Diesel fuel conditioner with each fill-up?

[AiniA]

How many people add some form of conditioner with each fill? Any particular favourites or is it just snake oil? Talking about an ancient Volvo MD 11C here.

[tkeithlu]

Do your tanks have a history of breeding slime? Mine don't, and so far I have not found a need to add anything, despite using left-over fuel from before covid. The back-up generator at our emergency Operations Center is using fuel that went into the tank more than three years ago without issue. In addition, stability (as oposed to slime) is not as much of a problem with diesels as it is with outboards. The stuff is not volatile at room temperature,so you're not losing the part of the fuel necessary to ignition.

I think I'd wait for a demonstrated problem before investing in mouse milk, but your tanks might be such that you already have a problem.

[Bill O]

Originally Posted by AiniA

How many people add some form of conditioner with each fill? Any particular favourites or is it just snake oil? Talking about an ancient Volvo MD 11C here.

Most of the replies here will be additives to reduce water or funk in your tank(s). This is fine and will cover a large majority of diesel problems.

The issue w/older diesels running the ultra low sulfur fuel is the lower lubricity in these fuels. For an older motor this would be up on my top list of additives to every fill. Also doesn't hurt to add a cetane booster w/with a cleaner for the injectors. I use Power Service Diesel Kleen (+cetane boost) in our older Perkins 4.236 and seems to work well. It basically has all 3 items (lubricity, cetane and cleaner) in 1 product, so less products to purchase.

[Calif.Ted]

Valvtech fuel and I add cetane booster, no smoke noticeable on start-up.

[AiniA]

Originally Posted by tkeithlu

Do your tanks have a history of breeding slime? Mine don't, and so far I have not found a need to add anything, despite using left-over fuel from before covid. The back-up generator at our emergency Operations Center is using fuel that went into the tank more than three years ago without issue. In addition, stability (as oposed to slime) is not as much of a problem with diesels as it is with outboards. The stuff is not volatile at room temperature,so you're not losing the part of the fuel necessary to ignition.

I think I'd wait for a demonstrated problem before investing in mouse milk, but your tanks might be such that you already have a problem.

Bought the boat just before the end of the season. Checking/cleaning the tank is on the list.

[Rapanui]

We had a pre-existing diesel bug problem when we took our boat out of charter with globules of slime in the primary Racor filters. We used Marine 16 Complete to shock the system, which came out best in a UK sailing magazine review and allegedly not only prevents the bug but improves cetane, provides lubrocity etc. It stopped the bug and with regular maintenance use at fills, has kept us bug free and the fuel clean without having to clean the tank or have the fuel cleaned.

[Lepke]

I've been on the water with my own boat since 1961. Private and commercial vessels. I always use a conditioner and never had a fuel problem. I use Archoil Ar6500 and previously used Ar6200. Both stabilize fuel for a year+, cleans the fuel system, increases cetane, increases lubricity, and kill the bugs. Ar6500 gives a better mileage boost. Bot cost about 10¢ a gallon to treat. With 6200 I got about a 6% mileage boost, 6500 gives about 10% better than no treatment. So I pay about 10¢ a gallon for a 10% mileage gain along with the other benefits. I have Detroits with mechanical injectors and haven't changed one since 2011. Last time I opened tanks, there was no sludge, water, or debris. I use a 2 micron primary.

Available at archoil.com, Amazon, or ebay.

[team karst]

Originally Posted by Lepke

I've been on the water with my own boat since 1961. Private and commercial vessels. I always use a conditioner and never had a fuel problem. I use Archoil Ar6500 and previously used Ar6200. Both stabilize fuel for a year+, cleans the fuel system, increases cetane, increases lubricity, and kill the bugs. Ar6500 gives a better mileage boost. Bot cost about 10¢ a gallon to treat. With 6200 I got about a 6% mileage boost, 6500 gives about 10% better than no treatment. So I pay about 10¢ a gallon for a 10% mileage gain along with the other benefits. I have Detroits with mechanical injectors and haven't changed one since 2011. Last time I opened tanks, there was no sludge, water, or debris. I use a 2 micron primary.

Available at archoil.com, Amazon, or ebay.

Good to know, but…Will it work in Florida? [emoji848]. Lots of weird stuff grows here.

[Startracker]

Originally Posted by AiniA

How many people add some form of conditioner with each fill? Any particular favourites or is it just snake oil? Talking about an ancient Volvo MD 11C here.

Important for old motors with the new ULSD diesels I feel. I run Howes. Why Howes?
1. It is available everywhere.
2. The cost is reasonable.
3. It smells nice, I fill my filter housing when changing the filter cartridge. Smells much nicer if you spill a little in an awkward location, and giving the injectors a good blast of it seems to be just fine.

For what it's worth, another person I know who runs a heavy equipment repair place, simply filters used motor oil @ 5 micron and adds about 30% of that. He feels he gets the lubricity and other benefits, plus a reduction of 30% of his expenses for fuel. YMMV of course.