetic oil too. But it actually "pinged" every time I stepped on the throttle (yes, this engine had a pneumatic governor so it had a throttle). Oil pressure was fine, same weight oil. Sounded like a tin can with small marbles in it. I drained it and put dino oil back in - no more noise, 50k trouble free miles until the body cancered out.

    I can only surmise that the synth oil was being burned in the cylinder, and not smoothly...
     
  9. Runningaford

    Runningaford Registered User

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    I've got to check, I think I've got a Mobil synthetic blend in right now. I had used Shell Rotella, and as already read a lot on here, my engine would eat the oil. Once switched, it stopped.

    This next time around, I'm going to run a little MMO in it; as I always have a single stuck lifter in the winter that's annoying; I'd think it's just from sludge that needs cleaned out.
     
  10. 79jasper

    79jasper Chickenhawk

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    Skip the rochitta.
    They valvoline premium blue synthetic, Mobil delvac synthetic, mobil 1, (or I can give you contact info for some of the best oil out there, just be prepared for the sticker shock. About $30/gal Lol but it's all I'll run anymore)
    Hell, even traveller from tsc is better. Lol

    Sent from my SM-G892A using Tapatalk
     
  11. david85

    david85 Full Access Member

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    So other than high consumption (which I don't have), what is so bad about rotella? It seems a lot of guys don't like it, but I haven't found a detailed description for why. If there is a good reason, I'll happily stop using it even if I switch to another dino oil.
     
  12. compressionignitionrules

    compressionignitionrules Full Access Member

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    stick with your rotella T , 15/40 in the summer . when the weather cools down preparing for winter make your oil change to a 5w30 diesel oil.

    easier cranking in winter and might just use a bit ................... faster oil to all the top end parts too.

    I switched multigrades for years and it never hurt an idi.

    or just plug it in regularly?
     
  13. snicklas

    snicklas 6.0 and Loving It!! Staff Member

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    David,

    Here is my experience with switching to synthetic. This is on a few different engines, not all diesel.

    The first one I switched to full synthetic was my 03 6.0 Excursion. One of the best "upgrades" I've done to the truck. Starts easier, runs better, and it doesn't use any oil, didn't with conventional. It's at ~171,000 and just now had my first injector issue... still has all 8 factory injectors and the factory HPOP. Also factory turbo and head gaskets. So 15 years and 171,000+ miles with no issues, I believe running the better oil (Chevron Delo 5W-40 Full Synthetic) and good filters, changing at 5,000 miles has helped reach this.

    The second was my 91 Jetta IDI. It was switched because I had the oil for the 6.0. To use the same oil in both and change the oil, I only needed to buy one extra gallon. The 6.0 holds 15 quarts, the Jetta 5. It had right at 300,000 on it when I switched. Oil consumption didn't change between conventional and synthetic, about a quart per oil change cycle. Was still running synthetic when I sold it.

    I also switched my 2 single cylinder Kohler air cooled engines (14 an 16 HP). I had been using Motorcraft 15w-40 Diesel Oil (left over from the 6.0) and they seemed to like it. They call for Straight 30 weight. When I did my spring oil change, I used the Chevron Delo 5w-40 since I had some on hand. These DID NOT seem to like that oil. I mowed once, noticed increased consumption, and noticed at lower throttle levels, when I had the headlights on, it would haze blue (burning oil). I switched both back to Motorcraft 15w-40 Diesel Oil and they went back to normal. One hadn't been ran, I switched it where it sat. I now have gone back to Straight 30 Weight, that, or the conventional diesel oil seems to work better.

    I also switched my 2000 P71 Crown Vic to the Castrol High Mileage Synthetic Blend oil. Corey @Dieselcrawler recommended it, for the Ford "mod motors" to help in oil consumption and burning oil. I switched it and consumption when down (it still consumed oil, but not as much), and the smoke out the exhaust completely quit. Because of this, I have run this oil in my 07 P71 and the Infinity QX65 (5.6L V8). They both seem to like this oil.

    [​IMG]

    I'd say go for it. But don't expect a drastic changes. With the condition of your engine, you should be good, and it may help to prolong the life. I would not go super long on the OIC, but you might be able to stretch it out a bit. I still change the 6.0 at the recommend 5000 miles interval, because of the shearing the 6.0 Injectors cause of the oil. I even keep the gasses at the 3-5000 mile interval. I keep my vehicle for a long time... so changing the oil a bit more often is cheaper in the long run (at least in my opinion, I can afford a few buck more in oil than a sever thousand dollar rebuild).

    Now, for the 7.3 IDI I have now, it leaks enough, that I'm going to stick with conventional. Right now I have a case of Mobil Delvac 15w-40 because it was on sale at Sam's Club ($34 a case). I'm going to change the rocker cover gaskets, and see what else might leak. This truck isn't planned to be a daily driver, or a complete restoration. So as I make improvements, it may get switched over to synthetic, but right now, it will stick with conventional, since changing the oil every 3000 miles won't be that often.

    I like synthetics, but would say try them, see how YOUR engine responds to it. It may like it, it might not. I've seen both in different applications, and have made adjustments accordingly.
     
    79jasper and david85 like this.
  14. david85

    david85 Full Access Member

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    snickas, thanks for the thorough feedback. That's exactly the kind of info I was hoping for. And I agree that a drastic improvement is not to be expected.

    I'll jot that down as another vote for delo 5-40 syntheytic. Looks like the price isn't as big a jump as I thought either so I don't mind giving it a try to see what happens. My plan is to maintain roughly 6000 mile drain intervals.

    I've tried to stick with either baldwin or motorcraft filters, so hopefully I'm good in that department. I hear fram has some "premium" filters that might be good, but I still get a cold sweat whenever I hear the term "fram oil filter".
     
  15. 79jasper

    79jasper Chickenhawk

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    Also, don't over look bypass filters.

    Sent from my SM-G892A using Tapatalk
     

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