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#469730 - 03/13/05 10:38 PM discussion on 'ash' content in oil
rokky Offline

Registered: 03/11/05
Posts: 244
Loc: Canada
I have been researching ash content in motor oil and what it means to motorcycle engines and engines in general. There seems to be some conflicting information out there and no real definitive answers.

Many of us use or want to use diesel engine oils in our bikes due to better specifications and price when compared to car and motorcycle specific oils. Diesel oils have many qualities well suited to motorcycle engines. Neither types have catalytic converters or much in the way of emission control except for, perhaps, California bikes.

Ash content is proportional to the detergent levels in oil. Some ash content can be contributed as a by product of the oil base itself but mostly from the detergents present. Ash is said to plug up c. converters in time.

Diesel engines produce much more engine deposits due to the fuel and the sulphur content in the fuel. High detergent levels are necessary. Diesel engines need to run longer between oil changes due to downtime and costs.

Is this ash content harmful for bikes?

One oil expert said that low ash promotes longer valve life with no real data to back up the claim. I have also read that ash cushions the valve seats during combustion promoting longer valve life.

Ash is a by product of combustion and is bound to cause more combustion chamber deposits. This may be a concern for old engines that do have more oil getting into the combustion chamber due to worn rings and/or worn valve seats and guides. I would not think to be a concern for engines in prime condition.

High ash oils can have better TBN numbers. High TBN numbers are indictive of oils that will neutralize acids, water, oxidation processes, and combustion by products better and longer. These high ash oils should be better for 'extended drain'.

The preceding paragraph holds true for Group 1,2,and 3 oils. It does not hold true for Group 4 and 5 oils which are able to achieve high TBN without high ash.

So. What is the answer? Is ash good? Is it bad? What levels of ash would be acceptable and what would be unacceptable?

We could just use the Group 4 and 5 synthetics and not even worry about the ash.

I invite your comments.

#469731 - 03/13/05 11:44 PM Re: discussion on 'ash' content in oil
fuel tanker man Offline

Registered: 08/04/04
Posts: 1347
Loc: wytheville, va
Here are some of my opinions... since you asked. [Smile]

I have decided to move away from synthetic in my '94 Harley Davidson (Evolution engine) for the following reasons:

1) The cost of a decent synthetic is getting too darned high; I had been using Mobil 1 "redcap" 15W50 but they've changed the formula and raised the price.

2) Dino oils are better than ever. [Smile]

3) The UOA's at this forum, if read and understood collectively, show no advantage whatsoever to running synthetic oils. In the cases where wear is not identical, it's actually common to see the dino beat the syn in that department--and low wear #'s are the "be all end all"--in the end. [Smile]

4) In a motorcycle engine you're likely going to be dealing with either a sump common to the tranny and the engine, and/or an air cooled engine which likes to run on the hot side. And more fuel dilution issues on some models. And probably a higher tendency for the oil to collect "garbage" from the by-products of combustion. For this reason, quick drains are important. I have decided (remember that we're talking about my opinion here) that it's too risky to leave an oil in for more than 2500 miles on a road bike. I will probably change mine out at 2000 miles to be on the safe side. Again, issues of fuel dilution and other contaminant build up in the oil are too prevalent in these engines to go for a long drain interval--so why use synthetic?

4) For the issues mentioned in #3 above, it is not cost effective to run a synthetic oil--in order to justify the price, you've got to extend the drain. And if you extend the drain, you may be running a fouled oil; the only way to be sure is with a 20 dollar UOA. (Which defeats its own purpose).

5) The only real advantages to synthetic oil would then be its superior ability to stay in grade, and its ability to avoid baking into a paste if you over-heat your engine. (Notwithstanding the fact that if your engine ever gets that hot it's toast anyway! [Big Grin] ) However--with quick OCI's using the newer dino oils, neither of these concerns are real enough to merit the extra expense of the syn.

But I know you asked about ash...

I think it's probably a non-issue. I'd be more concerned with TBN and viscosity retention than with the ash content. If ash was a "clear cut" concern, there wouldn't be so much conflicting information out there I wouldn't think.

If you can run a 15W40, I say go for the HDEO--it'll serve you well, I feel sure.

I wish Chevron made Delo in 20W50. They do make a straight 50 weight Delo which would probably be robust as all get out, but not so good in cold weather. [Frown] So we compromise. My HD calls for a 20W50, and I believe I've found the best 20W50 dino on the market in Havoline. It's still got the zinc/phos package pretty well intact, and the flash point is 492--better than some synthetics of that same weight class.

I do plan on a UOA of the Havoline this spring, after I've put a couple thousand miles on it.


#469732 - 03/14/05 12:50 AM Re: discussion on 'ash' content in oil
rokky Offline

Registered: 03/11/05
Posts: 244
Loc: Canada
Your post is not opinionated at all.

Very factual and all you say makes good sense.


#469733 - 03/14/05 01:25 AM Re: discussion on 'ash' content in oil
427Z06 Offline

Registered: 12/06/03
Posts: 7409
Loc: Austin, TX