Crude based or synthetic oil ...

this whole conversation reminds me of people who talk about "don't run your tank out of gas, your fuel line will fill up with all the crud that collects at the bottom"

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.

not for this purpose it doesn't.

if left standing, it's already drained!

not unless the oil is ridiculously over-loaded that it's already allowing precipitation. in which case, you should be changing the oil more frequently.

then you will never observe whether the oil filer anti-drainback valves are working properly.

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.

indeed.

no they're not. and seal efficacy is not just a function of the seal material - it's design and also shaft finish quality.

regurgitation and failure to observe fact doesn't make for authoritative analysis. "sludge" does not close a sliding seal any more than gravel prevents your roof leaking.

what do you think a modern "synthetic" actually is? i'll tell you - it's simply a slightly more refined mineral oil than is traditional. and i know that for fact from a senior exec at one of the oil majors. modern "synthetic" is more a label for what the oil /doesn't/ contain than anything else.

most of the domestic "synthetics" are the same kind of group III mineral oils as mobil 1. so don't single it out as being any worse than the others. indeed, its additive package is very good.

at this point, it's not about the base, but the additives. premium "synthetics" contain premium additives. on that basis, and the fact that their additives permit sustained operation/longer drain intervals, they're worth the money. some even have better friction reduction which saves you their premium price in reduced gasoline consumption.

of course! but nerds are the people y'all rely on to get stuff done, so don't underrate them.

"Elmo P. Shagnasty" wrote in news: snipped-for-privacy@news.eternal-september.org:

Actually, running out of gas IS a bad idea these days. Not on account of any crud that might be in the tank, but bad for your catalytic converter.

SMS wrote in news:4f5795cb$0$11954 $ snipped-for-privacy@news.sonic.net:

Honda says the reason is primarily damage to the cat.

ummm....OK....which has nothing to do with the old wives' tale about low fuel causing "crud in the bottom of the tank to get sucked in"

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.

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 their automatics?

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 failure?

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.

to some extent, that's true. but there's a lot of detail missing in that broad brush picture. fact is, detergent isn't the only thing keeping the engine clean - it's what kind of viscosity improver [which breaks down over time and causes deposits], and what kind of base oil [which breaks down over time and causes deposits] too. even detergents are different from oil to oil, not to mention anti-oxidants, anti-foaming agents, extreme pressure additives, etc. so while paying a lot of money for a "boutique" oil doesn't guarantee high quality, /not/ paying definitely ensures you're going to get lower quality and thus will have to pay closer attention to the factory maintenance schedule.

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.

Ed

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

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.

Somewhere on teh intarwebs SMS wrote: [snip]

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.