If they both have the same energy content then why does ethanol free typically get better mileag?
Valvoline Modern Engine 0w-20 - 4.8K miles; 2016 Honda Accord K24W 23k miles
- Thread starter cutlassvillager
- Start date
I apologize I misunderstood your question. Ethanol free gasoline has a higher energy content that is true. I thought we were talking about “burn speed” or some other aspect.
The only difference is the fuel’s resistance to premature self ignition.
The engine can advance timing much more with premium fuel because there’s less chance of knock. That’s how it makes more power.
I still haven’t figured out what that has to do with fuel dilution other then simply a more complete burn and less fuel getting past the piston rings and getting into the oil. 🤷🏻♂️
The engine can advance timing much more with premium fuel because there’s less chance of knock. That’s how it makes more power.
I still haven’t figured out what that has to do with fuel dilution other then simply a more complete burn and less fuel getting past the piston rings and getting into the oil. 🤷🏻♂️
A higher compression ratio is more efficient because it has a higher corresponding expansion ratio. The burn is just as complete for a lower rating or ratio unless there is something wrong with the engine or its design. Higher compression gives higher thermodynamic efficiency.
Thanks for the heads up on this. I am familiar with the 1.5T dilution problems, but had no idea the 2.4L NA engine had some issues too. I'll consider changing to 91/93 for sure. I always ran Premium in my previous vehicle (and still do in my 3-series) and this gets a lot better MPG! What is the theory behind this: cleaner burn = less wasted fuel that makes its way to the sump?
I am going to run another similar OCI and do another UOA. I have some longer trips coming up so this should be a little different (better?) usage as well.
I am glad I took a UOA too! I didn't see anything that jumped out as abnormal - No check engine lights and I regularly checked the oil level and didn't notice any significant increase or decrease but I checked less frequently once I felt comfortable that everything seemed normal. From what I recall it looked like usual dirty oil. Now that I know there could be an oil dilution problem I'll keep a closer eye on color, smell, level, etc.
I'm hoping I can eventually get to the point where I feel comfortable running it down to 15%!
I won a K24W DI as well and yes, fuel dilution is an issue. My experience is that Interstate driving actually promotes fuel dilution as does cold weather short-tripping. It seems to do best with longer, suburban drives at modest speeds. I’ve played around with gasoline grades with no conclusion other than 91/93 octane doesn’t help. I use 89 because the engine seems more responsive (YMMV).
The only thing I’ve tried that seems to help is moving to 5w-30. Why this is not clear to me but maybe a thicker oil creates a better piston ring seal than a fuel-diluted 20-weight.
Not sure any of this really matters, but I do wish DI wasn’t present. Oh, and I usually change when the MM gets to 60% or so and await the chastisement from board members for doing so.
Quick update - now that I am paying closer attention I have noticed in our recent 10-20 degree Fahrenheit weather the car can take longer than any other vehicle I've owned to reach operating temperature. If I leave and start driving right away (esp. straight to the highway), it warms up quicker but if I'm immediately stuck in stop and go traffic it seems to take longer. Once it reaches full temp it can maintain it just fine, I never have any problems heating the interior, no CEL, etc. Reading a bit on other forums 9th gen owners seem to experience the same thing. I have a feeling this is a contributor to the fuel dilution. Definitely planning on changing early again - probably when OLM is at 50%!
The Ecoboost guys have had a lot of luck with the various Castrol Synthetics when it comes to holding up to fuel dilution. They seem to shear less than other brands when fuel diluted.
I'm not sure what that Valvoline TBN starts at but to be at 2 in just over 4k miles seems a bit low to me and perhaps indicates that the oil is not as stout as some other choices...or could just be due to the fuel dilution. Would you consider running a different brand of oil under the same circumstances just to compare??
I've noticed Castrol does retain its viscosity quite well.
Thanks for the info here! - I ran a tank of 89 and it does seem a bit more responsive and less vibration at idle. Not that it had problems before, just a slight improvement. I'll try switching back and forth a bit more to see if it is more of a placebo effect or not. Based on this UOA (and assuming no change with the 2nd) I will be changing around the same time too - 60-50%.