Why not just 3000 miles?

Well, I guess if you drove 4 hours at day averaging 50 mph you could rack up 18,000 miles in 3 months.

Having both a time and a mileage limit would seem predicated on the fact that oil aging/contamination occurs both as a result of passage of calendar time (for example ingress from the enviornment) and as a result of run-time (for example wear particles).

I have never heard of anyone having a car engine fail because they were negligent in changing their oil (have you?). I wait until I can see or feel changes in the oil on the dipstick (dark or gritty) until I bother changing my car oil.

What if your grandmother only drove her car to 15 miles to church on Sundays? She’d only need to Change the oil every four years.

I think contamination of the oil is much worse before it gets to operating temperature which takes about 15 minutes.

Waylon, why are you in Lafayette now?

Folks,

How we drive the car and the conditions it sees are surely more important than either the miles or the months. Driving conditions in the Mohave desert are surely harsher than,say in a city, as far as the air filter and oil are concerned. Equally, a stop-start cycle in a downtown situation is harsh on brakes,clutches, engine, tires and transmission while it is less so on the freeway. And the driver - grandma vs 20 year old surely matters.

Using the oil condition itself to tell us when to change the oil will give optimal engine performance and cost the least.

Hest vwishes for the new Year.

V.Narayan.

quote:

Originally posted by Vee:
Using the oil condition itself to tell us when to change the oil will give optimal engine performance and cost the least.

Just like I said. "I wait until I can see or feel changes in the oil on the dipstick (dark or gritty) until I bother changing my car oil."

El-pete,

Is that the way you check your plant's machinery oil? Do you also use fingers instead of vibration measurements? Just half kidding!!!

Walt

Having worked at Amoco Labs Oil Division when I was much younger:

The time and mileage selection is actually based on older, pre-synthetic oils. Just as with other things, it has become a 'rule of thumb.' [BTW, historical fact - rule of thumb comes from an old law about how thick the stick or branch could be when 'correcting' your wife or children - no joke! Consider that next time you rely upon a rule of thumb...]

1. If you can feel the grit in your oil, then it is far too late. The particles that identify wear of the engine (not the condition of the oil) should be much, much smaller than that. You should be measuring the chemical breakdown of the additives and contamination in the oil.

2. (Does anyone know anyone who had a car fail due to oil?)- My father-in-law's van failed because he drove over 20,000 miles without an oil change. By the time he hit 80,000 miles, we took over the van and had the engine rebuilt. The build-up of sludge inside the engine was terrible. My brother borrowed my car while I was in the Navy and neglected to change the oil. He also neglected to check the oil level. The engine failed (bearings spun).

3. Older, non-synthetic (and some synthetic) oils 'settle.' This is where the additives within the oil begin to seperate out of the oil and it loses some of its properties.

Because of my experience with automotive oils (and the development of the Amoco Ultimate), I use synthetic oils in my vehicles and only change the oil every 7,000 to 8,000 miles (I do a lot of driving. New York City to Detroit or Chicago is not unusual.). The synthetic oils tend not to settle.

As the oil ages, in any case, you will begin to see fuel consumption go up due to friction.

Have fun!

Howard

Why not just 3000 miles

Someone could have used the motor for a winch on a ferry, or as a device to peel coconuts.

In most cases the next sentence is: whatever comes first

That is what the utilities think when they remove motors for overhauls every five years... whether they need the overhaul or not.

You are aware, of course, that one of the primary reasons for equipment failure is intrusive maintenance? The purpose of Condition-Based Maintenance and RCM is to ensure that the right maintenance is performed on the right equipment at the right time and for the right reasons.

Perhaps a sensor should be built into the vehicle, seeing that most new vehicles have more computer power than the space shuttle. The sensor would indicate the optimum time for an oil change based on the condition of the oil.

Let's see, four oil changes, minimum, per year, plus oil filter at least twice per year: ~$200+ per year. With sensor, perhaps an oil change once or twice per year, based upon the oil condition, driving, etc. With the cost of such a sensor built in, with programming, across a large number of vehicles, the cost may be insignificant and the engine may last longer.

After all, that is the thinking that was determined when RCM was conceived.

Howard

Funny that you would mention a sensor built into a vehicle for oil change. Went on vacation the last of December and rented a 2006 Chevy Impala. While looking over the instrumentation a screen came up that said 81% oil life left (or something like that). Not sure if this was based on mileage or oil condition. Should have read the manual I guess! Seems that if that is based on miles then condition should be an easy technology to adapt.

Given that the Impala is a typical GM product, then the oil life indicator is probably the GMOLS system, which is basically a small piece of firmware which runs in the engine control system processor. There is no physical sensor involved.

GMOLS measures miles driven vs "engine load factor", so if spend a lot of time start and stop driving in the city, or operating the engine at high temperatures, then your oil life will decrease faster than if you do lots of highway miles at a reasonable temperature.

This is all good - but the problem of oil contamination (dirt, glycol, fuel) or sludge buildup (through varnish, or an unfortunate mixing of different lubricant types) still remains unknown, and these problems are typically not directly related to mileage.

And if we look at RPM's...... 3000 miles on average 5 days service. Do you change oil every five days in your motor in plant operation?

It's all about contamination; ring blow-by, etc.

Your oil filter is in by-pass all the time and only and maybe 20% gets through the filter. AS the filter clogs then it may go to total by-pass.

How often do you change oil in the final drive, transmission, etc...???

There's an excellent article in the Oct 2005 issue of Lubes'n'Greases magazine (page 18) addressing this issue. Lots of stuff about GM's Oil Life System is included. The issue is online at www.lngpublishing.com. Hit the blue "click here" button in the yellow box on the homepage to get to the past issues.

quote:

Originally posted by Waylon M:
Why not just 3000 miles?

Nobody do it at 3000 miles!

By the time anyone gets to the mechanic shop, or when saturday morning arrives to change it by himself, the interval is over 3025 miles.

I just came across this old post, and have to say, people, buy yourselves european cars! Where synthetic oil is used over here, 2 years or 15,000 miles is quite common. My car, a Skoda, has a diesel engine with a variable servicing interval. It has a sensor in the sump, and only schedules a service when required, 18,000 miles last time. I was told that the sensor was a viscometer, but don't think this is likely as it can sense differnet chemical properties if you put differernt top-up oil in, and reduces the service interval accoringly.

I wanted to ask this question to see if there was some reason for changing oil at a time based interval regardless of operation induced problems. I was thinking of my grandmother when this question came to mind. Grandmother was told by her lawn mower sales man to change the oil in her mower after each yard mowing and her mower would last forever. Of course she was told to use their special oil manufactured for her particular brand of mower, which sells for double the price of conventional motor oil. There was no use in arguing with her about the salesman’s recommendations. However, the mower was in the family for over twelve years and never missed a beat. The mower was recently stolen. Most of us laughed about someone willing to steal the mower, which most of us felt had been more than a good return on the investment. As for grandmother’s reaction, you would have thought she had just purchased the thing.

tthew,
I recently asked a an expert in lubrication (this guy has over 30 years experience working for a major oil company) which aspect of an oil should be measured above all others (i.e particulate contamintion, water, viscosity, heat, additive depletion, etc). He very quickly answered viscosity, because almost any change in an oil's condition will result in a change in the oil's viscosity. If this is true, then there is reason to believe that Skoda did indeed install a viscometer in your type of car. Smart on their part. I wish cars sold in North America had this option.

I realise this thread has been inactive for a while, but I just had a reply from Skoda customer services about how the oil quality is measured for the variable sevicing interval,

"I can confirm that the sensor we use in the sump measures that amount of time that the oil takes to cool from hot and determines the quality of it."

Ever heard of a heating time test before anyone?

Not heard of a heating time before, but it is a very logical test, since viscosity tests are tied to temperature.
If you take a can of gearoil SAE 80, it will make a big difference if the test is conducted at 10, 15, 100 degrees of your favourite temperature scale.

If you are using a Saybolt viscometer, you pour some oil at a specified temperature in recipient, and fill through a calibrated pipe/orifice another calibrated recipient. The filling time is then called SSU, SSF etc.
If determining viscosity is bound to temperature and the basic test to time, a combination using temperature and time must give some related result.