In 1985 I purchased a brand new a Daihatsu Rocky, 2.8 NA diesel. I used it mainly for highway work, but as I was working as a farm salesman needed a car with clearance and sometimes 4WD to get over rural properties. At 24,000kms I fitted “dunny roll” canister filters. One for in the fuel line for fuel and one, a by pass filter for the engine through a T piece in the pressure line and a return to the sump direct via a hole knocked in the side of the sump. I had the sump oil analysed continuously, approx each 6 months (about 20,000kms) for the rest of the time I had the vehicle. I sold it with 360,000 kms on the clock. The oil analysis was done at Wigmores in Perth who had the Caterpillar franchise for WA back then. All analyses were well within spec. I am no expert about these things, but the reports and my tame mechanic told me so, and I did get to understand them more over time. From the time I fitted the by pass oil filter I never changed the sump oil at all, just left it in there. I changed the dunny roll every 1200-1500kms, took 5 minutes, and added oil back to replace what was lost with the dunny roll, this was between 500ml and a litre, each time I forget now.

To the query you have – “when do I know when to change my dunny roll filter?” It’s easy, pull the dipstick, wipe engine oil on the palm of your hand (about 2 drops) and smear it into your skin, wipe it off with a clean tissue. If your palm is clean the filter is not blocked, if black remains in your pores the filter needs changing. A few times of this and you soon work out when it needs to be changed and dont need to get your hand dirty, except to brag to mates. In my case it was “up to 2000 kms”, but as dunny rolls were only 50 cents each back then I decided to change them earlier. If it ran over for some reason, say up to 3000 kms or more I would then change the dunny roll after a short run, say 500kms, and voila, a clean palm.

After fitting the fuel filter I never replaced the Daihatsu fuel filter again – why would you at $80 a throw versus 50 cents.

This car never burnt oil or had any premature wear at the time of sale. In fact the only things I ever did was replace a bolt on the power steering, and a new radiator due to the rainwater I was using (I lived on a farm) reacting with the radiator as it was caught off a zincalume shed roof. It also stuffed the truck radiator and the old farm 4wd too.

I hope this is of interest to you. I notice the 1HZ we have has very black oil, as did the Rocky, and a Case tractor I had. I haven’t fitted dunny roll filters to the Landcruiser because we are unlikely to do enough kms to wear it out while we have it (we are retired) to tow our Tvan around. More than 160,000kms travelling around Oz is just not going to happen, and also we live in town now and having dirty dunny roll filters to dispose of would be a hassle, plus I now have clean hands and can barely handle the smell of diesel on them nowadays – so things have changed.

I was very interested to note from your work that the OEM filter has the finer filter in it, so that may explain why some 1HZs do a lot of kms before wearing significantly.

Further, my cousin used these filters on his Deutz farm tractors, and had a similar experience. A small fault in one engine had it pulled apart at 5000 hours, and the mechanic couldn’t belive how clean it was inside. My cousin also had a tractor stop through lack of fuel. The issue was water had got into the fuel tank and the dunny roll filter blocked rather than let any water through.

Hope you find this “interesting” Paul

Cheers
David