Regardless of the intervals, I always changed the filter. I didn't
like the idea of leaving old oil in the filter to mix with 4 quarts of
new oil. Dunno if you really save money but even if you did, I doubt
the amount of oil residing in an unchanged filter is small* compared to
the oil residing in oil galleries, the pump and the bottom of the oil
pan. "mixing" is completely unavoidable. any "extra" from the filter
is such a minimal percentage of the whole, it's insignificant.
* cheapo filters with defective anti-drainback valves can end up being
completely empty. if the anti-drainback valve works**, the amount of
retained oil can be higher, but it's still a negligible amount of the whole.
** most people "warm up" their car prior to an oil change so on removal,
the filter is always full. apart from not really being necessary these
days, this habit also serves to mask valve problems. [depending on
filter orientation of course] if you let the motor stand for an hour
before changing the oil, then remove the filter, you'll then find out if
the anti-drainback valve actually works or not. if the filter is empty,
On my previous cars where I could change oil myself without car lift, I
alway had to wait about an hour after engine shutoff so I would not burn
myself during oil change. Come to think of it, the oil filter was always
full with oil. But that was in the '90s and before. Maybe they used to
make better filters then.
And between 8oz and a pint will be hung-up in the upper reaches of the
engine and will not drain for you. "Better flow" won't help with that.
You wanna get as much oil as possible out of the engine? Leave it
overnight, then let it sit for 15 minutes after pulling the drain plug.
Bonuses to the above: Filter removal is mess-free, and the oil won't burn
You drain as much contaminants one way as the other. Unless the oil is so
old that it's saturated, all the contaminants are held in suspension with
the oil and will come out with the drain in any case. Contaminant-
suspension is one of the primary functions of oil.
the catalytic converter??? that's a new one - how's that supposed to be
affected by the fuel being a homogeneous mixture that gets drawn from
the bottom of the tank, not the top??? really, i'd love to read about
this technically challenging phenomenon.
how is that supposed to work? seriously, i'd love to read the cite.
and is it perchance written by the same honda analysis team that
misdiagnosed the "faulty thermostat" causing lockup clutch problems on
lol - this is indeed an old wives tale. the only "low fuel" condition
that could even vaguely influence pump life is "no fuel". and even that
is a mighty stretch, even if it weren't something most drivers carefully
avoid for other reasons.
My understanding of the concern that routinely running with low fuel in the
tank is as follows:
Electric fuel pumps are submerged in the fuel in the tank and cooled by the
surrounding fuel and the fuel that runs through the pump.
In the past, most pumps were designed to deliver fuel at a certain pressure
up to the maximum possible volume required by the engine. At lower engine
outputs (at idle, at cruise, putting around, etc.) the volume of fuel
delivered by the pump is far in excess of that actually used by the engine
and much of the fuel is returned to the pump via the return line.
Pumping excess fuel around heats the fuel (heat added by pumping, heat
added by running through the engine compartment, etc.).
When the tank is low on fuel, the heated fuel returning to the tank is a
significant percentage of the total fuel in the tank. Continually
recirculating (and heating) a relatively small volume of fuel raises the
overall temperture of the fuel in the tank significantly.
Since the fuel pump is only cooled by the fuel, continually running the pump
in a hotter environment can lower its life.
My feeling is that there was probably some truth to this 10/15 years ago.
Some newer vehicles use variable displacement pumps / variable speed pumps
that only deliver the needed volume of ruel and don't include a return line.
Therefore heating the fuel in the tankk won't be a problem. Even in cases
where the pumps still require a return line, manufacturer's know more and
the pumps are better. I doubt that running the fuel tank low continually is
much of a problem with new vehicles.
ok, let's examine this statement:
1. the fuel circulation from immersion is minimal. thus "cooling"
effect is minimal. that's assuming there's even anything to cool int he
first place - other motors like windshield wipers operate for hours on
end without cooling. why would any automotive designer run something so
critical so close to it's operating envelope that a known and expected
operation condition would challenge its integrity?
2. the fuel circulating inside the pump /does/ have the capacity to cool
significantly, because it's flowing. but again, why would any designer
want to take a chance on this stuff?
get a shop vac and put your hand over the nozzle when it's running.
does the motor slow down with the increased vacuum? or does it speed up
because it's now doing less work? answer that question and you'll
figure out that the fuel pump isn't working to "pump excess".
as for heat accumulation, again, what kind of designer is going to let
their product out the door if it can't handle 50-60°C? because that's
the most you're ever going to get from ambient under a hood. and even
120°C would not be much of a challenge.
that's just factless straw clutching - anyone saying that doesn't
understand the physics.
the only way it could have been a problem is if the pump relied of fuel
for bearing lubrication. [which is a fundamentally flawed concept in
the first place.] and even if it did, then the pump would have to be
run dry. drier than the engine would have already stopped at.
bottom line, this stuff is just presumption and nonsense. it's just
like the old days of microsoft circulating the story about how cosmic
radiation can flip bits in a chip, corrupt memory, and cause a crash.
and for years, people believed it. but then came linux, and the same
hardware stopped crashing. the truth was, microsoft software is buggy
sub-standard crap and it is their poor code that causes crashes.
similarly, pumps that fail are sub-standard crap. "cooling" as an
excuse for failure in the event of an entirely foreseeable and
expectable occurrence is just complete b.s.
1. who here has had a fuel pump fail?
2. who here has had a fuel pump fail and then sent it in for analysis to
determine the cause for real, as opposed to mere presumption?
3. better yet, who here has actually bothered to scope a pump /prior/ to
indeed. one pint is 1/7th of my drainable oil capacity.
if filer removal after being left standing /doesn't/ spill oil - and
we're talking b-series and d-series here, then the anti-drainback valve
is NOT working properly. honda filters are terrible for this. and that
you're experiencing this with your 3k mile change interval demonstrates
just how cruddy that domestic honda filter valve can be.
maybe. if it's one of the vertically mounted ones, mounted from the
top, of course it's going to be full. but if like honda or toyota, it's
horizontally mounted, or mounted at an angle, that's when you'll be able
to observe whether the anti-drainback valve works.
Heh! I thought I'd enter the details for my Honda and see what it said but
it only goes back to 1992! What about my 1985 AA 'City'*?
It's a good job that I have a supply of air filters, a couple of Gates
timing belts, front and rear wheel bearings, a couple sets of brake pads and
one of shoes for the rear, spare new dizzy cap and rotor (as well as a
couple used ones), a clutch, including pressure-plate (all new, boxed) and a
head-gasket set as none of these are available anymore from Honda or most of
the after-market folks (except for a rapidly-diminishing few).
Great little car, 198,000 kms on the clock, doesn't use oil between changes
and gets 55 miles per (imperial) gallon (46 US gallon) highway, 45 (38)
around town (and I don't exactly have a light foot). I've replaced all but
the headlights with LEDs, fitted LED DRLs and a high-stop brake light. Also
I've removed the back seats (to reduce weight) as I'm single and, after I'd
owned it for 18 months I realised I'd not 'unfolded' them (keep the weight
low and maximise cargo area) once. Really effortlessly quick between
intersections around town too, much faster than anything else on four wheels
other than someone 'racing'
A real pleasure to drive too compared with modern small hatches. Good
power-to-weight ratio and nimble and sure-footed. I wish I could afford to
get one professionally rebuilt, like people do with rare and expensive cars.
There's a little rust at the base of the A pillar that will require the
screen being removed to be cut out and patched. I wish I could find an
internet 'owners club' or similar, I'm sure there are tips and tricks
particular to the car that would be handy to know.
[*] Or Jazz, depending on where in the world you are
"Humans will have advanced a long, long, way when religious belief has a
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