# 4.6 Motor Question

Fordfan wrote:

Or how about a low oil level indicator. True story: A long time customer had an early 70s Buick. Very well maintained, high mileage. As was common on Buick engines of that vintage, the oil pump was weak and the oil lamp would flicker at idle on hot days. He gave the car to his 30ish yo son. After a few weeks, the son brings the car in pouring oil from every opening and barely running. I drained 7 gallons of oil out of that engine! When the oil light would flicker, he would add a quart or 2 of oil. He "estimated" 2 quarts at a time by the amount of oil running down his driveway!! The father was such a smart man and well informed customer, he was a retired Steelworker. The son had a Masters in Electrical Engineering. Go figure!
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my sister added some oil whenever the idiot light came on.
They are not that hard to read.
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Don't drink water, fish have sex in it!

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wrote:

What makes you think she would have done any different with a gauge?? Very possibly she would not have noticed the problem at all with a gauge. At least with a light there's something bright and shiny to attract their attention.

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A go/no go gauge is exactly what it is. It is a positive indicator. If you only have the light, you only have a negative indicator. The light might not be on because the oil pressure is good, but it might also might not be on because the light circuit is bad. With the go/no go type gauge you have a positive indication that you have sufficient pressure. If the gauge doesn't come up to pressure it might be because you have no pressure, or it might be because the gauge circuit is bad, but either way you know something is wrong.
As for indicating trends - you seem to be very attentive and understand the reasons for oil pressure fluctuations. What percentage of car owners do you think that applies to?

Well you sound like a really attentive vehicle owner. Now for the big question - has all this attention to changing oil pressure made any significant difference? Have you saved an engine because you saw the oil pressure slowly decreasing over time? For me, I've never had an oil related failure of any kind. My oldest "vehicle" is a 1981 Ford 7710 Tractor. It just turned over 6000 hours (rated speed for the hour meter is 1900 rpm). It only has an oil pressure warning light. I've never really worried that it doesn't have a gauge. One of my newer tractors has a oil pressure gauge, but it isn't calibrated. It is backed up by both a light and a warning horn (plus a failure will display STOP on the main dash display). The gauge is just a bar graph thing that has no values. It is totally worthless, but it does change over time. On a hot day when you work the tractor hard, it reads lower than on a cool day when you are putting around. Over the years, it has trended lower. But so what? What should I do as a result of the entirely predictable changes? Nothing is what I've done. The gauge has been no more useful than just the warning light on the other tractor.
Ed
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C. E. White wrote:

Oil pressure trending lower over many years usually just means normal main bearing and crank wear, but dropping in days or even hours could be a blown head gasket or failing oil pump. In one of those situations, by the time the idiot light comes on or the fake gauge SUDDENLY drops to zero, it's time for a new engine.
The same three vehicles I've had for many years: 1990 Lincoln Mark VII - 158.9K miles 1994 Lincoln Mark VIII - 109.8K miles 1990 Toyota Truck - 237.8K miles A combined total of over 1/2 million miles with 10K oil changes and ZERO internal engine problems on any of the vehicles.
I did have the idiot light on the Mark VIII turn on once at 70 mph, but the OP gauge was showing a steady 60 psi, so I just kept going. When I got the car up on ramps at home, I found it was the factory oil pressure snap switch that had failed; without the real OP gauge, I would have been really inconvenienced out there on I-35 at 2 AM, so Ill just keep running with OP gauges in all my vehicles.
I also have voltmeter gauges on all my vehicles, since I dont trust the other idiot light for the charging system either. :)
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And how often does this happen? I've had a couple of head gaskets fail in my life, and both times the first symptom was overheating. I suppose you can get a massive oil leak, but a massive coolant leak seems more likely. And even when oil pumps were driven off the distributor gear, gradual failures were uncommon. With todays crank driven pumps, it is much more likely that an oil pump failure will be sudden and in that case the light is as good as a gauge.

I haven't had any sort of significant engine failure in over 20 years. The last time I had one was a 1978 Fiesta with a 140,000 miles. I managed to burn a piston (clogged EGR, and drving flat out for 35 miles). I have a 35 year old Dodge dump truck with an unknow number of miles (well over 100,000). The only thing that has failed in the oil system is the crappy electric oil pressure gauge.

For you it seems like a reasonable thing. You understand what gauge movements mean and you pay attention to the gauges. I am suggesting that you are the exception. Most vehicle owners don't pay attention to the gauges, and when they do, they often misinterpert them. It must really upset you that car makers are now installing computer controlled temperature gauges. The gauges appear to move like old style gauges, but actually the needle position is determined by the PCM and not the water temperature. Both my current Nissan and Fords have this sort of gauge. They are not completely go/no go gauges, more a sort of incremental gauge with the position dictated by the PCM.

I am surprised you don't have an old style ammeter. Voltage meters are OK, but to be truly useful they need to be calibrated. The OEM ones just have a few poorly located markings and by the time you figure the voltage is too low, it can be too late. Even with the poor quality OEM gauges, if you pay careful attention to the position of the needle you can determine that it is lower than normal, but again this is only useful for people who pay attention and understand what voltage gauge movements imply.
Most OEM gaguges are just for looks. They aren't particularly well calibrated and in many cases aren't direct reading gauges. It used to be that the Germans actually included calibrated gauges, but it has been a couple of decades since I owned a German car. I have no idea what the Germans are doing these days. In recent years I have owned Japanese and Domestic cars that use non-calibrated, poorly marked gauges that are no better than go/no go indicators.
Ed
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Ed White wrote:

No way that I'm putting an ammeter into a Ford product, since they tend to burst into flame quite well without the "outside help" of an aftermarket ammeter install. In any event, a voltmeter is much more useful than an ammeter, and WAY safer, per this article: http://www.egauges.com/ATM_Tips.asp?TipPage=voltmeterammeter.htm
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I agree with the major points of the article. If you have a good voltmeter and pay careful attention it is very useful. However, the last few OEM voltmeters in vehicles I've owned only had markings at the extreme, so you had to "guess" where 14 volts was. One of my OEM voltmeters always seemed to drift higher on long trips, and this worried me. I thought it was some sort of alternator problem. I finally checked it with a real voltmeter and determined it was the gauge that was drifting. However, I don't suppose I could claim it was "faulty" since it was indicating a voltage somewhere between 11 and 18 volts, and it never got to the "red" on either end of the scale. I am very suspicious of the voltmeter in my current Nissan Frontier - it never moves when the truck is running. Either this truck has a super duper alternator, or the voltmeter is also a computer controlled gauge. I can't tell from the wiring diagram since the wiring harness just disappears into the IP module. If you really want to know what is going on with your electrical system, having both a voltmeter and an ammeter is better than either alone. With the voltmeter, you know the "pressure" in the system, with the ammeter you know the "flow" to and from the battery. If you have a good alternator, the voltmeter is always going to be in the 13.5 to 14.5 volt range with the vehicle running unless there is a major problem. If you also have an ammeter, and it shows significant current draws, even when most accessories are off, then you know you have a problem.
The article is wrong on one point - you don't have to run all the wires through an ammeter in your dash. There are remote sensing ammeters where the only thing transmitted to the gauge is an indicator voltage. You might want to look at http://www.siliconchip.com.au/cms/A_30551/article.html for an example of how this works. My old 800 Ford Tractor had an even simpler sort of ammeter. It did run the main power lead through the ammeter, but there was no physical break in the power lead. The ammeter had a loop that the main power lead ran through and this "detected" the current flow. With modern vehicles with scores of circuits this is impractical, but a remote senor like shown in the example on the web page can be applies at the main batter connection and transmit an indicator voltage to the dash gauge.
Ed White
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wrote:

Or fuel dilution (on a pre OBD2 engine - OBD2 will throw a code if an injector leaks- unless the engine isn't running) or oil viscosity breakdown (which has happened to me) or "foaming" which has happened on my brother's car - both due do crappy oil. Saved both engines by getting an oil change IMMEDIATELY upon noticing the pressure drop.
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[...]

I come from the world of heavy commercial truck repair. Never seen a pressure gauge or hose dump oil behind the dash. The electronic dashes use transducers that cost \$15 from the dealership and rarely fail and are always accurate within 2 or 3 psi when checked against my mechanical gauge. I have seen one inaccurate transducer; owner brought it in for low oil pressure. Everyone else who complains of low oil pressure needs an overhaul. Most drivers are too stupid to know what is or isn't good oil pressure, and I see quite a few drivers dump that lucas shit in the engine to get the psi higher. But I don't think that's a good argument to use an idiot light over a real gauge. I do not know of any commercial truck makers that equip \$20,000 engines with just idiot lights. All of the recent gauges are however equipped with an idiot light in addition to the needle. Comes on with low pressure, loss of signal, or excessively high signal. LED "bulb." Seems to me an optimum compromise. Needle for drivers who read the book, light for drivers who don't. Granted, it's a different market, where engines do routinely wear out simply due to mileage and most drivers do not own the driven vehicles. But direct-reading gauges aren't difficult or expensive.
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