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#531042 - 12/15/05 02:03 AM TBN
MolaKule Offline

Registered: 06/05/02
Posts: 16361
Loc: Iowegia - USA
Can you have too high an alkaline reserve? I.E. can you use too high a TBN oil?


The Case of the Overbased Engine Oil:

A maintenance superintendent of a landfill gas burning power plant contacted us some time ago and asked about engine oil base numbers. He figured you can never have enough protection.

Q: Use of a higher base number (BN) oil if you can afford it. Is this a good way to maintain your engines?

A: No. You can actually destroy an engine solely by using a higher than needed base number engine lubricating oil. Total base number (TBN or BN) is a measure of the reserve alkalinity additive present in the oil. It is designed to neutralize harmful acids produced as the byproducts of engine blowby. What many engine owners don’t often realize is that the strength of this alkaline reserve package is tailored to the sulfur content in the fuel. It is not uncommon to see high levels of sulfur in large marine, landfill, or power generation applications, and as such high TBN oils must be used to combat the highly corrosive blowby gases entering the crankcase. Whereas most users understand and use the higher TBN oils for these sour fuels, if your sulfur content decreases, you must decrease your TBN number also. The following example illustrates the danger of not doing so.

Several years ago, a large reciprocating engine plant serving several Boston hospitals ran into this problem 1. The situation occurred when they were changing lubricants, and the suggestion at the time was to use a high detergency 24 TBN oil, even though their No. 6 fuel oil sulfur content remained at or below 0.5%. The cleaner blowby gases resulted in more alkaline reserve additives remaining in the oil. In the presence of water, these excess carbonates recrystallize to form larger particles, which in turn are carried to cylinder walls. A reaction with combustion gases occurs here, producing calcium sulfates. These products cling tenaciously to the cylinder walls, and look like a slate/stone like deposit (known as slating or furring). These deposits are very abrasive, and promote bore polishing, eventually leading to piston seizure.

The current efforts to use cleaner, low sulfur fuels nowadays means that engine owners need to consult their lube supplier when the fuel properties change substantially, so as to recommend the right matching lubricant. Make sure to analyze your engine oil properly on a frequent basis.


1: Seifert, W., Westcott, V. Santoro, S., “Systemic Evaluation- An Integrated Approach to Machine Condition Monitoring”, P/PM technology, Vol 5, Issue 1 pp 17.

From, the "Tribodetective Case Files"

#531043 - 12/15/05 07:09 AM Re: TBN
Bryanccfshr Offline

Registered: 10/09/04
Posts: 5416
Loc: Durango, Co
Thanks Mola. Would this indicate implications to those that use heavy duty industrial oil and or HDEO's(Not all fleet) in there clean burning gasoline vehicles?

#531044 - 12/15/05 07:59 PM Re: TBN
Steve S Offline

Registered: 01/20/03
Posts: 18449
Loc: East of IGO
I would like to add the tbn 24 oil would be a diesel oil where as for example Delo 400 is a heavy duty motor oil designed for both gas and diesel engines used in demanding commercial applications. I have 23 years experience working at an equipment dealership working on cars,pick ups ,big diesel trucks "Semis" tractors, forklifts,etc all run on hdeos ,these engines were clean inside and lasted with out any oil related problems.

#531045 - 12/16/05 01:25 AM Re: TBN
MolaKule Offline

Registered: 06/05/02
Posts: 16361
Loc: Iowegia - USA
The TBN in gasoline engines is usually limited to 12 or so, so HDEO or HDD oils are fine in them.

Unless your engine is running high sulfur fuels, you don't need a TBN over 14.

#531046 - 12/22/05 06:35 PM Re: TBN
Jaybird Offline

Registered: 07/08/05
Posts: 608
Loc: So. IN
In racing and motorcycle applications, frequent change intervals mean that these engines will theoretically see an elevated base during the duration of their useful life, as the fluids are not used long enough for the base to degrade as it does in passenger or industrial applications where OCI's are lengthy.

Considering the growing popularity of HDEO fluids in motorcycle and racing applications, and considering the increased amounts of h2o that high velocity racing tracts and off-road engines are subjected to, would there be benefits in chosing an oil with a lower virgin base number?

Could the detriments of this calcium sulfate be working against the pros of the add pack, competing for space, if you will?

#531047 - 12/22/05 10:43 PM Re: TBN
MolaKule Offline

Registered: 06/05/02
Posts: 16361
Loc: Iowegia - USA
In racing engines where oil is changed frequently, say after one, two or three races, the primary concern in terms of enhancement additives is providing plenty of anti-wear (AW) additives and antioxidants (AO). In racing engines, detergent and dispersant additives can be used at low treatement levels.

SO tbn in a racing oil can be 5.0 or lower.

#531048 - 12/25/05 03:43 PM Re: TBN
Titan Offline

Registered: 10/04/05
Posts: 2330
Loc: Mooresville, NC
Jaybird's comments on HDEO in Motorcycle applications applies to my Delo 400 in a V-twin has a shared transmission sump, and the shifting is SO much better with the Delo 400 than either the factory fill or Valvoline's Motorcycle 10-40. SO, I hope the Delo 400 is fine to run in this application.

#531049 - 07/31/07 12:24 AM Re: TBN [Re: Titan]
carlprop Offline

Registered: 08/08/04
Posts: 304
Loc: Placerville, CA
I know that this is an old topic I'm bringing to life, but I've never heard of a TBN of 24. It seems kind of high.
At the Signpost up ahead, your next stop, The Twilight Zone.

#531050 - 08/01/07 06:54 PM Re: TBN [Re: carlprop]
Steve S Offline

Registered: 01/20/03
Posts: 18449
Loc: East of IGO

I know that this is an old topic I'm bringing to life, but I've never heard of a TBN of 24. It seems kind of high.

Diesel oil
Why do people post I want the best for my car,,, When there isn't anything that is the best on the car to begin with.

#531051 - 08/03/07 11:48 AM Re: TBN [Re: Steve S]
bruce381 Offline

Registered: 06/23/05
Posts: 3327
Loc: Millbrae, CA
marine oils operate or did use high sulfur fuel something like 1-2% and needed high acid nutralizing properties.