Determining oil change intervals via analysis

[Matt Whiting]

rmac wrote:

http://www.autoblog.com/2006/08/02/determining-oil-change-intervals-via-analysis/

Interesting how some people spend $30 for an oil analysis in order to avoid a $20 oil change. hmmmm.

you're not "avoiding an oil change", you're getting a checkup on the health of the engine. chemical content tells you a lot about how the motor is running, too hot, too cold, contamination, wear, imminent failures, etc. if you could predict whether the motor was going to fail in the next 6 months, and you were planning a major road trip, would you just go anyway and get the car fixed along the way, or would you get it done now while you have the time and resources to do the job properly? you don't wait for a plane's engine to fail in flight [if you can avoid it!] do you?

With a car, sure I'd just keep on driving it. Oil analysis can't predict with any certainty when an engine will fail. In a airplane, I'd have it torn down and inspected. However, this is much easier than with most cars. A good aircraft mechanic can rebuild the top end of an airplane engine in the time the car mechanic is getting the accessories removed from a modern car.

To rebuild a small airplane engine costs about $20,000 and takes months. You don't want to do it unless you have good evidence that it is needed.

I was talking a top-end. That can be done in two days tops. And a full overhaul doesn't take months. Where'd you get that? A good mechanic do do that in 3 days. And many folks get a factory reman and that takes about two days to do the engine swap.

Matt

 

[Guest]

To rebuild a small airplane engine costs about $20,000 and takes months. You don't want to do it unless you have good evidence that it is needed.

I was of the impression that a major overhaul was mandated at so many hours running time.. Was it 5,000 hours, or more?

 

[Stubby]

I was of the impression that a major overhaul was mandated at so many hours running time.. Was it 5,000 hours, or more?

2000 hours is a typical number. But so what? I would certainly have an oil test done within the first hour on a new or rebuilt engine.

 

[Guest]

2000 hours is a typical number. But so what? I would certainly have an oil test done within the first hour on a new or rebuilt engine.

I am sure you would.

 

[Matt Whiting]

I was of the impression that a major overhaul was mandated at so many hours running time.. Was it 5,000 hours, or more?

Only if the aircraft is used commercially. The typical TBOs are 1500 - 2000 hours.

Matt

 

[The Ghost of General Lee]

Well, perhaps you regard ignorance and stubborness as virtues, but I don't. It never ceases to amaze me that people can look at scientific data that refutes their beliefs and just dismiss it because they don't like it. It takes all kinds, I guess...

Faith based car maintenance?

 

[JS]

To rebuild a small airplane engine costs about $20,000 and takes months. You don't want to do it unless you have good evidence that it is needed.

Hah. That all depends on how deep your pockets are. I've seen an engine exchange ($$$$$$) in a commercially-owned single-engine tri-tail bonanza. Total downtime was 3 days, but they prolly spent $25k on the job in the mid 90s.

The biggest issue with general aviation aircraft is they're still using 100% manual engine controls. While our cars have advanced greatly in engine management, airplanes are still dicking around with mixture and carb heat knobs. All it takes is one descent with the mixture knob out to destroy an engine. Or you run overrich and get crappy economy and clogged up sparkplugs.

JS

 

[jim beam]

Faith based car maintenance?

sure! beats bothering to actually learn anything.

 

[JS]

In my neck of the woods, air filters need to be replaced only once every two years or so; they don't get dirty enough to warrant replacement before then. I had replaced mine in Jan 2005 and wasn't due for a replacement for another 8 months or so.

Once a year here, sometimes twice. Pine pollen season clogs them up noticeably every time. Sometimes hay season can do it, too.

On my dodge truck, OTOH, which spends time on sand/silt roads and has the worlds crappiest air intake design ever (it sucks air right off the passenger wheel), its about 3x a year and I put about 1/3rd as many miles on it.

JS

 

[Jim Warman]

So... I take it nobody has seen that this cross posting bastuhd hasn't replied to his thread????

"I'll have spam. spam. spam, spam, baked beans and spam"....

 

[Matt Whiting]

Hah. That all depends on how deep your pockets are. I've seen an engine exchange ($$$$$$) in a commercially-owned single-engine tri-tail bonanza. Total downtime was 3 days, but they prolly spent $25k on the job in the mid 90s.

The biggest issue with general aviation aircraft is they're still using 100% manual engine controls. While our cars have advanced greatly in engine management, airplanes are still dicking around with mixture and carb heat knobs. All it takes is one descent with the mixture knob out to destroy an engine. Or you run overrich and get crappy economy and clogged up sparkplugs.

Not all airplanes. Check out Cirrus and other new designs.

Matt

 

[Brian Nystrom]

True, but during the warranty period it is the manufacturers that need to be convinced. I'd change my Hyundai oil at 10K miles if I wasn't worried about voiding the warranty. And with the 100K warranty, it means I can't start my 10K intervals for a long time.

Agreed. I was referring more to the people who are absolutely convinced that they must change their oil more frequently than the recommended 7500 mile intervals.

 

[Guest]

So... I take it nobody has seen that this cross posting bastuhd hasn't replied to his thread????

Makes me wonder what the ulterior motive was behind the original post.

 

[Elmo P. Shagnasty]

I was referring more to the people who are absolutely convinced that they must change their oil more frequently than the recommended 7500 mile intervals.

"must"? No.

"Cheap insurance"? ABSOLUTELY. There is no cheaper insurance for an engine than oil changes.

Figure out how much you want to pay for that insurance, and set your intervals accordingly.

If you want to keep the car a long, long time, then 3K intervals (or even 5K if you bought the car new and are using good oil) are extremely cheap yet very effective insurance.

 

[Guest]

Well, perhaps you regard ignorance and stubborness as virtues, but I don't. It never ceases to amaze me that people can look at scientific data that refutes their beliefs and just dismiss it because they don't like it. It takes all kinds, I guess...

No, I dont regard ignorance and stubbornness as virtues. There are a lot of people who are impressed by apparently highly technical data and specifications, and who really dont know what, if anything, it means.

 

[Bob Adkins]

The big value of doing an occassional oil analysis is to catch mechanical problems when they are small and before more damage is done.

On every change, put a drop of oil on a piece of glass and check it under a $2 10x eye loupe in strong light. You can easily see metal fines in the oil, most of which are normal. You can determine if they're ferrous or non-ferrous by passing a magnet underneath the oil drop. If you see larger particles than normal, better get it checked out.

I'm guessing that antifreeze can be detected in oil with a $5 dollar black light in a darkened room.

 

[Bob Adkins]

No, I dont regard ignorance and stubbornness as virtues. There are a lot of people who are impressed by apparently highly technical data and specifications, and who really dont know what, if anything, it means.

You would be surprised how easy it is to learn what the data means.

That said, it isn't worth it. It's cheaper just to change the oil.

 

[Bob Adkins]

"must"? No.

"Cheap insurance"? ABSOLUTELY. There is no cheaper insurance for an engine than oil changes.

You're right to a point.

However, engine failures are seldom directly oil-related. An engine usually fails from part failure or abuse long before they wear out from infrequent oil changes. By the time you start to see oil-related wear, a car is usually very old, and has over 150K miles on it.

Rather than worrying about 3000 mile or 5000 mile oil changes, I worry about things that happen suddenly, such as cooling system failure, cracked block or heads, broken timing chain or belt, punctured oil pan, broken valves, etc.

 

[Elmo P. Shagnasty]

"Cheap insurance"? ABSOLUTELY. There is no cheaper insurance for an engine than oil changes.

You're right to a point.

However, engine failures are seldom directly oil-related. An engine usually fails from part failure or abuse long before they wear out from infrequent oil changes.[/QUOTE]

Well, but parts can easily fail due to infrequent oil changes.

Yes, parts can also fail independent of that. That's why all insurance is a gamble....but I reduce my gamble by buying a Honda, Acura, Toyota, or Lexus.

 

[Matt Whiting]

"must"? No.

"Cheap insurance"? ABSOLUTELY. There is no cheaper insurance for an engine than oil changes.

But it is wasted money, no matter how cheap. And with synthetic oil it isn't all that cheap.

Figure out how much you want to pay for that insurance, and set your intervals accordingly.

I prefer to not pay for things I don't need. I change at 5K miles now because it is easy to remember. I change at 10K when the warranty runs out.

If you want to keep the car a long, long time, then 3K intervals (or even 5K if you bought the car new and are using good oil) are extremely cheap yet very effective insurance.

I keep my cars a long, long time at 5K and 10K intervals. My minivan had 178,000 when it was totaled and it was doing fine on 10K changes. The reality is that you have absolutely no evidence that more frequent changes extend engine life, because no such evidence exists, unfortunately. I've looked for years.

We call make decisions that make us comfortable, but none are based on data.

Matt