Archives

Just got my oil report back. 6% fuel in oil.


Has anybody else seen fuel in oil in a hypermiled diesel?

10k miles on oil
Rotella 5W40 (the old kind, pre-T6)
Some of the fuel used this tank was straight #2, but most tanks had a bit of bio. (5-15%)
My best guesses are:

1) injector(s) going or gone. This would be bad. I'd be looking at $2k in parts and at least a lost weekend. This generation of Duramax is infamous for injector problems that dump fuel in oil, but I guess I would have expected more than 6% if that were the case.

2) Light loads from hypermiling + cold temps all winter + a bit of bio = normal to expect some fuel in oil. Maybe I shouldn't expect 10k miles on oil under those conditions, even though many exceed that with ease in a duramax.

Is it as critical in a diesel? Don't they talk about a certain
amount of "lubricity" obtained from the fuel anyway, besides
the crankcase oil? Bio apparently does give some different
characteristics -- burns hotter, and if I understand what's been
said about furnaces tends to erode high-pressure parts a little
faster for some reason. Possibly including rings?
.
It could very well be that I have no idea what I'm talking about
here, somebody who knows set me straight..
.
_H*

I'd guess that it's #2. Do you do a lot of NICE-ON coasting? With the TDI, dilution sometimes seems related to situations where there's a lot of idling. That could be part of it, too.

Diesel fuel is much more oil-like than gasoline and does offer a good amount of lubricity. Biodiesel, even more so. But it's quite thin compared to motor oil, and I wouldn't want to let too much fuel contaminated oil get near a turbocharger with the heat and speeds that it's running at. Biodiesel will eat away at rubber, but I don't think it will erode metallic parts any faster if it's adequately filtered. High pressure fuel pumps frequently have lower wear when running good bio because of the better lubricity.

I'd guess that it's #2. Do you do a lot of NICE-On Coasting ?

yes.

I'd guess that it's #2. Do you do a lot of NICE-ON coasting? With the TDI, dilution sometimes seems related to situations where there's a lot of idling. That could be part of it, too.

Diesel fuel is much more oil-like than gasoline and does offer a good amount of lubricity. Biodiesel, even more so. But it's quite thin compared to motor oil, and I wouldn't want to let too much fuel contaminated oil get near a turbocharger with the heat and speeds that it's running at.

I agree....

Ah, it was probably the rubber bits I was thinking of, then.
I talked to a couple of heating oil companies starting to offer
bio mixes around here and the upshot was that even to run
something as high as B20 the wheezy ol' furnace would need its
share of upgrades, let alone for B100...
.
_H*