Fuel Dilution of Engine Oil

I have to give lecture after lecture to senior management about the difference between vehicle electronics (built to last) and consumer electronics (built as cheap as possible). ECUs failing will be completely different mechanisms than PCs. Here is a short list of differences:
1) ECU Printed Circuit Boards are Conformally Coated to prevent moisture degradation for up to 30 years.
2) Components are derated for voltage, amperage, and temperature to ensure a 10 to 30 year component life
3) Only proven components (established reliability) from an established vendor are used. (This is a biggie.)
4) Heat Sinks are provided for every hot component. (Only the processor chip in a PC has a heat sink to prevent extremely rapid failure).
5) Connector contacts are gold plated (vs tin plate) for long life.

The list is MUCH longer than this, but the dozens of "ECUs" in you Boeing 7x7 and Airbus 3xx are incredibly reliable, so beware of using consumer PC failures as a basis for judging vehicle ECU electronic reliability.

 

This is a very good point, in fact the IPC inspection handbook for PCB assembly has 3 different inspection levels depending upon where the assembly is likely to be used - critical components where failure could mean death, high reliability components where failure is very inconvenient, and consumer electronics where almost anything goes.

[sarcasm alert] I'm being somewhat facetious with the last one, but its not that far off the mark [/sarcasm off]

At the place I used to work until last Oct., we generally tried to be at least somewhere between the first and the second, even though we really only needed to satisfy the second level.

I also wanted to comment on the paper that Jayman linked to on Pb-free solder: the test conditions were for bare Cu solder pads, but no one does this in industry that I'm aware of, normal practice is tin plate and some PCBs use Au plate. So the paper is interesting, but probably represents a worst case scenario.

 

While I understand that, I also recall experiencing an ECU failure in a vehicle once. Admittedly that was quite a while ago. Hopefully that doesn't mean I'm due for one on my next commercial flight... because that particular car and whatever aircraft I'll be on were probably built around the same time.

(I've also noted various threads about MFD troubles.)

 

You probably have run across hobbit's discovery of a ECU manufacturing error of first order. This accounts for a very large number of the Prius MFD problems.

Prius MFD

It's unusual for this type of bonehead to make it into production, but it did.

 

When you see a thread on the MFD issue, you can practically bet money on the car being a 2004 model. There was actually a design error that was then corrected sometime during the 2005 production year. Hobbit has a very interesting investigation and writeup on it.

Prius MFD

Dammit you beat me by that much.

 

We're starting to see a few MFD complaints from owners of 2006-2008 Prius, and it is unclear whether the root cause is a bad solder joint or a component failure.

 

I'd call that a design error. The surface-mount pads are not correct for that connector (or maybe the purchasing or manufacturing groups changed the connector type after the initial design was done without consulting with the designers?).

Concerning the original issue, it sounds like a good reason to change the oil every 5000 miles.

 

Absolutely a worst case scenario. However, various failure modes have popped up recently along similar issues

Although we probably had to transition to Pb-free solder, the industry as a whole very poorly understood what the transition entailed

 

You have my sympathy. In that situation, only heavy drinking works for me

It's erroneous to compare military/avionics hardware and software (They have much in common, neither system can fail) to automotive-grade hardware and software

When you apply such methods as CMM (Capability Maturity Model) to military-spec hardware, or aviation flight hardware (Fly by wire airliners are a good example), the standards are light years stricter. Production lots are subject to far more destructive testing, and rejection ratios are far higher

As an example, the Honeywell avionics suite in a modern fly-by-wire airliner actually runs separate sourced RTOS, so even a total failure of one RTOS should not impact critical flight safety. Even the large LCD display screens have replaced individual "boiler room" gauges, due to proven much higher dispatch reliability

However, the industry has gone through "gotcha" moments. For example, some Airbus A320 series sidestick controllers would partially fail, or generate spurious control inputs, due to dirt in the contacts. Some Boeing 777 roll issues were due to the control column sensors having similar dirt issues. The 777 doesn't use a sidestick like the Airbus, but the control column is fly-by-wire and has no direct connection to flight surfaces

Some Boeing 767 airliners had issues with loose connectors between the batteries and the power bus. Under certain conditions, the small arcing could result in corrosion, a very poor connection, and "noise" on the power bus. That tends to make the EICAS operate flaky or even fail, along with the autoflight.

A Martinair 767 flight from Holland to the US experienced rapidly deteoriating electrical problems until they declared an emergency near Logan airport. During landing and rollout, the thrust reverse failed to deploy, the antiskid and ground spoilers were dumped, and they skidded to a stop with all flat tires, some already on fire. Nobody was seriously hurt

So we still tend to make assumptions about system reliability, MTBF, but tend to be surprised by events that were not originally envisioned. For example, loose battery shunt connectors, dirt in contacts, etc. Aging wire on airliners is now a serious concern

 

I could tell you a very bad story about conversion to Pb free lead plating, but I'm forbidden from posting anything derogatory about my former employer under the terms of the NDA that I was required to sign to get my severance pay.

 

I find it interesting how some Prius exhibit fuel dilution, and others do not. The only way to know for sure, is used oil analysis.

If fuel dilution is excessive, conventional oil additive packages rapidly break down. Synthetic oils will also break down due to fuel dilution. If bad enough, even 5,000 mile intervals may be too long

 

Yep, I was thinking of them as well as the resolved issue. I haven't followed any of them closely, but had mentally noted them and was waiting for a pattern to emerge.

 

Actually what works wonders is to get the organization flying the planes involved in the engineering reviews. The pilots then tell the a program manager yapping about cost to shutup since "It's not your nice person on the line". I will drink to that.

 

Oh GAWD just do the heavy drinking. It's easier. Been there, done that, wrote a chapter in the manual

 

Are there examples of low-mileage Priuses with fuel dilution?

In fuel dilution cases, I wonder how many of them used extended oil change intervals before the dilution was noticed.

 

None of the analyses I've looked at showed problem fuel dilution, at least not by the definitions given. They don't seem to have dangerously thinned either. I'm not saying they were necessarily good either. However I was surprised that I didn't notice any2.5% or above--maybe I just missed them.

 

For the past 6700 miles I have been detecting fuel in my oil. My latest test is >5% dilution at 575 miles since change. I have changed my oil 5 times in the last 2300 miles all tests showing at least 1.8% dilution. My dealer says this is beyond them and they are unable to deal with it. Since I originally asked this question late in August I have removed the injecters, had them cleaned and checked and performed a 3M induction cleaning. I replaced the spark plugs also. My mileage is down about 15%. Any help here would be appreciated.

2004, driftwood, 42.5k, BC

 

Next up to check would be the O2 sensors, but I would expect an issue with those to throw a code.

What are your driving patterns like and do you do any long trips (30min+ highway)?

 

A dirty MAF can cause some of those symptoms, before a CEL is thrown