Agree, TBN is fine, its a fuel that reduces viscosity.

 

Sulfur is present in gasoline and diesel because both fuels are derived from crude oil, which has sulfur as part of its chemical makeup. When the fuel is burned in the engine, it converts to sulfur dioxide. Overnight, condensation can occur inside the resting engine which, when it (the sulfuric dioxide) mixes with the sulfur dioxide, turns into sulfuric acid. It's this acid that causes the most harm because it corrodes the engine parts. The "Base" in the TBN neutralizes the acid that's mixed with the engine oil to minimize metal corrosion and thus, engine wear.

Why a TBN additive is more widely used for diesel engines is because diesel fuel has more sulfur than gasoline.

Because the RDX's 2.0 liter engine lets in more gasoline into the combustion chambers which then drips into the crankcase is the key issue, if I'm understanding the problem correctly. The high-pressure induction of air from the turbocharger and direct gasoline injection are probably to blame. A quick search shows that Audi, one of the pioneers of the 2.0L turbo configuration, also has fuel dilution problems.

Until Honda-Acura resolves the problem, I suppose as consumers we just need to take extra precautions. One of them looks to be adding a TBN additive and/or shorter oil change intervals.

 

when I change oil at 4K miles, TBN is pretty high, 3.5-4, which is considered good. Now sure why I need to make it even higher?

 

No need, then.

 

The sulfuric acid and viscosity are two separate issues.

 

Apparently they are directly related but not in the way I first assumed, which is that acid thins the oil. According to an article from the US Dept of Energy, Office of Scientific & Technical Information, sulfuric acid interacting with oil results in "thickening and coagulation of the asphaltenes and a partial condensation of tars which leads to the formation of a highly viscous mass of acid tar."

The article indicates a much more serious outcome when gasoline mixes with the oil, that of oil passages being blocked by a "viscous mass of acid tar." Yes, sulfuric acid does increase oil viscosity but worse, it produces tar that causes oil starvation.

 

Thanks for that information. I didn’t realize acid lead to tar formation like that. But unless you are really beating the crap out of your oil and not changing it on a regular basis, the TBN shouldn’t be zero. I have never seen an oil analysis where TBN was an issue. Your oil is going to get diluted by gas starting pretty much right away so the viscosity is going to tank way before an increase in viscosity is going to be an issue. That’s why people are recommending using a 30 weight oil and not caring so much about finding a really high TBN oil.

 

I still change my oil every 4k miles.

 

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I think this is the ideal preventive measure for engine wear due to high fuel dilution.

 

I only change filter every other oil change to save time. Very easy oil change. Got Kirkland oil at costco on sale for $32 for 2x5qt.

 

My wife drive RDX 2022 for short trips roughly 5000 KM per year. I thought the dilution mainly happens in winter time, so I decided to change oil right before and after winter to mitigate the issue.
I changed oil in 2023 Sept, and changed again in 2024 April. It seems working since I didn't notice dilution in April. So I relaxed a bit.
When I changed the oil today to prepare for the winter, oh my! the engine oil is thin like water, rushing out way further than I expected and spilling on the ground.
So i measured the oil drained out, it's almost 6L. I usually just dumped the whole 4.7L kirkland oil in, with a little bit extra prefill in the filter. So it would be less than 5L I put in. After 7 relatively warm months, I got almost a liter of gas in the oil!

This seems not just a cold weather issue, and I need to increase the changing frequency regardless of weather.

Probably I'll take the skipping filter approach to save the mess as well.

 

Cold doesn’t mean freezing weather. It just means the engine hasn’t had enough time to reach operating temperature. I had an oil change in the summer as well, after 3500 km, and my fuel dilution was 7.17%. If it wasn’t for that, the oil could have been used for thousands more km.

Best thing to do is use a higher grade oil like 0w30. The fuel dilution will still happen but your viscosity will be diluted back to a 0w-20 grade. If you use 0w-20, the dilution will make your oil thinner than a 0w-16 long before your oil is due for a change.

 

Has anyone heard of an oil catch can and PCV valve delete to remedy this if it is caused by blow by? My very mechanically inclined friend says it will.

 

The fuel is going from the cylinder to the crankcase. I guess a catch can might catch some of it, but I am not sure if it will make a huge difference. If you delete the PCV value, how are you venting the increased pressure? Are you just going to cause a bunch of seal leaks?

 

Thanks for the info.
Anyone using the fomoto value or even dipstick pump to speed up the oil change? If I skip the filter and only change filter once a year, then doing it from top is very tempting.

 

I change just the oil at 50% MM. I do that with the vacuum fluid extractor through the dipstick tube, it works great.

 

When I dont change oil filter, I can remove drain plug without lifting the car.
The oil change is very easy on RDX, I dont see a need for oil extractor

 

You might want to remove the drain plug after using the extractor, to verify that you got essentially all of the oil. When I did that on my wife's RDX, I found that there was too much oil left behind -- nearly 1 quart total between the pan and the filter.
Maybe my technique was at fault, but I have done this on other cars dozens of times.

On my VWs, maybe one ounce is left behind after using the extractor (and the oil filter is on top on my newest one, so no crawling).

I also change the oil at 50% MM on the RDX. So far, I have also changed the filter.

 

I know roughly how much oil is in the car based on the dipstick reading. I always check the dipstick before extracting or draining the oil and with the extractor I'm getting 95%+ out what draining would. I can feel the extraction tube hit the bottom of the pan, have to snake it in and out a few times to get down all the way. For me, it's good enough considering I'm doing that at 50%MM and then full drain and filter change at 5-10%MM. It's essentially doing 2x what the MM recommends.

 

A good oil filter is like $8 and should be changed at EVERY oil change, this whole every other idea is wild, Saw dudes up in this thread say ONCE A YEAR? WTF?!!
Doing an oil change at home with Mobil 1 and similar filter is like $35 and 30 minutes of work tops. Changing oil every 5k should be max IMO.

Also a catch can is a valid solution for this issue I see popping up via threads on here, not sure if anyone makes a direct "bolt on" oil catch can for this chassis but a universal one can be made to work as well. But blow by is a very common issue with Forced induction cars. and even worse on modified FI cars.

For my Integra I added baffles to the front of the VC and 10AN line to a little custom catch can(this is an old pic but the catch can setup is still the same)



I also have a Focus ST and have an aftermarket PCV plate with baffles and an aftermarket catch can setup, it collects a good amount of blow by, I don't drive that car a ton since I WFH and we take the RDX everywhere but I empty it like every few months and it has about 4-6 oz of fluid at a time in it.

 

Thanks for the info. Purchased a universal catch can (see below) from Evil Energy and my friend is going to mount it on the RDX for me. Hoping this helps and will also start changing oil every 5k miles max, instead of 7-8k miles like which is what the RDX is generally at when the oil life hits 20%. I'll let ya'll know how it goes after a few more oil changes.

Evil Energy Baffled Oil Catch Can, Oil Separator Catch Can 300mL
https://www.ievilenergy.com/products...atch-can-300ml

 

I mean the biggest thing for me would be the oil change interval with filter.

that catch can should work, depending on where the best point to mount it is, you might want to have him throw in a fumoto valve and drain line down to the slightly below the underbody covers so it’s easier to drain.

 

Does anyone have data from UOA to show that catch can reduces fuel dilution?
As far as changing oil filter every time…. I buy $12 Fram Endurance high efficiency rated for 25k miles. I think it can last for 7-8k miles. And no, its not important to get every last bit of oil when oil is changed every 4k miles.