kirkland 5w-30, 3800 miles, Acura RDX 2020

[fantastic]

When lab says its greater than 5%, I guess it can not measure above 5%, maybe it was more 6 or 7, who knows.

I think I've seen over 5% shown from this lab before (6%,7%, etc). Maybe you can confirm?

We have the same car as tolian21 and see the same test results. We have another car for around town so the RDX see's mostly highway miles. I don't believe extended highway trips make much if any difference in burning the fuel off. This sample was taken right after 2 back to back 200 mile trips with temps in the mid 70's and the maintenance minder at 30%.

We use 87 octane in our car so I don't think that makes much difference with fuel dilution compared to premium either. Changing the oil at 50% oil life seems like a good way to go and that's what I went with at our last change.

View attachment 190676

This is very helpful thanks!

 

[tolian21]

another evidence that Honda 2.0t should be using Xw-30, which would keep your viscosity of where it was intended to be with 0w-20

 

[twX]

Yes, 87 is allowed but 93 is recommended
per manual. Someone said higher octane reduces fuel dilution, but maybe its not….

Using lower octane on an engine designed for higher octane will increase fuel dilution. The reason is that the engine will retard ignition timing, which reduces efficiency and requires more fuel to be injected for a given engine load.

At high load and rpm, fuel dilution goes up more or less exponentially with the injector firing time, since any additional fuel will need to be injected while the piston is low in the cylinder, which washes the cylinder walls with fuel. So a small increase in fuel flow can cause a large increase in the fuel dilution rate.

Using higher octane on an engine designed for lower octane shouldn't affect fuel dilution very much.

 

[Triple_Se7en]

^^^^^^^^^^This (first sentence)^^^^^^^^^

To the OP
I would land somewhere between 5w30 and 5w40. 0w40 is where I'd go next. Change at 5k.
That Iron number is high. Try another brand..... maybe NAPA, Fram or Quaker State to save a few $$.
Heck, try all-3.

 

[tolian21]

That Iron number is high

I think its slightly high, but its within the normal ranges, but its trending down compared to last two oil changes. I believe its still finishing initial break in since this engine only has 34k miles now.

 

[ZeeOSix]

If that's an above average trip length for you, it would reduce the dilution, but probably not that much. It might take a few hours with a warm engine for fuel dilution to drop a lot.

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Could you give some details on how that test was done to explain the increase from 0-10 hours, then the decrease from 10-30 hours. Was the oil being diluted with fuel the whole time as some constant dilution rate?

 

[ZeeOSix]

glad I went up in viscosity, 5w-30 now looks lower than 0w-20 thanks to all the fuel dilution.

Can you imagine if the engine was speced for and using a 0W-16 or 0W-8. Over 5% fuel dilution in only 3800 miles is pretty bad.

 

[tolian21]

Can you imagine if the engine was speced for and using a 0W-16 or 0W-8. Over 5% fuel dilution in only 3800 miles is pretty bad.

Yup, 5w-30 ends up with 7.6 cSt, which is lower than starting viscosity of 0w-20 that manufacture “recommends”.

 

[ZeeOSix]

Yup, 5w-30 ends up with 7.6 cSt, which is lower than starting viscosity of 0w-20 that manufacture “recommends”.

If the 5W-30 (which is probably around KV100 of 10 cSt) ends up at KV100 of 7.6 cSt, then the fuel dilution is more like 9%. "Oil #1" is fuel viscosity at 100C. 9% fuel mixed with oil that's 10.0 cSt at 100C makes the mix 7.6 cSt at 100C.

Did you ever monitor the oil level and see it increasing as the miles per put on this oil?

 

[tolian21]

Did you ever monitor the oil level and see it increasing as the miles per put on this oil?

I did not see any change in oil level. Also this 5w-30 came in after 0w-20, so maybe some old oil traces were still present. Maybe if oil burns off and replaced with fuel, in this case there might not be much change in the level.

 

[twX]

Could you give some details on how that test was done to explain the increase from 0-10 hours, then the decrease from 10-30 hours. Was the oil being diluted with fuel the whole time as some constant dilution rate?

From 0-10 hours, the engine was run with coolant and oil temperatures regulated to 40 C. After 10 hours, the temperatures were maintained at 80 C. I suspect that the rate of fuel entering the crankcase would have been very similar in each phase, but the rate of fuel loss from evaporation would have been much higher with the higher oil temperature.

The study is 2002-01-1647: Study of Fuel Dilution in Direct-Injection and Multipoint Injection Gasoline Engines.

The result of this test was only shown for the multipoint port injected version of the engine, but the DI version had similar dilution levels. They did other tests which showed dilution increasing with engine load and with injector timing retard.

 

[ZeeOSix]

From 0-10 hours, the engine was run with coolant and oil temperatures regulated to 40 C. After 10 hours, the temperatures were maintained at 80 C. I suspect that the rate of fuel entering the crankcase would have been very similar in each phase, but the rate of fuel loss from evaporation would have been much higher with the higher oil temperature.

I would think the fuel dilution rate was much less when the engine was at the 80C operating temperature, which also helped the dilution rate to decrease starting at the 10 hour point during the 80C test phase. That first 10 hours was like running the engine for 10 hours in the "warm-up" stage. Would have been interesting to see what that graph would look like as the oil and coolant temps went lower than 40C for the first 10 hours.

 

[JavierH19]

I'd bump to 40 being me.

 

[twX]

I would think the fuel dilution rate was much less when the engine was at the 80C operating temperature, which also helped the dilution rate to decrease starting at the 10 hour point during the 80C test phase. That first 10 hours was like running the engine for 10 hours in the "warm-up" stage. Would have been interesting to see what that graph would look like as the oil and coolant temps went lower than 40C for the first 10 hours.

Thinking about this some more, I do think the fuel dilution rate would be higher as well. There would be more blow-by with the cooler engine, but maybe not that much more, since the pistons and cylinder walls should be fairly close to normal temperature in these steady state conditions. More blow-by should also help vaporized fuel escape to the combustion chamber though.

The colder engine would also need more fuel injected to produce the same torque output. Fuel might condense more easily on the colder cylinder walls as well.

In a real cold start scenario, the dilution rates would probably be even higher due to post-start fuel enrichment, and much colder cylinders shortly after the engine was started.

 

[GW208]

I did not see any change in oil level. Also this 5w-30 came in after 0w-20, so maybe some old oil traces were still present. Maybe if oil burns off and replaced with fuel, in this case there might not be much change in the level.

The oil level in our car has never changed either and I've never smelled fuel when changing the oil. You would think that with greater than 5% fuel dilution you could smell it or see it on the dipstick?

 

[tolian21]

The oil level in our car has never changed either and I've never smelled fuel when changing the oil. You would think that with greater than 5% fuel dilution you could smell it or see it on the dipstick?

I could smell some traces of gasoline, or so I thought, turns out I was right.