what oil for fuel dilution problem?

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I've been using Biosyn in my Subaru H6 engine for awhile now, with good results. I started using it because of a fuel dilution issue. The fuel dilution still exists but I'm looking for a cheaper alternative to the Biosyn. I want to stay with a synthetic oil. A couple that come to mind are Pennzoil 10w30 and Mobil 1 10w30 HM. I haven't been a fan of Mobil 1 in recent years but the 10w30 High Mileage caught my attention becuse it's a little thicker and carries the ACEA A3 rating. I used Castrol 0w30 (German) in this engine prior to switching to Biosyn and it was OK but not great in terms of dealing with the fuel dilution. I still have some of it and will use it if there is nothing better out there. I'm interested in hearing from anyone who has an opinion on what I should be using. I want to stick with oil that I can buy off the shelf at my local auto parts store, so that eliminates Amsoil, Redline and the like.
 
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This is going a bit off topic, but I had a fuel dilution issue with my truck that I dealt with recently. It turned out the the thermostat. Might be a simple, cheap fix.
 

harrydog

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 Originally Posted By: Pablo
So why not fix the cause of the fuel dilution?
I wish it were that easy. I've worked with Terry Dyson on this problem for awhile now and the fuel dilution was reduced somewhat but not eliminated. I could try replacing the injectors but that would be quite expensive and might not even solve the problem. That's why I'm looking for an oil that might handle fuel dilution better than most.
 
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Shell Rotella T 5w-40 seems to work well in subaru engines and is reasonably priced (compared to other synthetics). It starts out thick, so even if the fuel dilution brings it down to a 30-weight, you should still be covered. But I agree with others - if you're planning to hold onto this car - fix the cause of the issue instead of trying to deal with the symptoms. By the way, what OCI are you running?
 
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harrydog

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 Originally Posted By: Quattro Pete
Shell Rotella T 5w-40 seems to work well in subaru engines and is reasonably priced (compared to other synthetics). It starts out thick, so even if the fuel dilution brings it down to a 30-weight, you should still be covered. But I agree with others - if you're planning to hold onto this car - fix the cause of the issue instead of trying to deal with the symptoms. By the way, what OCI are you running?
I've been running 6,000 OCI's with the RLI but it could probably go longer. I'll be doing 5,000 OCI's with whatever off the shelf oil I end up using. I would fix the cause if I knew for sure what the cause was.
 
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Unfortunately, some vehicles are prone to fuel dilution more than others. Many are as a result of short commutes or long idling times. The UOA section might offer you some insight to some oils that hold up better than others with this situation. Frequent oil changes seem to be your best bet though, and seems to coincide with manufacturer severe conditions maintenance schedules. In one of my vehicles, I found Schaeffers #703 to do well. Better than PP and MaxLife syn from a UOA standpoint. I have an HDEO (LE8130) in it now, hoping that will be the ticket for the future of this already 10 year old truck.
 
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The Subaru H6 engines seem to have fuel dilution problems. I Auto RX'd my moms 2002 H6 Outback and it significantly reduced the fuel smell in the oil. I've never done a UOA on it, so I don't know what the numbers would be.
 
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Marine engines are notorious fuel dilutors. The newer FI ones are a little better, but still pretty bad. The historical remedy with marine engines is to run a single vis oil. You may have other issues with that in a Subie. But that is how we deal with it on the water. I'm not aware of any other "off-the-shelf" oils that are significantly better at coping with it. Otherwise, the biosyn you have been running is about the best solution I am aware of for heavy dilution conditions. That, or shorten the change interval to compensate.
 

JDD

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If you can't/won't fix the problem, just change out the oil more often with a sale priced dino, and do the filter every other change. No need to go expensive syn.
 
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Sequim, WA
Rotella T 10W-30 is a good non synthetic option. That's what I run in my Legacy GT. Terry recommended this oil when we were working with my WRX and its fuel dilution issues. Ed
 
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San Jose, CA
Mobil 1 0w-40. It meets the special specs for many turbo cars which are prone to fuel dilution - Porsche, Audi, Nissan GTR etc. And it is Porsche (boxer engine) approved. I think it's the best off-the-shelve oil for a Subaru (and more so for a turbo Subaru).
 

harrydog

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 Originally Posted By: edhackett
Rotella T 10W-30 is a good non synthetic option. That's what I run in my Legacy GT. Terry recommended this oil when we were working with my WRX and its fuel dilution issues. Ed
Did you have any UOA's done with the Rotella T?
 

harrydog

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 Originally Posted By: SilverGGA
Mobil 1 0w-40. It meets the special specs for many turbo cars which are prone to fuel dilution - Porsche, Audi, Nissan GTR etc. And it is Porsche (boxer engine) approved. I think it's the best off-the-shelve oil for a Subaru (and more so for a turbo Subaru).
Where do they sell it? I don't recall seeing it anywhere locally.
 
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