I finally put in my extra fuel filter and water separator. It is pouring here and I was under the truck for three hours. I remember there was a discussion about whether the fuel cap caused a vacuum in the tank or pressurized it. When I broke the fuel line at a union near the rear axle, when it came apart there was a huge sucking sound and no fuel dribbled out of the line. This is significant because last year I thought I had a bad batch of fuel so I broke the fuel line at the same point and drained 10 gallons in a very short time. The difference was then I had taken the fuel cap off. Someone on this site drilled a tiny hole in the cap to relieve what he thought was a vacuum situation and now I am going to do the same. One other scary thing. When I filled the new filter with diesel it wasn't near as slick as I am used to feeling and didn't smell as strong as usual. I wonder if it is the new low sulfur stuff? I will definitely be adding my WVO for extra lube (thanks for the inspiration QM)

Sucking not good in tank. Get new fuel cap. About $4/5 at NAPA. Cheap fuel system insurance.

Sucking not good in tank. Get new fuel cap. About $4/5 at NAPA. Cheap fuel system insurance.
It has always had that sucking sound when I took the cap off and this is my second one

"Diesel" cap?

Mine always sounds like is releasing pressure when I take the cap off to fill the tank. Is that a bad thing?

It will make a slight sound, but it's only a few inches of water column of vacuum - not a Hoover vacuum sound.

One other scary thing. When I filled the new filter with diesel it wasn't near as slick as I am used to feeling and didn't smell as strong as usual. I wonder if it is the new low sulfur stuff?
Your absolutely right about the low and now ultra-low sulfur diesel. It doesn't feel the same and it needs to be treated with some sort of lubricity additive. I've talked to a few shops in our area and in the states and everyone is noticing higher occurances of worn head and rotors, severely worn transfer pumps and several other parts that normally last much longer are getting worn out faster too. Kudos on the extra filtration stuff, but definitely need to add conditioner to every tank of fuel.

"Diesel" cap?

Both times I made sure I got the diesel cap and not the gas one. I may have done the wrong thing but I drilled a tiny hole at the top of where the cap is when it's screwed on. No sucking noise at all now. Now up to 25% added, filtered, WVO also. I'll let all you guys know how that turns out:cool:

What's the opacity of your WVO? light golden brown or dark?

Your absolutely right about the low and now ultra-low sulfur diesel. It doesn't feel the same and it needs to be treated with some sort of lubricity additive. I've talked to a few shops in our area and in the states and everyone is noticing higher occurances of worn head and rotors, severely worn transfer pumps and several other parts that normally last much longer are getting worn out faster too. Kudos on the extra filtration stuff, but definitely need to add conditioner to every tank of fuel.

One really safe thing to do is to mix with biodiesel, if it is available in your area. Biodiesel has a very high lubricity value, and mixes in any ratio with petroleum diesel. The 6.5 does not need any modification, unless for some reason you don't have synthetic rubber fuel lines. Only point of warning is that if your fuel system has a lot of gunk, you may need to change the fuel filter several times during the first few tanks, as biodiesel also has much higher solvent value and will strip off a lot of buildup. I ran two tanks of biodiesel through my Tahoe, one at 50% mixture, another at around 90%. When I changed my filter, there was a lot of gunk in it, but the fuel sure smelled better, and the inside of the fuel filter bowl was *pristine*!

Sincerely,

Rob

Even Stanadyne has approved Biodiesel as a lubricity additive, their tests were done with 10% and under mix, but I think they said 1-2% provides all the lubricity you need.

What's the opacity of your WVO? light golden brown or dark?
Sorry to take so long to answer QM, I was under the truck 3 hrs. today installing my new B&M deep tranny pan. My WVO, after filtering, looks kind of like honey. Not the real pale stuff but no where near as dark as the mixed stuff you showed in your thread about using yellow grease as an additive. Very happy so far):h

You can run more than 25% then. I was able to run more than 30% on the dark brown stuff before it started throwing optical codes and "dieseling".

You can run more than 25% then. I was able to run more than 30% on the dark brown stuff before it started throwing optical codes and "dieseling".
Thanks for the advice. It is VERY welcome and helpful:D