russianDude

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

benromana

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.

russianDude

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?

benromana

No need, then.

Tachyon_flux

The sulfuric acid and viscosity are two separate issues.

benromana

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.

Tachyon_flux

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.

russianDude

I still change my oil every 4k miles.

russianDude

.