Log Books and Pre-Buy inspections.

weirdjim said:
So in an engine that has a good oil filter (instead of the screen) why do we run "aviation" oil instead of some of the really good automotive oils that are on today's market?

Other than the obvious regulatory reasons.

Jim
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that's a very good question.

The engine manufacturers have antique thinking that the auto additive packages will cause a metallic ash to form in the combustion chamber, which could cause preignition.

That may have been true back in the day when we were allowed 5 gallon per hour oil usage in the big radials. But in today oil usage standards I don't believe it would do that.

That said, I don't think I'd like to see what will happen if you changed to a high detergent oil in any old Aircraft engine that is loaded up with crap that I see when I tear them down.
 
Tom-D said:
that's a very good question.

That said, I don't think I'd like to see what will happen if you changed to a high detergent oil in any old Aircraft engine that is loaded up with crap that I see when I tear them down.
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It would be really stupid to run a high-D oil in an old engine. You'd go through a dozen filters in the first hundred hours with dislodged crap. If somebody were to do this (heaven forfend that I'd know the person) they would run low or zero-D oil for a couple of hundred hours to SLOWLY purge the engine of accumulated crap and THEN keep it clean with moderate-D oil. No?

Jim
 
weirdjim said:
It would be really stupid to run a high-D oil in an old engine. You'd go through a dozen filters in the first hundred hours with dislodged crap. If somebody were to do this (heaven forfend that I'd know the person) they would run low or zero-D oil for a couple of hundred hours to SLOWLY purge the engine of accumulated crap and THEN keep it clean with moderate-D oil. No?

Jim
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Your "D" equals what? detergent? or Dispersant?

going from W80/100 an "A" oil, to a 20W50 "AD" oil is no problem.

changing from any "A" or "AD" oil to detergent oil is a big no,no. that will cause a catastrophic engine failure. specially in any old engine with a screen. Remember the filters have a by-pass, once clogged they pass all oil directly back to the engine oil system, then we have an engine with no filtration at all.
 
Tom-D said:
Your "D" equals what? detergent? or Dispersant?
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Detergent. So if a person with a high time engine chose to run a motor oil with no ashless or dispersent qualities with little to no detergent qualities it might work?

Jim
 
weirdjim said:
Detergent. So if a person with a high time engine chose to run a motor oil with no ashless or dispersent qualities with little to no detergent qualities it might work?

Jim
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I'm thinking it would.

plane ol 40 weight was all we had until they started calling it Ashless.
 
Tom-D said:
That's true.

The only reason you overhaul any in engine in part 91 is when you no longer trust it for any reason.

the engine on my shop floor at this time is being overhauled because of a prior failure of the crankcase thru bolts and the owner no longer trusted it, but it was running fine. He's overhauling it to save a .010" crank that can be used again with out regrinding which is not allowed beyond .010 under. so in this case we saved the crank which is a 4500-6000 buck item.
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Not just specific to this example, but the above is why I never trust engines with unknown backgrounds. I wouldn't know about that crank being at limits and plenty of pre-buys miss that kind of stuff. Of course if the owner sold it tomorrow he'd expect the value to be in line with a zero time overhaul and price it accordingly. I'd rather buy one run out and put a factory/large shop motor in that I know was done to new spec. This may be legal and a good deal for the owner, it would be a big disappointment as a buyer.

How many pilots do we all know that got a "good deal" on a bird with a low time motor and end up doing all kinds of work on it in the first year or two of ownership?
 
wabower said:
Snip.
]For these reasons, overhaul the engine at least every twelve (12) years, or on accumulation of the operating hours listed for the engine model.

For appraisal purposes, engines with more than 2x calendar limit are considered as run-out.
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Is this pretty consistent?
 
BillyBH said:
Is this pretty consistent?
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The guidelines established by the Aircraft Appraisers Association include this provision and the software is programmed accordingly.
 
BillyBH said:
If you rejected an airplane on the basis as too long between annuals based on calendar time, as suggested by manufacturer, youd pass on most of the GA fleet.
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Based on what I see out there I would pass on most the GA fleet :hairraise:
 
Skylane81E said:
Based on what I see out there I would pass on most the GA fleet :hairraise:
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I would guess there is a very low number of part 91 owner/operators that are compliant with the manufacturers requirements for service information.

How many operators do you know that have their aircraft serviced and lubricated IAW the MM ?
 
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