Should fuel dilution impact your oil choice?

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Let me see if I've got this right; feel free to correct me...

Generally speaking, the shorter your driving trips, the less your motor and its oil reach a normal operating temperature and the more fuel dilution can be a problem. Correct so far?

In the SUS Viscosity @ 210°F section (http://www.bobistheoilguy.com/engine-oil-analysis/), it's noted, "That means the sample had a 2.4% viscosity loss over its service life due mainly to shearing and slight fuel dilution. Oils such as Castrol Edge 5w30 are on the thinner end of the 30 weight spectrum, and are on the borderline of being a “thick” 20 weight oil straight from the bottle."

So my questions are -

1.) Should short trips, which tend to cause fuel dilution, impact your oil choice?

2.) How do you know which oils are "thin" versus "thick" in a given grade?

I'm thinking of my Wife's Volvo 2001 S40 which has a whopping 48,000 miles on because she/we mostly makes short trips to the grocery store, etc. I'm due to change the oil and I've always used 5W-30 M1-EP so I just want to be sure I'm making a smart oil choice.

Thanks for you feedback and opinions!

smile.gif


Ed
 
Anything that meets the manufacturer spec or oil will be fine. But if the vehicle mostly gets trips that don't allow the engine to get up to operating temperature, then I'd take it for a nice highway cruise of an hour or so every few weeks, and keep the OCI to 5k miles. Fuel dilution is much more of an issue with DI engines than with short trips. Now if you combine the two (short trips with a DI engine)...
 
It doesn't for me as I addressed the fuel dilution first. once it was removed, I then picked the oil I liked best.
 
I moved my Ecoboost F150 to a 0w-40 oil as an edge against the obvious fuel dilution these engines have. At the end of a 4k run its still in pretty fair shape. No real empirical data such as a UOA, I just notice that the 0w-40 comes out looking like ordinary motor oil instead of varsol, which is what the PP and PU looked like after being run through the wringer.
 
If you're talking high performance and want to deal with fuel dilution there is an oil company, RLI that has developed oil specifically formulated to deal with fuel dilution for high performance turbocharged engines. They developed it in cooperation with a customer that owned an Audi and Terry Dyson the analysis work.

You can actually call RLI and talk to them about the oil. You probably don't need to go to such lengths to take care of fuel dilution for the average daily driver but here is a solution if you choose to go that way. The results were very good and they were all verified by very detailed UOA's done by Terry.
 
I would suggest that if one is worried about initial viscosity with respect to fuel dilution (or anything else for that matter), there's not a lot to be gained by splitting hairs within the exact same grade and service classification. Most 5w-30 SN/GF-5 oils are going to be extremely close in HTHS. Even the 10w-30 SN/GF-5 oils won't be significantly thicker with respect to HTHS.

With the serious fuel dilution my old truck used to endure, the solution was a non-ILSAC 5w-30 in the winter and a 15w-40 in the winter to keep oil pressures in order. I should hope that the average properly running fuel injected vehicle wouldn't need anywhere near that drastic of a solution.

As was already mentioned, if fuel dilution is an issue, there is some wisdom in watching the OCI.
 
Originally Posted By: OneEyeJack
If you're talking high performance and want to deal with fuel dilution there is an oil company, RLI that has developed oil specifically formulated to deal with fuel dilution for high performance turbocharged engines. They developed it in cooperation with a customer that owned an Audi and Terry Dyson the analysis work.

You can actually call RLI and talk to them about the oil. You probably don't need to go to such lengths to take care of fuel dilution for the average daily driver but here is a solution if you choose to go that way. The results were very good and they were all verified by very detailed UOA's done by Terry.


This ^^. I recall when that work was taking place; several years ago now. Not sure if newer direct injection engines have similar levels of fuel dilution or not.

I'll also add that fuel dilution levels rose very soon in the OCI, and more frequent oil changes did virtually nothing to offset the problem if I remember correctly.
 
Originally Posted By: wallyuwl
Fuel dilution is much more of an issue with DI engines than with short trips. Now if you combine the two (short trips with a DI engine)...


All my problem with fuel dilution has been with the short trips, not the DI engine. Only when a DI engine was doing short trips did it become noticable. All my DI engines that WEREN'T short trippers haven't showed any fuel dilution.

Makes we want to take a non-EGR, non-DI motor and let it go only short trips for 2000 miles and see if fuel dilution shows up just as bad as it does the DI?
 
Originally Posted By: Brian Barnhart
Originally Posted By: OneEyeJack
If you're talking high performance and want to deal with fuel dilution there is an oil company, RLI that has developed oil specifically formulated to deal with fuel dilution for high performance turbocharged engines. They developed it in cooperation with a customer that owned an Audi and Terry Dyson the analysis work.

You can actually call RLI and talk to them about the oil. You probably don't need to go to such lengths to take care of fuel dilution for the average daily driver but here is a solution if you choose to go that way. The results were very good and they were all verified by very detailed UOA's done by Terry.


This ^^. I recall when that work was taking place; several years ago now. Not sure if newer direct injection engines have similar levels of fuel dilution or not.

I'll also add that fuel dilution levels rose very soon in the OCI, and more frequent oil changes did virtually nothing to offset the problem if I remember correctly.


One other point regarding the earlier work (if I remember correctly); wear metals were still above normal even when a thicker oil viscosity was used to compensate for thinning from fuel dilution. (Apparently the presence of fuel was negatively affecting more than just the oil's viscosity).
 
Originally Posted By: badtlc
It doesn't for me as I addressed the fuel dilution first.

How do you address it if you've got a very short commute? Are you going to go out of your way to take the vehicle on long drives and burn fuel needlessly?
 
Originally Posted By: Ed_Flecko
So my questions are -

1.) Should short trips, which tend to cause fuel dilution, impact your oil choice?

Maybe. You could pick something a grade thicker. Or just consider changing the oil more often.

Quote:

2.) How do you know which oils are "thin" versus "thick" in a given grade?

By looking at its spec sheet and seeing where it falls on the viscosity chart.
 
Originally Posted By: Quattro Pete

By looking at its spec sheet and seeing where it falls on the viscosity chart.


Thanks Pete!

smile.gif


Can you give me an example of what you're specifically referring to, i.e., the viscosity chart???

Ed
 
Originally Posted By: Brian Barnhart
Originally Posted By: Brian Barnhart
Originally Posted By: OneEyeJack
If you're talking high performance and want to deal with fuel dilution there is an oil company, RLI that has developed oil specifically formulated to deal with fuel dilution for high performance turbocharged engines. They developed it in cooperation with a customer that owned an Audi and Terry Dyson the analysis work.

You can actually call RLI and talk to them about the oil. You probably don't need to go to such lengths to take care of fuel dilution for the average daily driver but here is a solution if you choose to go that way. The results were very good and they were all verified by very detailed UOA's done by Terry.


This ^^. I recall when that work was taking place; several years ago now. Not sure if newer direct injection engines have similar levels of fuel dilution or not.

I'll also add that fuel dilution levels rose very soon in the OCI, and more frequent oil changes did virtually nothing to offset the problem if I remember correctly.


One other point regarding the earlier work (if I remember correctly); wear metals were still above normal even when a thicker oil viscosity was used to compensate for thinning from fuel dilution. (Apparently the presence of fuel was negatively affecting more than just the oil's viscosity).


Which on its own means nothing,absolutely nothing and isn't a reason to switch anything.
 
Originally Posted By: Quattro Pete
Originally Posted By: badtlc
It doesn't for me as I addressed the fuel dilution first.

How do you address it if you've got a very short commute? Are you going to go out of your way to take the vehicle on long drives and burn fuel needlessly?


No. I do a lot of city driving. Running premium fuel eliminated the issue for me as it leans out the A:F ratio.
 
Terry alluded to it yonks ago, that fuel dilution wasn't simply a thinning out like the kero in the WW2 aero engine sumps, but was an actual reaction phenomena that took place, and was sometimes, depending on oil irreversible.

I believe that the choice of oil will help in the above, but have no experience or idea where to start...other than to use the google search of BIOTG, using the terms "dillution audi terry", as the Audis were the early adopter of destroying oils back in the day.
 
Originally Posted By: badtlc
No. I do a lot of city driving. Running premium fuel eliminated the issue for me as it leans out the A:F ratio.

Doing a lot of city driving is no problem, just as long as it's not just 3 miles and then park for 8 hours, like in my wife's case. Today was a fairly warm day, and at the end of these 3 miles, the oil temp hasn't even reached 140F. And during winter, it's even worse.

I can't imagine premium fuel making much difference. Looking at various UOAs, I can't see any such pattern.
 
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