Saturday, September 23, 2023


Ask Dave: Should I use fuel additives for my Cat diesel?

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses Cat diesel engines.

Dear Dave,
I have a 2005 Fleetwood Providence 39L with a 350 Cat diesel engine with 60,000 miles on it. Should I be using a diesel additive or is diesel fuel good enough to protect my engine? If so, what brand would you suggest is best? —Ardo

Dear Ardo,
From what I have gotten from most of the diesel technicians and looking at the Cat owner’s manual they do not recommend any type of additive. Their engine is designed to run on high Sulphur Diesel. What is important is to service the engine regularly and only use Cat-approved filters and oil – especially the ultrahigh efficiency fuel filter.

I have seen several posts and talked with my Winnebago rep. They stated they use Power Service Diesel Additive. I have used that in several Chevy 3500 trucks with the Duramax and put more than 250,000 on three different vehicles.

One other thing that I believe is important is to only use top-tier fuel and make sure it’s the blend designed for your temperatures. We did run into some issues with driver’s filling up in the South and hitting cold weather coming back home to the North. But sometimes you can’t tell or can’t help hitting colder weather.

Check your Cat manual to see if there is any recommendation there as well. I will also keep checking to see if I can find a Cat technician, although that is harder these days as they are not in the RV market anymore.

One more update. I was able to get in touch with a Caterpillar technician in the on-highway division. He said they do not recommend any type of additive other than Power Service anti-gel in cold weather. Plus, he recommended larger truck stops for fuel as they cycle diesel faster and their engines can handle up to B30 biodiesel.

And yes, even though the box says “Fuel Supplement,” it is an anti-gel product.

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


  1. I have had an eye opening education on diesel fuel over the past week and realized I had an incorrect description of the recommendation as High Sulfur diesel in the article. My technical source at CAT stated they recommend the higher sulfur diesel but after several comments such as yours, I found out that there are different grades of diesel fuel for various applications.My CAT tech contact was not an RV technician and I’m sure his definition of High Sulfur was for construction equipment

    In 2006, the government started a program to reduce the sulfur content in diesel fuel as it was an air pollutant. Today you can buy Low Sulfur Diesel and Ultra Low Sulfur Diesel fuel. The Low Sulfur Diesel can only be used for off road applications such as farming, construction, and “Reefer’s” on the big rigs. This fuel can not be used on over the road vehicles but can be purchased at fuel stations as #1 Diesel. Sorry for the slip.

  2. I see others have spotted the hi sulfur part of Daves post. Many diesel owners have been using additives to combat the reduction of sulfur . Sulfur like lead in gasoline acts as a lubricant. Fuel pressures in Diesel engines run 25,000-40,000 psi which I find amazing. Fuel pump problems surfaced with the reduction of sulfur & many owners feel the need to use additives.Cummins does recommend power service conditioner or at least did a couple years ago.

  3. Cat uses a HIGH SULFUR fuel. I don’t think so. Probably cant even buy that stuff.
    All pumps I see are 15ppm lo w or ultra low sukfur

    • Totally agree, sometimes I wonder who actually writes Dave’s replies! I believe he needs to retract that statement!

      • In 2005 Low Sulfur diesel was not required. That is why CATS owners manual calls for high sulphuric diesel. Reading further CAT rep says they can use up to B30 biodiesel which helps replace the sulphur content.

    • Most of the high sulfur diesel pumps that I have encountered are marked as “OFF ROAD ONLY” and are a dyed fuel of which I use for my farm tractor. Filters used must meet or exceed manufactures standards but you are not required to use their filters in accordance with the “Hatch Act” which makes it illegal for them to demand such. They will NOT put this in writing.


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