Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 08, 2025 ...

Diesel fuel questions

January 20, 2018, 04:43:34 am

I have been driving a MBZ 300 SD diesels for 20 years now and I live in Kansas. I am guessing I go thru about 550 gallons of diesel fuel per year with only an tiny plastic inline primary filter that gets changed twice a year in addition to the robust secondary filter that that gets changed out every other year. That being said, I have never had a fuel issue, or any algae. i have never added any fuel conditioner, Is algae predominantly a problem in areas with high humidity?

Quote Selected

Re: Diesel fuel questions

Reply #1 – January 20, 2018, 07:49:57 am

All kerosene based fuels have water in suspension to some extent.  It becomes a problem when tanks are not serviced/cleaned at the supply point.  Then even with clean fuel it becomes an issue where tanks in motorhomes etc. are left for long periods with little use and condensation gets on the inside walls of the tanks via the vents.  That moisture eventually gets in the fuel and allows the algae to grow leading to supply line blockages and filter blockages and eventually corrosion within the tanks.

In your case with regular use the fuel is flushed through at regular intervals and does not sit.  Provided your supplier has clean tanks which they obviously seem to as you have no problems.  I also have driven diesel cars for many years with no issues but again they are in regular use and not parked for long periods.

With airplanes that have been stored for long periods and usually almost empty it is a big problem.  When they are required to fly again it is normal to find the algae and to treat all the tanks with "Biobor".  That in turn gets the algae loose so an engine run and one, or even more filter changes are done before flight. Also a big corrosion issue as most airplanes these days  have "wet" wings with no actual tanks inside.

Another issue is when the moisture in the kerosene based fuel gets cold and it turns to wax and again blocks the supply lines.  Airplanes have bypasses, with a warning light, on the filters, and the fuel passes through heaters to prevent this problem.  Or, why trucks keep the engine running in cold temperatures and use additives to prevent the waxing.
Speedbird 1.

Quote Selected

Re: Diesel fuel questions

Reply #2 – January 20, 2018, 10:24:24 am

High humidity really adds to the chances of getting algae in the tank. You can keep your fuel treated, polished, etc. but a bad load at a station ruins all that.  As far as the 300SD goes, the little $2 primary filter catches all the coarse stuff with the secondary doing most all of the work. Smart to change it out every couple of year as I have seen several where water collected in the bottom and rusted a pin hole in the steel filter and made a mess. Might be good to slice your secondary open when you change it to check for water in the bottom and see if there is any algae in the filter.  Our U300 has an OEM pressure cap on the tank that keeps most of the moisture out during daily temperature changes. The cap always gives a puff when removed for filling.                                                          I started my import/export business with MBZ diesels back in the '70s. I still have an '84 300SD with about 450,000 on with with absolutely nothing done to it except for oil and filter changes, batteries and brake pads. The OM617 5 cylinder is one of the best diesels ever made (if you change the oil). Starts instantly in subfreezing temps with a 5 second glow.

Pierce

Quote Selected

Re: Diesel fuel questions

Reply #3 – January 20, 2018, 06:55:03 pm

Thanks guys I think now I may want to add some as I doubt I will be burning two tankfuls per year while working.

Quote Selected